From c1d885b0249f3978de3a21ea2bfb7ced06ed2aff Mon Sep 17 00:00:00 2001 From: Mattias Wadman Date: Fri, 12 Jul 2024 17:43:02 +0200 Subject: [PATCH] website: Make latest release (1.7) be default manual (#3130) Fixes issue with confusion about features that has not been released yet. Move deveopment manual.yml to dev/manual.yml Symlink manual.yml to v1.7/manual.yml Refactor to share history header with links to other manual versions. Change man.test and man page generation to use dev/manual.yml Related to #3078 #3127 --- Makefile.am | 8 +- docs/build_manpage.py | 2 +- docs/build_mantests.py | 2 +- docs/content/manual/dev/manual.yml | 3800 ++++++++++++++++++++++++++ docs/content/manual/manual.yml | 3806 +-------------------------- docs/content/manual/v1.3/manual.yml | 5 - docs/content/manual/v1.4/manual.yml | 5 - docs/content/manual/v1.5/manual.yml | 5 - docs/content/manual/v1.6/manual.yml | 5 - docs/content/manual/v1.7/manual.yml | 5 - docs/manual_schema.yml | 3 - docs/templates/manual.html.j2 | 12 +- 12 files changed, 3818 insertions(+), 3840 deletions(-) create mode 100644 docs/content/manual/dev/manual.yml mode change 100644 => 120000 docs/content/manual/manual.yml diff --git a/Makefile.am b/Makefile.am index f9594a5624..0b4b81e78e 100644 --- a/Makefile.am +++ b/Makefile.am @@ -160,10 +160,10 @@ check_DATA = tests/man.test # Making changes to the manpage without having the python deps means your # tests won't run. If you aren't making changes to the examples, you probably # don't care. But if you are, then you need to run the tests anyway. -tests/man.test tests/manonig.test: $(srcdir)/docs/content/manual/manual.yml +tests/man.test tests/manonig.test: $(srcdir)/docs/content/manual/dev/manual.yml if ENABLE_DOCS $(AM_V_GEN) ( cd ${abs_srcdir}/docs && \ - $(PIPENV) run python validate_manual_schema.py content/manual/manual.yml && \ + $(PIPENV) run python validate_manual_schema.py content/manual/dev/manual.yml && \ $(PIPENV) run python build_mantests.py ) else @echo Changes to the manual.yml require docs to be enabled to update the manual test. @@ -176,10 +176,10 @@ endif # manpage, then we'll end up using the cached version. Otherwise, we need to # rebuild it. man_MANS = jq.1 -jq.1.prebuilt: $(srcdir)/docs/content/manual/manual.yml +jq.1.prebuilt: $(srcdir)/docs/content/manual/dev/manual.yml if ENABLE_DOCS $(AM_V_GEN) ( cd ${abs_srcdir}/docs && \ - $(PIPENV) run python validate_manual_schema.py content/manual/manual.yml && \ + $(PIPENV) run python validate_manual_schema.py content/manual/dev/manual.yml && \ $(PIPENV) run python build_manpage.py ) > $@ else @echo Changes to the manual.yml require docs to be enabled to update the manpage. diff --git a/docs/build_manpage.py b/docs/build_manpage.py index becb451df6..da916cc5c3 100755 --- a/docs/build_manpage.py +++ b/docs/build_manpage.py @@ -209,7 +209,7 @@ def dedent_body(body): def convert_manual_to_markdown(): f = StringIO() - manual = load_yml_file("content/manual/manual.yml") + manual = load_yml_file("content/manual/dev/manual.yml") f.write(manual.get('manpage_intro', '\n')) f.write(dedent_body(manual.get('body', '\n'))) for section in manual.get('sections', []): diff --git a/docs/build_mantests.py b/docs/build_mantests.py index 925e14488b..bbc7e325bb 100755 --- a/docs/build_mantests.py +++ b/docs/build_mantests.py @@ -5,7 +5,7 @@ regex_program_pattern = re.compile( r'\b(?:test|match|capture|scan|split|splits|sub|gsub)\s*\(') -with open('content/manual/manual.yml') as source, \ +with open('content/manual/dev/manual.yml') as source, \ open('../tests/man.test', 'w') as man, \ open('../tests/manonig.test', 'w') as manonig: manual = yaml.safe_load(source) diff --git a/docs/content/manual/dev/manual.yml b/docs/content/manual/dev/manual.yml new file mode 100644 index 0000000000..1eb7d9b867 --- /dev/null +++ b/docs/content/manual/dev/manual.yml @@ -0,0 +1,3800 @@ +--- +headline: jq Manual (development version) + +body: | + + A jq program is a "filter": it takes an input, and produces an + output. There are a lot of builtin filters for extracting a + particular field of an object, or converting a number to a string, + or various other standard tasks. + + Filters can be combined in various ways - you can pipe the output of + one filter into another filter, or collect the output of a filter + into an array. + + Some filters produce multiple results, for instance there's one that + produces all the elements of its input array. Piping that filter + into a second runs the second filter for each element of the + array. Generally, things that would be done with loops and iteration + in other languages are just done by gluing filters together in jq. + + It's important to remember that every filter has an input and an + output. Even literals like "hello" or 42 are filters - they take an + input but always produce the same literal as output. Operations that + combine two filters, like addition, generally feed the same input to + both and combine the results. So, you can implement an averaging + filter as `add / length` - feeding the input array both to the `add` + filter and the `length` filter and then performing the division. + + But that's getting ahead of ourselves. :) Let's start with something + simpler: + +manpage_intro: | + jq(1) -- Command-line JSON processor + ==================================== + + ## SYNOPSIS + + `jq` [...] [...] + + `jq` can transform JSON in various ways, by selecting, iterating, + reducing and otherwise mangling JSON documents. For instance, + running the command `jq 'map(.price) | add'` will take an array of + JSON objects as input and return the sum of their "price" fields. + + `jq` can accept text input as well, but by default, `jq` reads a + stream of JSON entities (including numbers and other literals) from + `stdin`. Whitespace is only needed to separate entities such as 1 + and 2, and true and false. One or more may be specified, in + which case `jq` will read input from those instead. + + The are described in the [INVOKING JQ] section; they + mostly concern input and output formatting. The is written + in the jq language and specifies how to transform the input + file or document. + + ## FILTERS + +manpage_epilogue: | + ## BUGS + + Presumably. Report them or discuss them at: + + https://github.com/jqlang/jq/issues + + ## AUTHOR + + Stephen Dolan `` + +sections: + - title: Invoking jq + body: | + + jq filters run on a stream of JSON data. The input to jq is + parsed as a sequence of whitespace-separated JSON values which + are passed through the provided filter one at a time. The + output(s) of the filter are written to standard output, as a + sequence of newline-separated JSON data. + + The simplest and most common filter (or jq program) is `.`, + which is the identity operator, copying the inputs of the jq + processor to the output stream. Because the default behavior of + the jq processor is to read JSON texts from the input stream, + and to pretty-print outputs, the `.` program's main use is to + validate and pretty-print the inputs. The jq programming + language is quite rich and allows for much more than just + validation and pretty-printing. + + Note: it is important to mind the shell's quoting rules. As a + general rule it's best to always quote (with single-quote + characters on Unix shells) the jq program, as too many characters with special + meaning to jq are also shell meta-characters. For example, `jq + "foo"` will fail on most Unix shells because that will be the same + as `jq foo`, which will generally fail because `foo is not + defined`. When using the Windows command shell (cmd.exe) it's + best to use double quotes around your jq program when given on the + command-line (instead of the `-f program-file` option), but then + double-quotes in the jq program need backslash escaping. When using + the Powershell (`powershell.exe`) or the Powershell Core + (`pwsh`/`pwsh.exe`), use single-quote characters around the jq + program and backslash-escaped double-quotes (`\"`) inside the jq + program. + + * Unix shells: `jq '.["foo"]'` + * Powershell: `jq '.[\"foo\"]'` + * Windows command shell: `jq ".[\"foo\"]"` + + Note: jq allows user-defined functions, but every jq program + must have a top-level expression. + + You can affect how jq reads and writes its input and output + using some command-line options: + + * `--null-input` / `-n`: + + Don't read any input at all. Instead, the filter is run once + using `null` as the input. This is useful when using jq as a + simple calculator or to construct JSON data from scratch. + + * `--raw-input` / `-R`: + + Don't parse the input as JSON. Instead, each line of text is + passed to the filter as a string. If combined with `--slurp`, + then the entire input is passed to the filter as a single long + string. + + * `--slurp` / `-s`: + + Instead of running the filter for each JSON object in the + input, read the entire input stream into a large array and run + the filter just once. + + * `--compact-output` / `-c`: + + By default, jq pretty-prints JSON output. Using this option + will result in more compact output by instead putting each + JSON object on a single line. + + * `--raw-output` / `-r`: + + With this option, if the filter's result is a string then it + will be written directly to standard output rather than being + formatted as a JSON string with quotes. This can be useful for + making jq filters talk to non-JSON-based systems. + + * `--raw-output0`: + + Like `-r` but jq will print NUL instead of newline after each output. + This can be useful when the values being output can contain newlines. + When the output value contains NUL, jq exits with non-zero code. + + * `--join-output` / `-j`: + + Like `-r` but jq won't print a newline after each output. + + * `--ascii-output` / `-a`: + + jq usually outputs non-ASCII Unicode codepoints as UTF-8, even + if the input specified them as escape sequences (like + "\u03bc"). Using this option, you can force jq to produce pure + ASCII output with every non-ASCII character replaced with the + equivalent escape sequence. + + * `--sort-keys` / `-S`: + + Output the fields of each object with the keys in sorted order. + + * `--color-output` / `-C` and `--monochrome-output` / `-M`: + + By default, jq outputs colored JSON if writing to a + terminal. You can force it to produce color even if writing to + a pipe or a file using `-C`, and disable color with `-M`. + When the `NO_COLOR` environment variable is not empty, jq disables + colored output by default, but you can enable it by `-C`. + + Colors can be configured with the `JQ_COLORS` environment + variable (see below). + + * `--tab`: + + Use a tab for each indentation level instead of two spaces. + + * `--indent n`: + + Use the given number of spaces (no more than 7) for indentation. + + * `--unbuffered`: + + Flush the output after each JSON object is printed (useful if + you're piping a slow data source into jq and piping jq's + output elsewhere). + + * `--stream`: + + Parse the input in streaming fashion, outputting arrays of path + and leaf values (scalars and empty arrays or empty objects). + For example, `"a"` becomes `[[],"a"]`, and `[[],"a",["b"]]` + becomes `[[0],[]]`, `[[1],"a"]`, and `[[2,0],"b"]`. + + This is useful for processing very large inputs. Use this in + conjunction with filtering and the `reduce` and `foreach` syntax + to reduce large inputs incrementally. + + * `--stream-errors`: + + Like `--stream`, but invalid JSON inputs yield array values + where the first element is the error and the second is a path. + For example, `["a",n]` produces `["Invalid literal at line 1, + column 7",[1]]`. + + Implies `--stream`. Invalid JSON inputs produce no error values + when `--stream` without `--stream-errors`. + + * `--seq`: + + Use the `application/json-seq` MIME type scheme for separating + JSON texts in jq's input and output. This means that an ASCII + RS (record separator) character is printed before each value on + output and an ASCII LF (line feed) is printed after every + output. Input JSON texts that fail to parse are ignored (but + warned about), discarding all subsequent input until the next + RS. This mode also parses the output of jq without the `--seq` + option. + + * `-f filename` / `--from-file filename`: + + Read filter from the file rather than from a command line, like + awk's -f option. + + * `-L directory`: + + Prepend `directory` to the search list for modules. If this + option is used then no builtin search list is used. See the + section on modules below. + + * `--arg name value`: + + This option passes a value to the jq program as a predefined + variable. If you run jq with `--arg foo bar`, then `$foo` is + available in the program and has the value `"bar"`. Note that + `value` will be treated as a string, so `--arg foo 123` will + bind `$foo` to `"123"`. + + Named arguments are also available to the jq program as + `$ARGS.named`. + + * `--argjson name JSON-text`: + + This option passes a JSON-encoded value to the jq program as a + predefined variable. If you run jq with `--argjson foo 123`, then + `$foo` is available in the program and has the value `123`. + + * `--slurpfile variable-name filename`: + + This option reads all the JSON texts in the named file and binds + an array of the parsed JSON values to the given global variable. + If you run jq with `--slurpfile foo bar`, then `$foo` is available + in the program and has an array whose elements correspond to the + texts in the file named `bar`. + + * `--rawfile variable-name filename`: + + This option reads in the named file and binds its contents to the given + global variable. If you run jq with `--rawfile foo bar`, then `$foo` is + available in the program and has a string whose contents are to the texts + in the file named `bar`. + + * `--args`: + + Remaining arguments are positional string arguments. These are + available to the jq program as `$ARGS.positional[]`. + + * `--jsonargs`: + + Remaining arguments are positional JSON text arguments. These + are available to the jq program as `$ARGS.positional[]`. + + * `--exit-status` / `-e`: + + Sets the exit status of jq to 0 if the last output value was + neither `false` nor `null`, 1 if the last output value was + either `false` or `null`, or 4 if no valid result was ever + produced. Normally jq exits with 2 if there was any usage + problem or system error, 3 if there was a jq program compile + error, or 0 if the jq program ran. + + Another way to set the exit status is with the `halt_error` + builtin function. + + * `--binary` / `-b`: + + Windows users using WSL, MSYS2, or Cygwin, should use this option + when using a native jq.exe, otherwise jq will turn newlines (LFs) + into carriage-return-then-newline (CRLF). + + * `--version` / `-V`: + + Output the jq version and exit with zero. + + * `--build-configuration`: + + Output the build configuration of jq and exit with zero. + This output has no supported format or structure and may change + without notice in future releases. + + * `--help` / `-h`: + + Output the jq help and exit with zero. + + * `--`: + + Terminates argument processing. Remaining arguments are not + interpreted as options. + + * `--run-tests [filename]`: + + Runs the tests in the given file or standard input. This must + be the last option given and does not honor all preceding + options. The input consists of comment lines, empty lines, and + program lines followed by one input line, as many lines of + output as are expected (one per output), and a terminating empty + line. Compilation failure tests start with a line containing + only `%%FAIL`, then a line containing the program to compile, + then a line containing an error message to compare to the + actual. + + Be warned that this option can change backwards-incompatibly. + + - title: Basic filters + entries: + - title: "Identity: `.`" + body: | + + The absolute simplest filter is `.` . This filter takes its + input and produces the same value as output. That is, this + is the identity operator. + + Since jq by default pretty-prints all output, a trivial + program consisting of nothing but `.` can be used to format + JSON output from, say, `curl`. + + Although the identity filter never modifies the value of its + input, jq processing can sometimes make it appear as though + it does. For example, using the current implementation of + jq, we would see that the expression: + + 1E1234567890 | . + + produces `1.7976931348623157e+308` on at least one platform. + This is because, in the process of parsing the number, this + particular version of jq has converted it to an IEEE754 + double-precision representation, losing precision. + + The way in which jq handles numbers has changed over time + and further changes are likely within the parameters set by + the relevant JSON standards. Moreover, build configuration + options can alter how jq processes numbers. + + The following remarks are therefore offered with the + understanding that they are intended to be descriptive of the + current version of jq and should not be interpreted as being + prescriptive: + + (1) Any arithmetic operation on a number that has not + already been converted to an IEEE754 double precision + representation will trigger a conversion to the IEEE754 + representation. + + (2) jq will attempt to maintain the original decimal + precision of number literals (if the `--disable-decnum` + build configuration option was not used), but in expressions + such `1E1234567890`, precision will be lost if the exponent + is too large. + + (3) In jq programs, a leading minus sign will trigger the + conversion of the number to an IEEE754 representation. + + (4) Comparisons are carried out using the untruncated + big decimal representation of numbers if available, as + illustrated in one of the following examples. + + The examples below use the builtin function `have_decnum` in + order to demonstrate the expected effects of using / not + using the `--disable-decnum` build configuration option, and + also to allow automated tests derived from these examples to + pass regardless of whether that option is used. + + examples: + - program: '.' + input: '"Hello, world!"' + output: ['"Hello, world!"'] + + - program: '.' + input: '0.12345678901234567890123456789' + output: ['0.12345678901234567890123456789'] + + - program: '[., tojson] | . == if have_decnum then [12345678909876543212345,"12345678909876543212345"] else [12345678909876543000000,"12345678909876543000000"] end' + input: '12345678909876543212345' + output: ['true'] + + - program: '. < 0.12345678901234567890123456788' + input: '0.12345678901234567890123456789' + output: ['false'] + + - program: 'map([., . == 1]) | tojson | . == if have_decnum then "[[1,true],[1.000,true],[1.0,true],[1.00,true]]" else "[[1,true],[1,true],[1,true],[1,true]]" end' + input: '[1, 1.000, 1.0, 100e-2]' + output: ['true'] + + - program: '. as $big | [$big, $big + 1] | map(. > 10000000000000000000000000000000) | . == if have_decnum then [true, false] else [false, false] end' + input: '10000000000000000000000000000001' + output: ['true'] + + - title: "Object Identifier-Index: `.foo`, `.foo.bar`" + body: | + + The simplest *useful* filter has the form `.foo`. When given a + JSON object (aka dictionary or hash) as input, `.foo` produces + the value at the key "foo" if the key is present, or null otherwise. + + A filter of the form `.foo.bar` is equivalent to `.foo | .bar`. + + The `.foo` syntax only works for simple, identifier-like keys, that + is, keys that are all made of alphanumeric characters and + underscore, and which do not start with a digit. + + If the key contains special characters or starts with a digit, + you need to surround it with double quotes like this: + `."foo$"`, or else `.["foo$"]`. + + For example `.["foo::bar"]` and `.["foo.bar"]` work while + `.foo::bar` does not. + + examples: + - program: '.foo' + input: '{"foo": 42, "bar": "less interesting data"}' + output: ['42'] + + - program: '.foo' + input: '{"notfoo": true, "alsonotfoo": false}' + output: ['null'] + + - program: '.["foo"]' + input: '{"foo": 42}' + output: ['42'] + + - title: "Optional Object Identifier-Index: `.foo?`" + body: | + + Just like `.foo`, but does not output an error when `.` is not an + object. + + examples: + - program: '.foo?' + input: '{"foo": 42, "bar": "less interesting data"}' + output: ['42'] + - program: '.foo?' + input: '{"notfoo": true, "alsonotfoo": false}' + output: ['null'] + - program: '.["foo"]?' + input: '{"foo": 42}' + output: ['42'] + - program: '[.foo?]' + input: '[1,2]' + output: ['[]'] + + - title: "Object Index: `.[]`" + body: | + + You can also look up fields of an object using syntax like + `.["foo"]` (`.foo` above is a shorthand version of this, but + only for identifier-like strings). + + - title: "Array Index: `.[]`" + body: | + + When the index value is an integer, `.[]` can index + arrays. Arrays are zero-based, so `.[2]` returns the third + element. + + Negative indices are allowed, with -1 referring to the last + element, -2 referring to the next to last element, and so on. + + examples: + - program: '.[0]' + input: '[{"name":"JSON", "good":true}, {"name":"XML", "good":false}]' + output: ['{"name":"JSON", "good":true}'] + + - program: '.[2]' + input: '[{"name":"JSON", "good":true}, {"name":"XML", "good":false}]' + output: ['null'] + + - program: '.[-2]' + input: '[1,2,3]' + output: ['2'] + + - title: "Array/String Slice: `.[:]`" + body: | + + The `.[:]` syntax can be used to return a + subarray of an array or substring of a string. The array + returned by `.[10:15]` will be of length 5, containing the + elements from index 10 (inclusive) to index 15 (exclusive). + Either index may be negative (in which case it counts + backwards from the end of the array), or omitted (in which + case it refers to the start or end of the array). + Indices are zero-based. + + examples: + - program: '.[2:4]' + input: '["a","b","c","d","e"]' + output: ['["c", "d"]'] + + - program: '.[2:4]' + input: '"abcdefghi"' + output: ['"cd"'] + + - program: '.[:3]' + input: '["a","b","c","d","e"]' + output: ['["a", "b", "c"]'] + + - program: '.[-2:]' + input: '["a","b","c","d","e"]' + output: ['["d", "e"]'] + + - title: "Array/Object Value Iterator: `.[]`" + body: | + + If you use the `.[index]` syntax, but omit the index + entirely, it will return *all* of the elements of an + array. Running `.[]` with the input `[1,2,3]` will produce the + numbers as three separate results, rather than as a single + array. A filter of the form `.foo[]` is equivalent to + `.foo | .[]`. + + You can also use this on an object, and it will return all + the values of the object. + + Note that the iterator operator is a generator of values. + + examples: + - program: '.[]' + input: '[{"name":"JSON", "good":true}, {"name":"XML", "good":false}]' + output: + - '{"name":"JSON", "good":true}' + - '{"name":"XML", "good":false}' + + - program: '.[]' + input: '[]' + output: [] + + - program: '.foo[]' + input: '{"foo":[1,2,3]}' + output: ['1','2','3'] + + - program: '.[]' + input: '{"a": 1, "b": 1}' + output: ['1', '1'] + + - title: "`.[]?`" + body: | + + Like `.[]`, but no errors will be output if . is not an array + or object. A filter of the form `.foo[]?` is equivalent to + `.foo | .[]?`. + + - title: "Comma: `,`" + body: | + + If two filters are separated by a comma, then the + same input will be fed into both and the two filters' output + value streams will be concatenated in order: first, all of the + outputs produced by the left expression, and then all of the + outputs produced by the right. For instance, filter `.foo, + .bar`, produces both the "foo" fields and "bar" fields as + separate outputs. + + The `,` operator is one way to construct generators. + + examples: + - program: '.foo, .bar' + input: '{"foo": 42, "bar": "something else", "baz": true}' + output: ['42', '"something else"'] + + - program: ".user, .projects[]" + input: '{"user":"stedolan", "projects": ["jq", "wikiflow"]}' + output: ['"stedolan"', '"jq"', '"wikiflow"'] + + - program: '.[4,2]' + input: '["a","b","c","d","e"]' + output: ['"e"', '"c"'] + + - title: "Pipe: `|`" + body: | + + The | operator combines two filters by feeding the output(s) of + the one on the left into the input of the one on the right. It's + similar to the Unix shell's pipe, if you're used to that. + + If the one on the left produces multiple results, the one on + the right will be run for each of those results. So, the + expression `.[] | .foo` retrieves the "foo" field of each + element of the input array. This is a cartesian product, + which can be surprising. + + Note that `.a.b.c` is the same as `.a | .b | .c`. + + Note too that `.` is the input value at the particular stage + in a "pipeline", specifically: where the `.` expression appears. + Thus `.a | . | .b` is the same as `.a.b`, as the `.` in the + middle refers to whatever value `.a` produced. + + examples: + - program: '.[] | .name' + input: '[{"name":"JSON", "good":true}, {"name":"XML", "good":false}]' + output: ['"JSON"', '"XML"'] + + - title: "Parenthesis" + body: | + + Parenthesis work as a grouping operator just as in any typical + programming language. + + examples: + - program: '(. + 2) * 5' + input: '1' + output: ['15'] + + - title: Types and Values + body: | + + jq supports the same set of datatypes as JSON - numbers, + strings, booleans, arrays, objects (which in JSON-speak are + hashes with only string keys), and "null". + + Booleans, null, strings and numbers are written the same way as + in JSON. Just like everything else in jq, these simple + values take an input and produce an output - `42` is a valid jq + expression that takes an input, ignores it, and returns 42 + instead. + + Numbers in jq are internally represented by their IEEE754 double + precision approximation. Any arithmetic operation with numbers, + whether they are literals or results of previous filters, will + produce a double precision floating point result. + + However, when parsing a literal jq will store the original literal + string. If no mutation is applied to this value then it will make + to the output in its original form, even if conversion to double + would result in a loss. + + entries: + - title: "Array construction: `[]`" + body: | + + As in JSON, `[]` is used to construct arrays, as in + `[1,2,3]`. The elements of the arrays can be any jq + expression, including a pipeline. All of the results produced + by all of the expressions are collected into one big array. + You can use it to construct an array out of a known quantity + of values (as in `[.foo, .bar, .baz]`) or to "collect" all the + results of a filter into an array (as in `[.items[].name]`) + + Once you understand the "," operator, you can look at jq's array + syntax in a different light: the expression `[1,2,3]` is not using a + built-in syntax for comma-separated arrays, but is instead applying + the `[]` operator (collect results) to the expression 1,2,3 (which + produces three different results). + + If you have a filter `X` that produces four results, + then the expression `[X]` will produce a single result, an + array of four elements. + + examples: + - program: "[.user, .projects[]]" + input: '{"user":"stedolan", "projects": ["jq", "wikiflow"]}' + output: ['["stedolan", "jq", "wikiflow"]'] + - program: "[ .[] | . * 2]" + input: '[1, 2, 3]' + output: ['[2, 4, 6]'] + + - title: "Object Construction: `{}`" + body: | + + Like JSON, `{}` is for constructing objects (aka + dictionaries or hashes), as in: `{"a": 42, "b": 17}`. + + If the keys are "identifier-like", then the quotes can be left + off, as in `{a:42, b:17}`. Variable references as key + expressions use the value of the variable as the key. Key + expressions other than constant literals, identifiers, or + variable references, need to be parenthesized, e.g., + `{("a"+"b"):59}`. + + The value can be any expression (although you may need to wrap + it in parentheses if, for example, it contains colons), which + gets applied to the {} expression's input (remember, all + filters have an input and an output). + + {foo: .bar} + + will produce the JSON object `{"foo": 42}` if given the JSON + object `{"bar":42, "baz":43}` as its input. You can use this + to select particular fields of an object: if the input is an + object with "user", "title", "id", and "content" fields and + you just want "user" and "title", you can write + + {user: .user, title: .title} + + Because that is so common, there's a shortcut syntax for it: + `{user, title}`. + + If one of the expressions produces multiple results, + multiple dictionaries will be produced. If the input's + + {"user":"stedolan","titles":["JQ Primer", "More JQ"]} + + then the expression + + {user, title: .titles[]} + + will produce two outputs: + + {"user":"stedolan", "title": "JQ Primer"} + {"user":"stedolan", "title": "More JQ"} + + Putting parentheses around the key means it will be evaluated as an + expression. With the same input as above, + + {(.user): .titles} + + produces + + {"stedolan": ["JQ Primer", "More JQ"]} + + Variable references as keys use the value of the variable as + the key. Without a value then the variable's name becomes the + key and its value becomes the value, + + "f o o" as $foo | "b a r" as $bar | {$foo, $bar:$foo} + + produces + + {"foo":"f o o","b a r":"f o o"} + + examples: + - program: '{user, title: .titles[]}' + input: '{"user":"stedolan","titles":["JQ Primer", "More JQ"]}' + output: + - '{"user":"stedolan", "title": "JQ Primer"}' + - '{"user":"stedolan", "title": "More JQ"}' + - program: '{(.user): .titles}' + input: '{"user":"stedolan","titles":["JQ Primer", "More JQ"]}' + output: ['{"stedolan": ["JQ Primer", "More JQ"]}'] + + - title: "Recursive Descent: `..`" + body: | + + Recursively descends `.`, producing every value. This is the + same as the zero-argument `recurse` builtin (see below). This + is intended to resemble the XPath `//` operator. Note that + `..a` does not work; use `.. | .a` instead. In the example + below we use `.. | .a?` to find all the values of object keys + "a" in any object found "below" `.`. + + This is particularly useful in conjunction with `path(EXP)` + (also see below) and the `?` operator. + + examples: + - program: '.. | .a?' + input: '[[{"a":1}]]' + output: ['1'] + + - title: Builtin operators and functions + body: | + + Some jq operators (for instance, `+`) do different things + depending on the type of their arguments (arrays, numbers, + etc.). However, jq never does implicit type conversions. If you + try to add a string to an object you'll get an error message and + no result. + + Please note that all numbers are converted to IEEE754 double precision + floating point representation. Arithmetic and logical operators are working + with these converted doubles. Results of all such operations are also limited + to the double precision. + + The only exception to this behaviour of number is a snapshot of original number + literal. When a number which originally was provided as a literal is never + mutated until the end of the program then it is printed to the output in its + original literal form. This also includes cases when the original literal + would be truncated when converted to the IEEE754 double precision floating point + number. + + entries: + - title: "Addition: `+`" + body: | + + The operator `+` takes two filters, applies them both + to the same input, and adds the results together. What + "adding" means depends on the types involved: + + - **Numbers** are added by normal arithmetic. + + - **Arrays** are added by being concatenated into a larger array. + + - **Strings** are added by being joined into a larger string. + + - **Objects** are added by merging, that is, inserting all + the key-value pairs from both objects into a single + combined object. If both objects contain a value for the + same key, the object on the right of the `+` wins. (For + recursive merge use the `*` operator.) + + `null` can be added to any value, and returns the other + value unchanged. + + examples: + - program: '.a + 1' + input: '{"a": 7}' + output: ['8'] + - program: '.a + .b' + input: '{"a": [1,2], "b": [3,4]}' + output: ['[1,2,3,4]'] + - program: '.a + null' + input: '{"a": 1}' + output: ['1'] + - program: '.a + 1' + input: '{}' + output: ['1'] + - program: '{a: 1} + {b: 2} + {c: 3} + {a: 42}' + input: 'null' + output: ['{"a": 42, "b": 2, "c": 3}'] + + - title: "Subtraction: `-`" + body: | + + As well as normal arithmetic subtraction on numbers, the `-` + operator can be used on arrays to remove all occurrences of + the second array's elements from the first array. + + examples: + - program: '4 - .a' + input: '{"a":3}' + output: ['1'] + - program: . - ["xml", "yaml"] + input: '["xml", "yaml", "json"]' + output: ['["json"]'] + + - title: "Multiplication, division, modulo: `*`, `/`, `%`" + body: | + + These infix operators behave as expected when given two numbers. + Division by zero raises an error. `x % y` computes x modulo y. + + Multiplying a string by a number produces the concatenation of + that string that many times. `"x" * 0` produces `""`. + + Dividing a string by another splits the first using the second + as separators. + + Multiplying two objects will merge them recursively: this works + like addition but if both objects contain a value for the + same key, and the values are objects, the two are merged with + the same strategy. + + examples: + - program: '10 / . * 3' + input: '5' + output: ['6'] + - program: '. / ", "' + input: '"a, b,c,d, e"' + output: ['["a","b,c,d","e"]'] + - program: '{"k": {"a": 1, "b": 2}} * {"k": {"a": 0,"c": 3}}' + input: 'null' + output: ['{"k": {"a": 0, "b": 2, "c": 3}}'] + - program: '.[] | (1 / .)?' + input: '[1,0,-1]' + output: ['1', '-1'] + + - title: "`abs`" + body: | + + The builtin function `abs` is defined naively as: `if . < 0 then - . else . end`. + + For numeric input, this is the absolute value. See the + section on the identity filter for the implications of this + definition for numeric input. + + To compute the absolute value of a number as a floating point number, you may wish use `fabs`. + + examples: + - program: 'map(abs)' + input: '[-10, -1.1, -1e-1]' + output: ['[10,1.1,1e-1]'] + + - title: "`length`" + body: | + + The builtin function `length` gets the length of various + different types of value: + + - The length of a **string** is the number of Unicode + codepoints it contains (which will be the same as its + JSON-encoded length in bytes if it's pure ASCII). + + - The length of a **number** is its absolute value. + + - The length of an **array** is the number of elements. + + - The length of an **object** is the number of key-value pairs. + + - The length of **null** is zero. + + - It is an error to use `length` on a **boolean**. + + examples: + - program: '.[] | length' + input: '[[1,2], "string", {"a":2}, null, -5]' + output: ['2', '6', '1', '0', '5'] + + + - title: "`utf8bytelength`" + body: | + + The builtin function `utf8bytelength` outputs the number of + bytes used to encode a string in UTF-8. + + examples: + - program: 'utf8bytelength' + input: '"\u03bc"' + output: ['2'] + + - title: "`keys`, `keys_unsorted`" + body: | + + The builtin function `keys`, when given an object, returns + its keys in an array. + + The keys are sorted "alphabetically", by unicode codepoint + order. This is not an order that makes particular sense in + any particular language, but you can count on it being the + same for any two objects with the same set of keys, + regardless of locale settings. + + When `keys` is given an array, it returns the valid indices + for that array: the integers from 0 to length-1. + + The `keys_unsorted` function is just like `keys`, but if + the input is an object then the keys will not be sorted, + instead the keys will roughly be in insertion order. + + examples: + - program: 'keys' + input: '{"abc": 1, "abcd": 2, "Foo": 3}' + output: ['["Foo", "abc", "abcd"]'] + - program: 'keys' + input: '[42,3,35]' + output: ['[0,1,2]'] + + - title: "`has(key)`" + body: | + + The builtin function `has` returns whether the input object + has the given key, or the input array has an element at the + given index. + + `has($key)` has the same effect as checking whether `$key` + is a member of the array returned by `keys`, although `has` + will be faster. + + examples: + - program: 'map(has("foo"))' + input: '[{"foo": 42}, {}]' + output: ['[true, false]'] + - program: 'map(has(2))' + input: '[[0,1], ["a","b","c"]]' + output: ['[false, true]'] + + - title: "`in`" + body: | + + The builtin function `in` returns whether or not the input key is in the + given object, or the input index corresponds to an element + in the given array. It is, essentially, an inversed version + of `has`. + + examples: + - program: '.[] | in({"foo": 42})' + input: '["foo", "bar"]' + output: ['true', 'false'] + - program: 'map(in([0,1]))' + input: '[2, 0]' + output: ['[false, true]'] + + - title: "`map(f)`, `map_values(f)`" + body: | + + For any filter `f`, `map(f)` and `map_values(f)` apply `f` + to each of the values in the input array or object, that is, + to the values of `.[]`. + + In the absence of errors, `map(f)` always outputs an array + whereas `map_values(f)` outputs an array if given an array, + or an object if given an object. + + When the input to `map_values(f)` is an object, the output + object has the same keys as the input object except for + those keys whose values when piped to `f` produce no values + at all. + + The key difference between `map(f)` and `map_values(f)` is + that the former simply forms an array from all the values of + `($x|f)` for each value, $x, in the input array or object, + but `map_values(f)` only uses `first($x|f)`. + + Specifically, for object inputs, `map_values(f)` constructs + the output object by examining in turn the value of + `first(.[$k]|f)` for each key, $k, of the input. If this + expression produces no values, then the corresponding key + will be dropped; otherwise, the output object will have that + value at the key, $k. + + Here are some examples to clarify the behavior of `map` and + `map_values` when applied to arrays. These examples assume the + input is `[1]` in all cases: + + map(.+1) #=> [2] + map(., .) #=> [1,1] + map(empty) #=> [] + + map_values(.+1) #=> [2] + map_values(., .) #=> [1] + map_values(empty) #=> [] + + `map(f)` is equivalent to `[.[] | f]` and + `map_values(f)` is equivalent to `.[] |= f`. + + In fact, these are their implementations. + + + examples: + - program: 'map(.+1)' + input: '[1,2,3]' + output: ['[2,3,4]'] + + - program: 'map_values(.+1)' + input: '{"a": 1, "b": 2, "c": 3}' + output: ['{"a": 2, "b": 3, "c": 4}'] + + - program: 'map(., .)' + input: '[1,2]' + output: ['[1,1,2,2]'] + + - program: 'map_values(. // empty)' + input: '{"a": null, "b": true, "c": false}' + output: ['{"b":true}'] + + + - title: "`pick(pathexps)`" + body: | + + Emit the projection of the input object or array defined by the + specified sequence of path expressions, such that if `p` is any + one of these specifications, then `(. | p)` will evaluate to the + same value as `(. | pick(pathexps) | p)`. For arrays, negative + indices and `.[m:n]` specifications should not be used. + + examples: + - program: 'pick(.a, .b.c, .x)' + input: '{"a": 1, "b": {"c": 2, "d": 3}, "e": 4}' + output: ['{"a":1,"b":{"c":2},"x":null}'] + + - program: 'pick(.[2], .[0], .[0])' + input: '[1,2,3,4]' + output: ['[1,null,3]'] + + + - title: "`path(path_expression)`" + body: | + + Outputs array representations of the given path expression + in `.`. The outputs are arrays of strings (object keys) + and/or numbers (array indices). + + Path expressions are jq expressions like `.a`, but also `.[]`. + There are two types of path expressions: ones that can match + exactly, and ones that cannot. For example, `.a.b.c` is an + exact match path expression, while `.a[].b` is not. + + `path(exact_path_expression)` will produce the array + representation of the path expression even if it does not + exist in `.`, if `.` is `null` or an array or an object. + + `path(pattern)` will produce array representations of the + paths matching `pattern` if the paths exist in `.`. + + Note that the path expressions are not different from normal + expressions. The expression + `path(..|select(type=="boolean"))` outputs all the paths to + boolean values in `.`, and only those paths. + + examples: + - program: 'path(.a[0].b)' + input: 'null' + output: ['["a",0,"b"]'] + - program: '[path(..)]' + input: '{"a":[{"b":1}]}' + output: ['[[],["a"],["a",0],["a",0,"b"]]'] + + - title: "`del(path_expression)`" + body: | + + The builtin function `del` removes a key and its corresponding + value from an object. + + examples: + - program: 'del(.foo)' + input: '{"foo": 42, "bar": 9001, "baz": 42}' + output: ['{"bar": 9001, "baz": 42}'] + - program: 'del(.[1, 2])' + input: '["foo", "bar", "baz"]' + output: ['["foo"]'] + + - title: "`getpath(PATHS)`" + body: | + + The builtin function `getpath` outputs the values in `.` found + at each path in `PATHS`. + + examples: + - program: 'getpath(["a","b"])' + input: 'null' + output: ['null'] + - program: '[getpath(["a","b"], ["a","c"])]' + input: '{"a":{"b":0, "c":1}}' + output: ['[0, 1]'] + + - title: "`setpath(PATHS; VALUE)`" + body: | + + The builtin function `setpath` sets the `PATHS` in `.` to `VALUE`. + + examples: + - program: 'setpath(["a","b"]; 1)' + input: 'null' + output: ['{"a": {"b": 1}}'] + - program: 'setpath(["a","b"]; 1)' + input: '{"a":{"b":0}}' + output: ['{"a": {"b": 1}}'] + - program: 'setpath([0,"a"]; 1)' + input: 'null' + output: ['[{"a":1}]'] + + - title: "`delpaths(PATHS)`" + body: | + + The builtin function `delpaths` deletes the `PATHS` in `.`. + `PATHS` must be an array of paths, where each path is an array + of strings and numbers. + + examples: + - program: 'delpaths([["a","b"]])' + input: '{"a":{"b":1},"x":{"y":2}}' + output: ['{"a":{},"x":{"y":2}}'] + + - title: "`to_entries`, `from_entries`, `with_entries(f)`" + body: | + + These functions convert between an object and an array of + key-value pairs. If `to_entries` is passed an object, then + for each `k: v` entry in the input, the output array + includes `{"key": k, "value": v}`. + + `from_entries` does the opposite conversion, and `with_entries(f)` + is a shorthand for `to_entries | map(f) | from_entries`, useful for + doing some operation to all keys and values of an object. + `from_entries` accepts `"key"`, `"Key"`, `"name"`, `"Name"`, + `"value"`, and `"Value"` as keys. + + examples: + - program: 'to_entries' + input: '{"a": 1, "b": 2}' + output: ['[{"key":"a", "value":1}, {"key":"b", "value":2}]'] + - program: 'from_entries' + input: '[{"key":"a", "value":1}, {"key":"b", "value":2}]' + output: ['{"a": 1, "b": 2}'] + - program: 'with_entries(.key |= "KEY_" + .)' + input: '{"a": 1, "b": 2}' + output: ['{"KEY_a": 1, "KEY_b": 2}'] + + + - title: "`select(boolean_expression)`" + body: | + + The function `select(f)` produces its input unchanged if + `f` returns true for that input, and produces no output + otherwise. + + It's useful for filtering lists: `[1,2,3] | map(select(. >= 2))` + will give you `[2,3]`. + + examples: + - program: 'map(select(. >= 2))' + input: '[1,5,3,0,7]' + output: ['[5,3,7]'] + - program: '.[] | select(.id == "second")' + input: '[{"id": "first", "val": 1}, {"id": "second", "val": 2}]' + output: ['{"id": "second", "val": 2}'] + + + - title: "`arrays`, `objects`, `iterables`, `booleans`, `numbers`, `normals`, `finites`, `strings`, `nulls`, `values`, `scalars`" + body: | + + These built-ins select only inputs that are arrays, objects, + iterables (arrays or objects), booleans, numbers, normal + numbers, finite numbers, strings, null, non-null values, and + non-iterables, respectively. + + examples: + - program: '.[]|numbers' + input: '[[],{},1,"foo",null,true,false]' + output: ['1'] + + - title: "`empty`" + body: | + + `empty` returns no results. None at all. Not even `null`. + + It's useful on occasion. You'll know if you need it :) + + examples: + - program: '1, empty, 2' + input: 'null' + output: ['1', '2'] + - program: '[1,2,empty,3]' + input: 'null' + output: ['[1,2,3]'] + + - title: "`error`, `error(message)`" + body: | + + Produces an error with the input value, or with the message + given as the argument. Errors can be caught with try/catch; + see below. + + examples: + - program: 'try error catch .' + input: '"error message"' + output: ['"error message"'] + + - program: 'try error("invalid value: \(.)") catch .' + input: '42' + output: ['"invalid value: 42"'] + + - title: "`halt`" + body: | + + Stops the jq program with no further outputs. jq will exit + with exit status `0`. + + - title: "`halt_error`, `halt_error(exit_code)`" + body: | + + Stops the jq program with no further outputs. The input will + be printed on `stderr` as raw output (i.e., strings will not + have double quotes) with no decoration, not even a newline. + + The given `exit_code` (defaulting to `5`) will be jq's exit + status. + + For example, `"Error: something went wrong\n"|halt_error(1)`. + + - title: "`$__loc__`" + body: | + + Produces an object with a "file" key and a "line" key, with + the filename and line number where `$__loc__` occurs, as + values. + + examples: + - program: 'try error("\($__loc__)") catch .' + input: 'null' + output: ['"{\"file\":\"\",\"line\":1}"'] + + - title: "`paths`, `paths(node_filter)`" + body: | + + `paths` outputs the paths to all the elements in its input + (except it does not output the empty list, representing . + itself). + + `paths(f)` outputs the paths to any values for which `f` is `true`. + That is, `paths(type == "number")` outputs the paths to all numeric + values. + + examples: + - program: '[paths]' + input: '[1,[[],{"a":2}]]' + output: ['[[0],[1],[1,0],[1,1],[1,1,"a"]]'] + - program: '[paths(type == "number")]' + input: '[1,[[],{"a":2}]]' + output: ['[[0],[1,1,"a"]]'] + + - title: "`add`" + body: | + + The filter `add` takes as input an array, and produces as + output the elements of the array added together. This might + mean summed, concatenated or merged depending on the types + of the elements of the input array - the rules are the same + as those for the `+` operator (described above). + + If the input is an empty array, `add` returns `null`. + + examples: + - program: add + input: '["a","b","c"]' + output: ['"abc"'] + - program: add + input: '[1, 2, 3]' + output: ['6'] + - program: add + input: '[]' + output: ["null"] + + - title: "`any`, `any(condition)`, `any(generator; condition)`" + body: | + + The filter `any` takes as input an array of boolean values, + and produces `true` as output if any of the elements of + the array are `true`. + + If the input is an empty array, `any` returns `false`. + + The `any(condition)` form applies the given condition to the + elements of the input array. + + The `any(generator; condition)` form applies the given + condition to all the outputs of the given generator. + + examples: + - program: any + input: '[true, false]' + output: ["true"] + - program: any + input: '[false, false]' + output: ["false"] + - program: any + input: '[]' + output: ["false"] + + - title: "`all`, `all(condition)`, `all(generator; condition)`" + body: | + + The filter `all` takes as input an array of boolean values, + and produces `true` as output if all of the elements of + the array are `true`. + + The `all(condition)` form applies the given condition to the + elements of the input array. + + The `all(generator; condition)` form applies the given + condition to all the outputs of the given generator. + + If the input is an empty array, `all` returns `true`. + + examples: + - program: all + input: '[true, false]' + output: ["false"] + - program: all + input: '[true, true]' + output: ["true"] + - program: all + input: '[]' + output: ["true"] + + - title: "`flatten`, `flatten(depth)`" + body: | + + The filter `flatten` takes as input an array of nested arrays, + and produces a flat array in which all arrays inside the original + array have been recursively replaced by their values. You can pass + an argument to it to specify how many levels of nesting to flatten. + + `flatten(2)` is like `flatten`, but going only up to two + levels deep. + + examples: + - program: flatten + input: '[1, [2], [[3]]]' + output: ["[1, 2, 3]"] + - program: flatten(1) + input: '[1, [2], [[3]]]' + output: ["[1, 2, [3]]"] + - program: flatten + input: '[[]]' + output: ["[]"] + - program: flatten + input: '[{"foo": "bar"}, [{"foo": "baz"}]]' + output: ['[{"foo": "bar"}, {"foo": "baz"}]'] + + - title: "`range(upto)`, `range(from; upto)`, `range(from; upto; by)`" + body: | + + The `range` function produces a range of numbers. `range(4; 10)` + produces 6 numbers, from 4 (inclusive) to 10 (exclusive). The numbers + are produced as separate outputs. Use `[range(4; 10)]` to get a range as + an array. + + The one argument form generates numbers from 0 to the given + number, with an increment of 1. + + The two argument form generates numbers from `from` to `upto` + with an increment of 1. + + The three argument form generates numbers `from` to `upto` + with an increment of `by`. + + examples: + - program: 'range(2; 4)' + input: 'null' + output: ['2', '3'] + - program: '[range(2; 4)]' + input: 'null' + output: ['[2,3]'] + - program: '[range(4)]' + input: 'null' + output: ['[0,1,2,3]'] + - program: '[range(0; 10; 3)]' + input: 'null' + output: ['[0,3,6,9]'] + - program: '[range(0; 10; -1)]' + input: 'null' + output: ['[]'] + - program: '[range(0; -5; -1)]' + input: 'null' + output: ['[0,-1,-2,-3,-4]'] + + - title: "`floor`" + body: | + + The `floor` function returns the floor of its numeric input. + + examples: + - program: 'floor' + input: '3.14159' + output: ['3'] + + - title: "`sqrt`" + body: | + + The `sqrt` function returns the square root of its numeric input. + + examples: + - program: 'sqrt' + input: '9' + output: ['3'] + + - title: "`tonumber`" + body: | + + The `tonumber` function parses its input as a number. It + will convert correctly-formatted strings to their numeric + equivalent, leave numbers alone, and give an error on all other input. + + examples: + - program: '.[] | tonumber' + input: '[1, "1"]' + output: ['1', '1'] + + - title: "`tostring`" + body: | + + The `tostring` function prints its input as a + string. Strings are left unchanged, and all other values are + JSON-encoded. + + examples: + - program: '.[] | tostring' + input: '[1, "1", [1]]' + output: ['"1"', '"1"', '"[1]"'] + + - title: "`type`" + body: | + + The `type` function returns the type of its argument as a + string, which is one of null, boolean, number, string, array + or object. + + examples: + - program: 'map(type)' + input: '[0, false, [], {}, null, "hello"]' + output: ['["number", "boolean", "array", "object", "null", "string"]'] + + - title: "`infinite`, `nan`, `isinfinite`, `isnan`, `isfinite`, `isnormal`" + body: | + + Some arithmetic operations can yield infinities and "not a + number" (NaN) values. The `isinfinite` builtin returns `true` + if its input is infinite. The `isnan` builtin returns `true` + if its input is a NaN. The `infinite` builtin returns a + positive infinite value. The `nan` builtin returns a NaN. + The `isnormal` builtin returns true if its input is a normal + number. + + Note that division by zero raises an error. + + Currently most arithmetic operations operating on infinities, + NaNs, and sub-normals do not raise errors. + + examples: + - program: '.[] | (infinite * .) < 0' + input: '[-1, 1]' + output: ['true', 'false'] + - program: 'infinite, nan | type' + input: 'null' + output: ['"number"', '"number"'] + + - title: "`sort`, `sort_by(path_expression)`" + body: | + + The `sort` functions sorts its input, which must be an + array. Values are sorted in the following order: + + * `null` + * `false` + * `true` + * numbers + * strings, in alphabetical order (by unicode codepoint value) + * arrays, in lexical order + * objects + + The ordering for objects is a little complex: first they're + compared by comparing their sets of keys (as arrays in + sorted order), and if their keys are equal then the values + are compared key by key. + + `sort_by` may be used to sort by a particular field of an + object, or by applying any jq filter. `sort_by(f)` compares + two elements by comparing the result of `f` on each element. + When `f` produces multiple values, it firstly compares the + first values, and the second values if the first values are + equal, and so on. + + examples: + - program: 'sort' + input: '[8,3,null,6]' + output: ['[null,3,6,8]'] + + - program: 'sort_by(.foo)' + input: '[{"foo":4, "bar":10}, {"foo":3, "bar":10}, {"foo":2, "bar":1}]' + output: ['[{"foo":2, "bar":1}, {"foo":3, "bar":10}, {"foo":4, "bar":10}]'] + + - program: 'sort_by(.foo, .bar)' + input: '[{"foo":4, "bar":10}, {"foo":3, "bar":20}, {"foo":2, "bar":1}, {"foo":3, "bar":10}]' + output: ['[{"foo":2, "bar":1}, {"foo":3, "bar":10}, {"foo":3, "bar":20}, {"foo":4, "bar":10}]'] + + - title: "`group_by(path_expression)`" + body: | + + `group_by(.foo)` takes as input an array, groups the + elements having the same `.foo` field into separate arrays, + and produces all of these arrays as elements of a larger + array, sorted by the value of the `.foo` field. + + Any jq expression, not just a field access, may be used in + place of `.foo`. The sorting order is the same as described + in the `sort` function above. + + examples: + - program: 'group_by(.foo)' + input: '[{"foo":1, "bar":10}, {"foo":3, "bar":100}, {"foo":1, "bar":1}]' + output: ['[[{"foo":1, "bar":10}, {"foo":1, "bar":1}], [{"foo":3, "bar":100}]]'] + + - title: "`min`, `max`, `min_by(path_exp)`, `max_by(path_exp)`" + body: | + + Find the minimum or maximum element of the input array. + + The `min_by(path_exp)` and `max_by(path_exp)` functions allow + you to specify a particular field or property to examine, e.g. + `min_by(.foo)` finds the object with the smallest `foo` field. + + examples: + - program: 'min' + input: '[5,4,2,7]' + output: ['2'] + - program: 'max_by(.foo)' + input: '[{"foo":1, "bar":14}, {"foo":2, "bar":3}]' + output: ['{"foo":2, "bar":3}'] + + - title: "`unique`, `unique_by(path_exp)`" + body: | + + The `unique` function takes as input an array and produces + an array of the same elements, in sorted order, with + duplicates removed. + + The `unique_by(path_exp)` function will keep only one element + for each value obtained by applying the argument. Think of it + as making an array by taking one element out of every group + produced by `group`. + + examples: + - program: 'unique' + input: '[1,2,5,3,5,3,1,3]' + output: ['[1,2,3,5]'] + - program: 'unique_by(.foo)' + input: '[{"foo": 1, "bar": 2}, {"foo": 1, "bar": 3}, {"foo": 4, "bar": 5}]' + output: ['[{"foo": 1, "bar": 2}, {"foo": 4, "bar": 5}]'] + - program: 'unique_by(length)' + input: '["chunky", "bacon", "kitten", "cicada", "asparagus"]' + output: ['["bacon", "chunky", "asparagus"]'] + + - title: "`reverse`" + body: | + + This function reverses an array. + + examples: + - program: 'reverse' + input: '[1,2,3,4]' + output: ['[4,3,2,1]'] + + - title: "`contains(element)`" + body: | + + The filter `contains(b)` will produce true if b is + completely contained within the input. A string B is + contained in a string A if B is a substring of A. An array B + is contained in an array A if all elements in B are + contained in any element in A. An object B is contained in + object A if all of the values in B are contained in the + value in A with the same key. All other types are assumed to + be contained in each other if they are equal. + + examples: + - program: 'contains("bar")' + input: '"foobar"' + output: ['true'] + - program: 'contains(["baz", "bar"])' + input: '["foobar", "foobaz", "blarp"]' + output: ['true'] + - program: 'contains(["bazzzzz", "bar"])' + input: '["foobar", "foobaz", "blarp"]' + output: ['false'] + - program: 'contains({foo: 12, bar: [{barp: 12}]})' + input: '{"foo": 12, "bar":[1,2,{"barp":12, "blip":13}]}' + output: ['true'] + - program: 'contains({foo: 12, bar: [{barp: 15}]})' + input: '{"foo": 12, "bar":[1,2,{"barp":12, "blip":13}]}' + output: ['false'] + + - title: "`indices(s)`" + body: | + + Outputs an array containing the indices in `.` where `s` + occurs. The input may be an array, in which case if `s` is an + array then the indices output will be those where all elements + in `.` match those of `s`. + + examples: + - program: 'indices(", ")' + input: '"a,b, cd, efg, hijk"' + output: ['[3,7,12]'] + - program: 'indices(1)' + input: '[0,1,2,1,3,1,4]' + output: ['[1,3,5]'] + - program: 'indices([1,2])' + input: '[0,1,2,3,1,4,2,5,1,2,6,7]' + output: ['[1,8]'] + + - title: "`index(s)`, `rindex(s)`" + body: | + + Outputs the index of the first (`index`) or last (`rindex`) + occurrence of `s` in the input. + + examples: + - program: 'index(", ")' + input: '"a,b, cd, efg, hijk"' + output: ['3'] + - program: 'index(1)' + input: '[0,1,2,1,3,1,4]' + output: ['1'] + - program: 'index([1,2])' + input: '[0,1,2,3,1,4,2,5,1,2,6,7]' + output: ['1'] + - program: 'rindex(", ")' + input: '"a,b, cd, efg, hijk"' + output: ['12'] + - program: 'rindex(1)' + input: '[0,1,2,1,3,1,4]' + output: ['5'] + - program: 'rindex([1,2])' + input: '[0,1,2,3,1,4,2,5,1,2,6,7]' + output: ['8'] + + - title: "`inside`" + body: | + + The filter `inside(b)` will produce true if the input is + completely contained within b. It is, essentially, an + inversed version of `contains`. + + examples: + - program: 'inside("foobar")' + input: '"bar"' + output: ['true'] + - program: 'inside(["foobar", "foobaz", "blarp"])' + input: '["baz", "bar"]' + output: ['true'] + - program: 'inside(["foobar", "foobaz", "blarp"])' + input: '["bazzzzz", "bar"]' + output: ['false'] + - program: 'inside({"foo": 12, "bar":[1,2,{"barp":12, "blip":13}]})' + input: '{"foo": 12, "bar": [{"barp": 12}]}' + output: ['true'] + - program: 'inside({"foo": 12, "bar":[1,2,{"barp":12, "blip":13}]})' + input: '{"foo": 12, "bar": [{"barp": 15}]}' + output: ['false'] + + - title: "`startswith(str)`" + body: | + + Outputs `true` if . starts with the given string argument. + + examples: + - program: '[.[]|startswith("foo")]' + input: '["fo", "foo", "barfoo", "foobar", "barfoob"]' + output: ['[false, true, false, true, false]'] + + - title: "`endswith(str)`" + body: | + + Outputs `true` if . ends with the given string argument. + + examples: + - program: '[.[]|endswith("foo")]' + input: '["foobar", "barfoo"]' + output: ['[false, true]'] + + - title: "`combinations`, `combinations(n)`" + body: | + + Outputs all combinations of the elements of the arrays in the + input array. If given an argument `n`, it outputs all combinations + of `n` repetitions of the input array. + + examples: + - program: 'combinations' + input: '[[1,2], [3, 4]]' + output: ['[1, 3]', '[1, 4]', '[2, 3]', '[2, 4]'] + - program: 'combinations(2)' + input: '[0, 1]' + output: ['[0, 0]', '[0, 1]', '[1, 0]', '[1, 1]'] + + - title: "`ltrimstr(str)`" + body: | + + Outputs its input with the given prefix string removed, if it + starts with it. + + examples: + - program: '[.[]|ltrimstr("foo")]' + input: '["fo", "foo", "barfoo", "foobar", "afoo"]' + output: ['["fo","","barfoo","bar","afoo"]'] + + - title: "`rtrimstr(str)`" + body: | + + Outputs its input with the given suffix string removed, if it + ends with it. + + examples: + - program: '[.[]|rtrimstr("foo")]' + input: '["fo", "foo", "barfoo", "foobar", "foob"]' + output: ['["fo","","bar","foobar","foob"]'] + + - title: "`trim`, `ltrim`, `rtrim`" + body: | + + `trim` trims both leading and trailing whitespace. + + `ltrim` trims only leading (left side) whitespace. + + `rtrim` trims only trailing (right side) whitespace. + + Whitespace characters are the usual `" "`, `"\n"` `"\t"`, `"\r"` + and also all characters in the Unicode character database with the + whitespace property. Note that what considers whitespace might + change in the future. + + examples: + - program: 'trim, ltrim, rtrim' + input: '" abc "' + output: ['"abc"', '"abc "', '" abc"'] + + - title: "`explode`" + body: | + + Converts an input string into an array of the string's + codepoint numbers. + + examples: + - program: 'explode' + input: '"foobar"' + output: ['[102,111,111,98,97,114]'] + + - title: "`implode`" + body: | + + The inverse of explode. + + examples: + - program: 'implode' + input: '[65, 66, 67]' + output: ['"ABC"'] + + - title: "`split(str)`" + body: | + + Splits an input string on the separator argument. + + `split` can also split on regex matches when called with + two arguments (see the regular expressions section below). + + examples: + - program: 'split(", ")' + input: '"a, b,c,d, e, "' + output: ['["a","b,c,d","e",""]'] + + - title: "`join(str)`" + body: | + + Joins the array of elements given as input, using the + argument as separator. It is the inverse of `split`: that is, + running `split("foo") | join("foo")` over any input string + returns said input string. + + Numbers and booleans in the input are converted to strings. + Null values are treated as empty strings. Arrays and objects + in the input are not supported. + + examples: + - program: 'join(", ")' + input: '["a","b,c,d","e"]' + output: ['"a, b,c,d, e"'] + - program: 'join(" ")' + input: '["a",1,2.3,true,null,false]' + output: ['"a 1 2.3 true false"'] + + - title: "`ascii_downcase`, `ascii_upcase`" + body: | + + Emit a copy of the input string with its alphabetic characters (a-z and A-Z) + converted to the specified case. + + examples: + - program: 'ascii_upcase' + input: '"useful but not for é"' + output: ['"USEFUL BUT NOT FOR é"'] + + - title: "`while(cond; update)`" + body: | + + The `while(cond; update)` function allows you to repeatedly + apply an update to `.` until `cond` is false. + + Note that `while(cond; update)` is internally defined as a + recursive jq function. Recursive calls within `while` will + not consume additional memory if `update` produces at most one + output for each input. See advanced topics below. + + examples: + - program: '[while(.<100; .*2)]' + input: '1' + output: ['[1,2,4,8,16,32,64]'] + + - title: "`repeat(exp)`" + body: | + + The `repeat(exp)` function allows you to repeatedly + apply expression `exp` to `.` until an error is raised. + + Note that `repeat(exp)` is internally defined as a + recursive jq function. Recursive calls within `repeat` will + not consume additional memory if `exp` produces at most one + output for each input. See advanced topics below. + + examples: + - program: '[repeat(.*2, error)?]' + input: '1' + output: ['[2]'] + + - title: "`until(cond; next)`" + body: | + + The `until(cond; next)` function allows you to repeatedly + apply the expression `next`, initially to `.` then to its own + output, until `cond` is true. For example, this can be used + to implement a factorial function (see below). + + Note that `until(cond; next)` is internally defined as a + recursive jq function. Recursive calls within `until()` will + not consume additional memory if `next` produces at most one + output for each input. See advanced topics below. + + examples: + - program: '[.,1]|until(.[0] < 1; [.[0] - 1, .[1] * .[0]])|.[1]' + input: '4' + output: ['24'] + + + - title: "`recurse(f)`, `recurse`, `recurse(f; condition)`" + body: | + + The `recurse(f)` function allows you to search through a + recursive structure, and extract interesting data from all + levels. Suppose your input represents a filesystem: + + {"name": "/", "children": [ + {"name": "/bin", "children": [ + {"name": "/bin/ls", "children": []}, + {"name": "/bin/sh", "children": []}]}, + {"name": "/home", "children": [ + {"name": "/home/stephen", "children": [ + {"name": "/home/stephen/jq", "children": []}]}]}]} + + Now suppose you want to extract all of the filenames + present. You need to retrieve `.name`, `.children[].name`, + `.children[].children[].name`, and so on. You can do this + with: + + recurse(.children[]) | .name + + When called without an argument, `recurse` is equivalent to + `recurse(.[]?)`. + + `recurse(f)` is identical to `recurse(f; true)` and can be + used without concerns about recursion depth. + + `recurse(f; condition)` is a generator which begins by + emitting . and then emits in turn .|f, .|f|f, .|f|f|f, ... so long + as the computed value satisfies the condition. For example, + to generate all the integers, at least in principle, one + could write `recurse(.+1; true)`. + + The recursive calls in `recurse` will not consume additional + memory whenever `f` produces at most a single output for each + input. + + examples: + - program: 'recurse(.foo[])' + input: '{"foo":[{"foo": []}, {"foo":[{"foo":[]}]}]}' + output: + - '{"foo":[{"foo":[]},{"foo":[{"foo":[]}]}]}' + - '{"foo":[]}' + - '{"foo":[{"foo":[]}]}' + - '{"foo":[]}' + + - program: 'recurse' + input: '{"a":0,"b":[1]}' + output: + - '{"a":0,"b":[1]}' + - '0' + - '[1]' + - '1' + + - program: 'recurse(. * .; . < 20)' + input: '2' + output: ['2', '4', '16'] + + - title: "`walk(f)`" + body: | + + The `walk(f)` function applies f recursively to every + component of the input entity. When an array is + encountered, f is first applied to its elements and then to + the array itself; when an object is encountered, f is first + applied to all the values and then to the object. In + practice, f will usually test the type of its input, as + illustrated in the following examples. The first example + highlights the usefulness of processing the elements of an + array of arrays before processing the array itself. The second + example shows how all the keys of all the objects within the + input can be considered for alteration. + + examples: + - program: 'walk(if type == "array" then sort else . end)' + input: '[[4, 1, 7], [8, 5, 2], [3, 6, 9]]' + output: + - '[[1,4,7],[2,5,8],[3,6,9]]' + + - program: 'walk( if type == "object" then with_entries( .key |= sub( "^_+"; "") ) else . end )' + input: '[ { "_a": { "__b": 2 } } ]' + output: + - '[{"a":{"b":2}}]' + + - title: "`have_literal_numbers`" + body: | + + This builtin returns true if jq's build configuration + includes support for preservation of input number literals. + + - title: "`have_decnum`" + body: | + + This builtin returns true if jq was built with "decnum", + which is the current literal number preserving numeric + backend implementation for jq. + + - title: "`$JQ_BUILD_CONFIGURATION`" + body: | + + This builtin binding shows the jq executable's build + configuration. Its value has no particular format, but + it can be expected to be at least the `./configure` + command-line arguments, and may be enriched in the + future to include the version strings for the build + tooling used. + + Note that this can be overriden in the command-line + with `--arg` and related options. + + - title: "`$ENV`, `env`" + body: | + + `$ENV` is an object representing the environment variables as + set when the jq program started. + + `env` outputs an object representing jq's current environment. + + At the moment there is no builtin for setting environment + variables. + + examples: + - program: '$ENV.PAGER' + input: 'null' + output: ['"less"'] + + - program: 'env.PAGER' + input: 'null' + output: ['"less"'] + + - title: "`transpose`" + body: | + + Transpose a possibly jagged matrix (an array of arrays). + Rows are padded with nulls so the result is always rectangular. + + examples: + - program: 'transpose' + input: '[[1], [2,3]]' + output: ['[[1,2],[null,3]]'] + + - title: "`bsearch(x)`" + body: | + + `bsearch(x)` conducts a binary search for x in the input + array. If the input is sorted and contains x, then + `bsearch(x)` will return its index in the array; otherwise, if + the array is sorted, it will return (-1 - ix) where ix is an + insertion point such that the array would still be sorted + after the insertion of x at ix. If the array is not sorted, + `bsearch(x)` will return an integer that is probably of no + interest. + + examples: + - program: 'bsearch(0)' + input: '[0,1]' + output: ['0'] + - program: 'bsearch(0)' + input: '[1,2,3]' + output: ['-1'] + - program: 'bsearch(4) as $ix | if $ix < 0 then .[-(1+$ix)] = 4 else . end' + input: '[1,2,3]' + output: ['[1,2,3,4]'] + + - title: "String interpolation: `\\(exp)`" + body: | + + Inside a string, you can put an expression inside parens + after a backslash. Whatever the expression returns will be + interpolated into the string. + + examples: + - program: '"The input was \(.), which is one less than \(.+1)"' + input: '42' + output: ['"The input was 42, which is one less than 43"'] + + - title: "Convert to/from JSON" + body: | + + The `tojson` and `fromjson` builtins dump values as JSON texts + or parse JSON texts into values, respectively. The `tojson` + builtin differs from `tostring` in that `tostring` returns strings + unmodified, while `tojson` encodes strings as JSON strings. + + examples: + - program: '[.[]|tostring]' + input: '[1, "foo", ["foo"]]' + output: ['["1","foo","[\"foo\"]"]'] + - program: '[.[]|tojson]' + input: '[1, "foo", ["foo"]]' + output: ['["1","\"foo\"","[\"foo\"]"]'] + - program: '[.[]|tojson|fromjson]' + input: '[1, "foo", ["foo"]]' + output: ['[1,"foo",["foo"]]'] + + - title: "Format strings and escaping" + body: | + + The `@foo` syntax is used to format and escape strings, + which is useful for building URLs, documents in a language + like HTML or XML, and so forth. `@foo` can be used as a + filter on its own, the possible escapings are: + + * `@text`: + + Calls `tostring`, see that function for details. + + * `@json`: + + Serializes the input as JSON. + + * `@html`: + + Applies HTML/XML escaping, by mapping the characters + `<>&'"` to their entity equivalents `<`, `>`, + `&`, `'`, `"`. + + * `@uri`: + + Applies percent-encoding, by mapping all reserved URI + characters to a `%XX` sequence. + + * `@csv`: + + The input must be an array, and it is rendered as CSV + with double quotes for strings, and quotes escaped by + repetition. + + * `@tsv`: + + The input must be an array, and it is rendered as TSV + (tab-separated values). Each input array will be printed as + a single line. Fields are separated by a single + tab (ascii `0x09`). Input characters line-feed (ascii `0x0a`), + carriage-return (ascii `0x0d`), tab (ascii `0x09`) and + backslash (ascii `0x5c`) will be output as escape sequences + `\n`, `\r`, `\t`, `\\` respectively. + + * `@sh`: + + The input is escaped suitable for use in a command-line + for a POSIX shell. If the input is an array, the output + will be a series of space-separated strings. + + * `@base64`: + + The input is converted to base64 as specified by RFC 4648. + + * `@base64d`: + + The inverse of `@base64`, input is decoded as specified by RFC 4648. + Note\: If the decoded string is not UTF-8, the results are undefined. + + This syntax can be combined with string interpolation in a + useful way. You can follow a `@foo` token with a string + literal. The contents of the string literal will *not* be + escaped. However, all interpolations made inside that string + literal will be escaped. For instance, + + @uri "https://www.google.com/search?q=\(.search)" + + will produce the following output for the input + `{"search":"what is jq?"}`: + + "https://www.google.com/search?q=what%20is%20jq%3F" + + Note that the slashes, question mark, etc. in the URL are + not escaped, as they were part of the string literal. + + examples: + - program: '@html' + input: '"This works if x < y"' + output: ['"This works if x < y"'] + + - program: '@sh "echo \(.)"' + input: "\"O'Hara's Ale\"" + output: ["\"echo 'O'\\\\''Hara'\\\\''s Ale'\""] + + - program: '@base64' + input: '"This is a message"' + output: ['"VGhpcyBpcyBhIG1lc3NhZ2U="'] + + - program: '@base64d' + input: '"VGhpcyBpcyBhIG1lc3NhZ2U="' + output: ['"This is a message"'] + + - title: "Dates" + body: | + + jq provides some basic date handling functionality, with some + high-level and low-level builtins. In all cases these + builtins deal exclusively with time in UTC. + + The `fromdateiso8601` builtin parses datetimes in the ISO 8601 + format to a number of seconds since the Unix epoch + (1970-01-01T00:00:00Z). The `todateiso8601` builtin does the + inverse. + + The `fromdate` builtin parses datetime strings. Currently + `fromdate` only supports ISO 8601 datetime strings, but in the + future it will attempt to parse datetime strings in more + formats. + + The `todate` builtin is an alias for `todateiso8601`. + + The `now` builtin outputs the current time, in seconds since + the Unix epoch. + + Low-level jq interfaces to the C-library time functions are + also provided: `strptime`, `strftime`, `strflocaltime`, + `mktime`, `gmtime`, and `localtime`. Refer to your host + operating system's documentation for the format strings used + by `strptime` and `strftime`. Note: these are not necessarily + stable interfaces in jq, particularly as to their localization + functionality. + + The `gmtime` builtin consumes a number of seconds since the + Unix epoch and outputs a "broken down time" representation of + Greenwich Mean Time as an array of numbers representing + (in this order): the year, the month (zero-based), the day of + the month (one-based), the hour of the day, the minute of the + hour, the second of the minute, the day of the week, and the + day of the year -- all one-based unless otherwise stated. The + day of the week number may be wrong on some systems for dates + before March 1st 1900, or after December 31 2099. + + The `localtime` builtin works like the `gmtime` builtin, but + using the local timezone setting. + + The `mktime` builtin consumes "broken down time" + representations of time output by `gmtime` and `strptime`. + + The `strptime(fmt)` builtin parses input strings matching the + `fmt` argument. The output is in the "broken down time" + representation consumed by `gmtime` and output by `mktime`. + + The `strftime(fmt)` builtin formats a time (GMT) with the + given format. The `strflocaltime` does the same, but using + the local timezone setting. + + The format strings for `strptime` and `strftime` are described + in typical C library documentation. The format string for ISO + 8601 datetime is `"%Y-%m-%dT%H:%M:%SZ"`. + + jq may not support some or all of this date functionality on + some systems. In particular, the `%u` and `%j` specifiers for + `strptime(fmt)` are not supported on macOS. + + examples: + - program: 'fromdate' + input: '"2015-03-05T23:51:47Z"' + output: ['1425599507'] + + - program: 'strptime("%Y-%m-%dT%H:%M:%SZ")' + input: '"2015-03-05T23:51:47Z"' + output: ['[2015,2,5,23,51,47,4,63]'] + + - program: 'strptime("%Y-%m-%dT%H:%M:%SZ")|mktime' + input: '"2015-03-05T23:51:47Z"' + output: ['1425599507'] + + - title: "SQL-Style Operators" + body: | + + jq provides a few SQL-style operators. + + * INDEX(stream; index_expression): + + This builtin produces an object whose keys are computed by + the given index expression applied to each value from the + given stream. + + * JOIN($idx; stream; idx_expr; join_expr): + + This builtin joins the values from the given stream to the + given index. The index's keys are computed by applying the + given index expression to each value from the given stream. + An array of the value in the stream and the corresponding + value from the index is fed to the given join expression to + produce each result. + + * JOIN($idx; stream; idx_expr): + + Same as `JOIN($idx; stream; idx_expr; .)`. + + * JOIN($idx; idx_expr): + + This builtin joins the input `.` to the given index, applying + the given index expression to `.` to compute the index key. + The join operation is as described above. + + * IN(s): + + This builtin outputs `true` if `.` appears in the given + stream, otherwise it outputs `false`. + + * IN(source; s): + + This builtin outputs `true` if any value in the source stream + appears in the second stream, otherwise it outputs `false`. + + - title: "`builtins`" + body: | + + Returns a list of all builtin functions in the format `name/arity`. + Since functions with the same name but different arities are considered + separate functions, `all/0`, `all/1`, and `all/2` would all be present + in the list. + + - title: Conditionals and Comparisons + entries: + - title: "`==`, `!=`" + body: | + + The expression 'a == b' will produce 'true' if the results of evaluating + a and b are equal (that is, if they represent equivalent JSON values) and + 'false' otherwise. In particular, strings are never considered equal + to numbers. In checking for the equality of JSON objects, the ordering of keys + is irrelevant. If you're coming from JavaScript, please note that jq's `==` is like + JavaScript's `===`, the "strict equality" operator. + + != is "not equal", and 'a != b' returns the opposite value of 'a == b' + + examples: + - program: '. == false' + input: 'null' + output: ['false'] + + - program: '. == {"b": {"d": (4 + 1e-20), "c": 3}, "a":1}' + input: '{"a":1, "b": {"c": 3, "d": 4}}' + output: ['true'] + + - program: '.[] == 1' + input: '[1, 1.0, "1", "banana"]' + output: ['true', 'true', 'false', 'false'] + + - title: if-then-else-end + body: | + + `if A then B else C end` will act the same as `B` if `A` + produces a value other than false or null, but act the same + as `C` otherwise. + + `if A then B end` is the same as `if A then B else . end`. + That is, the `else` branch is optional, and if absent is the + same as `.`. This also applies to `elif` with absent ending `else` branch. + + Checking for false or null is a simpler notion of + "truthiness" than is found in JavaScript or Python, but it + means that you'll sometimes have to be more explicit about + the condition you want. You can't test whether, e.g. a + string is empty using `if .name then A else B end`; you'll + need something like `if .name == "" then A else B end` instead. + + If the condition `A` produces multiple results, then `B` is evaluated + once for each result that is not false or null, and `C` is evaluated + once for each false or null. + + More cases can be added to an if using `elif A then B` syntax. + + examples: + - program: |- + if . == 0 then + "zero" + elif . == 1 then + "one" + else + "many" + end + input: '2' + output: ['"many"'] + + - title: "`>`, `>=`, `<=`, `<`" + body: | + + The comparison operators `>`, `>=`, `<=`, `<` return whether + their left argument is greater than, greater than or equal + to, less than or equal to or less than their right argument + (respectively). + + The ordering is the same as that described for `sort`, above. + + examples: + - program: '. < 5' + input: '2' + output: ['true'] + + - title: "`and`, `or`, `not`" + body: | + + jq supports the normal Boolean operators `and`, `or`, `not`. + They have the same standard of truth as if expressions - + `false` and `null` are considered "false values", and + anything else is a "true value". + + If an operand of one of these operators produces multiple + results, the operator itself will produce a result for each input. + + `not` is in fact a builtin function rather than an operator, + so it is called as a filter to which things can be piped + rather than with special syntax, as in `.foo and .bar | + not`. + + These three only produce the values `true` and `false`, and + so are only useful for genuine Boolean operations, rather + than the common Perl/Python/Ruby idiom of + "value_that_may_be_null or default". If you want to use this + form of "or", picking between two values rather than + evaluating a condition, see the `//` operator below. + + examples: + - program: '42 and "a string"' + input: 'null' + output: ['true'] + - program: '(true, false) or false' + input: 'null' + output: ['true', 'false'] + - program: '(true, true) and (true, false)' + input: 'null' + output: ['true', 'false', 'true', 'false'] + - program: '[true, false | not]' + input: 'null' + output: ['[false, true]'] + + - title: "Alternative operator: `//`" + body: | + + The `//` operator produces all the values of its left-hand + side that are neither `false` nor `null`. If the + left-hand side produces no values other than `false` or + `null`, then `//` produces all the values of its right-hand + side. + + A filter of the form `a // b` produces all the results of + `a` that are not `false` or `null`. If `a` produces no + results, or no results other than `false` or `null`, then `a + // b` produces the results of `b`. + + This is useful for providing defaults: `.foo // 1` will + evaluate to `1` if there's no `.foo` element in the + input. It's similar to how `or` is sometimes used in Python + (jq's `or` operator is reserved for strictly Boolean + operations). + + Note: `some_generator // defaults_here` is not the same + as `some_generator | . // defaults_here`. The latter will + produce default values for all non-`false`, non-`null` + values of the left-hand side, while the former will not. + Precedence rules can make this confusing. For example, in + `false, 1 // 2` the left-hand side of `//` is `1`, not + `false, 1` -- `false, 1 // 2` parses the same way as `false, + (1 // 2)`. In `(false, null, 1) | . // 42` the left-hand + side of `//` is `.`, which always produces just one value, + while in `(false, null, 1) // 42` the left-hand side is a + generator of three values, and since it produces a + value other `false` and `null`, the default `42` is not + produced. + + examples: + - program: 'empty // 42' + input: 'null' + output: ['42'] + - program: '.foo // 42' + input: '{"foo": 19}' + output: ['19'] + - program: '.foo // 42' + input: '{}' + output: ['42'] + - program: '(false, null, 1) // 42' + input: 'null' + output: ['1'] + - program: '(false, null, 1) | . // 42' + input: 'null' + output: ['42', '42', '1'] + + - title: try-catch + body: | + + Errors can be caught by using `try EXP catch EXP`. The first + expression is executed, and if it fails then the second is + executed with the error message. The output of the handler, + if any, is output as if it had been the output of the + expression to try. + + The `try EXP` form uses `empty` as the exception handler. + + examples: + - program: 'try .a catch ". is not an object"' + input: 'true' + output: ['". is not an object"'] + - program: '[.[]|try .a]' + input: '[{}, true, {"a":1}]' + output: ['[null, 1]'] + - program: 'try error("some exception") catch .' + input: 'true' + output: ['"some exception"'] + + - title: Breaking out of control structures + body: | + + A convenient use of try/catch is to break out of control + structures like `reduce`, `foreach`, `while`, and so on. + + For example: + + # Repeat an expression until it raises "break" as an + # error, then stop repeating without re-raising the error. + # But if the error caught is not "break" then re-raise it. + try repeat(exp) catch if .=="break" then empty else error + + jq has a syntax for named lexical labels to "break" or "go (back) to": + + label $out | ... break $out ... + + The `break $label_name` expression will cause the program to + act as though the nearest (to the left) `label $label_name` + produced `empty`. + + The relationship between the `break` and corresponding `label` + is lexical: the label has to be "visible" from the break. + + To break out of a `reduce`, for example: + + label $out | reduce .[] as $item (null; if .==false then break $out else ... end) + + The following jq program produces a syntax error: + + break $out + + because no label `$out` is visible. + + - title: "Error Suppression / Optional Operator: `?`" + body: | + + The `?` operator, used as `EXP?`, is shorthand for `try EXP`. + + examples: + - program: '[.[] | .a?]' + input: '[{}, true, {"a":1}]' + output: ['[null, 1]'] + - program: '[.[] | tonumber?]' + input: '["1", "invalid", "3", 4]' + output: ['[1, 3, 4]'] + + - title: Regular expressions + body: | + + jq uses the + [Oniguruma regular expression library](https://github.com/kkos/oniguruma/blob/master/doc/RE), + as do PHP, TextMate, Sublime Text, etc, so the + description here will focus on jq specifics. + + Oniguruma supports several flavors of regular expression, so it is important to know + that jq uses the ["Perl NG" (Perl with named groups)](https://github.com/kkos/oniguruma/blob/master/doc/SYNTAX.md) flavor. + + The jq regex filters are defined so that they can be used using + one of these patterns: + + STRING | FILTER(REGEX) + STRING | FILTER(REGEX; FLAGS) + STRING | FILTER([REGEX]) + STRING | FILTER([REGEX, FLAGS]) + + where: + + * STRING, REGEX, and FLAGS are jq strings and subject to jq string interpolation; + * REGEX, after string interpolation, should be a valid regular expression; + * FILTER is one of `test`, `match`, or `capture`, as described below. + + Since REGEX must evaluate to a JSON string, some characters that are needed + to form a regular expression must be escaped. For example, the regular expression + `\s` signifying a whitespace character would be written as `"\\s"`. + + FLAGS is a string consisting of one of more of the supported flags: + + * `g` - Global search (find all matches, not just the first) + * `i` - Case insensitive search + * `m` - Multi line mode (`.` will match newlines) + * `n` - Ignore empty matches + * `p` - Both s and m modes are enabled + * `s` - Single line mode (`^` -> `\A`, `$` -> `\Z`) + * `l` - Find longest possible matches + * `x` - Extended regex format (ignore whitespace and comments) + + To match a whitespace with the `x` flag, use `\s`, e.g. + + jq -n '"a b" | test("a\\sb"; "x")' + + Note that certain flags may also be specified within REGEX, e.g. + + jq -n '("test", "TEst", "teST", "TEST") | test("(?i)te(?-i)st")' + + evaluates to: `true`, `true`, `false`, `false`. + + entries: + - title: "`test(val)`, `test(regex; flags)`" + body: | + + Like `match`, but does not return match objects, only `true` or `false` + for whether or not the regex matches the input. + + examples: + - program: 'test("foo")' + input: '"foo"' + output: ['true'] + - program: '.[] | test("a b c # spaces are ignored"; "ix")' + input: '["xabcd", "ABC"]' + output: ['true', 'true'] + + - title: "`match(val)`, `match(regex; flags)`" + body: | + + **match** outputs an object for each match it finds. Matches have + the following fields: + + * `offset` - offset in UTF-8 codepoints from the beginning of the input + * `length` - length in UTF-8 codepoints of the match + * `string` - the string that it matched + * `captures` - an array of objects representing capturing groups. + + Capturing group objects have the following fields: + + * `offset` - offset in UTF-8 codepoints from the beginning of the input + * `length` - length in UTF-8 codepoints of this capturing group + * `string` - the string that was captured + * `name` - the name of the capturing group (or `null` if it was unnamed) + + Capturing groups that did not match anything return an offset of -1 + + examples: + - program: 'match("(abc)+"; "g")' + input: '"abc abc"' + output: + - '{"offset": 0, "length": 3, "string": "abc", "captures": [{"offset": 0, "length": 3, "string": "abc", "name": null}]}' + - '{"offset": 4, "length": 3, "string": "abc", "captures": [{"offset": 4, "length": 3, "string": "abc", "name": null}]}' + - program: 'match("foo")' + input: '"foo bar foo"' + output: ['{"offset": 0, "length": 3, "string": "foo", "captures": []}'] + - program: 'match(["foo", "ig"])' + input: '"foo bar FOO"' + output: + - '{"offset": 0, "length": 3, "string": "foo", "captures": []}' + - '{"offset": 8, "length": 3, "string": "FOO", "captures": []}' + - program: 'match("foo (?bar)? foo"; "ig")' + input: '"foo bar foo foo foo"' + output: + - '{"offset": 0, "length": 11, "string": "foo bar foo", "captures": [{"offset": 4, "length": 3, "string": "bar", "name": "bar123"}]}' + - '{"offset": 12, "length": 8, "string": "foo foo", "captures": [{"offset": -1, "length": 0, "string": null, "name": "bar123"}]}' + + - program: '[ match("."; "g")] | length' + input: '"abc"' + output: ['3'] + + + - title: "`capture(val)`, `capture(regex; flags)`" + body: | + + Collects the named captures in a JSON object, with the name + of each capture as the key, and the matched string as the + corresponding value. + + examples: + - program: 'capture("(?[a-z]+)-(?[0-9]+)")' + input: '"xyzzy-14"' + output: ['{ "a": "xyzzy", "n": "14" }'] + + - title: "`scan(regex)`, `scan(regex; flags)`" + body: | + + Emit a stream of the non-overlapping substrings of the input + that match the regex in accordance with the flags, if any + have been specified. If there is no match, the stream is empty. + To capture all the matches for each input string, use the idiom + `[ expr ]`, e.g. `[ scan(regex) ]`. + + examples: + - program: 'scan("c")' + input: '"abcdefabc"' + output: ['"c"', '"c"'] + + - title: "`split(regex; flags)`" + body: | + + Splits an input string on each regex match. + + For backwards compatibility, when called with a single argument, + `split` splits on a string, not a regex. + + examples: + - program: 'split(", *"; null)' + input: '"ab,cd, ef"' + output: ['["ab","cd","ef"]'] + + + - title: "`splits(regex)`, `splits(regex; flags)`" + body: | + + These provide the same results as their `split` counterparts, + but as a stream instead of an array. + + examples: + - program: 'splits(", *")' + input: '"ab,cd, ef, gh"' + output: ['"ab"','"cd"','"ef"','"gh"'] + + - title: "`sub(regex; tostring)`, `sub(regex; tostring; flags)`" + body: | + + Emit the string obtained by replacing the first match of + regex in the input string with `tostring`, after + interpolation. `tostring` should be a jq string or a stream + of such strings, each of which may contain references to + named captures. The named captures are, in effect, presented + as a JSON object (as constructed by `capture`) to + `tostring`, so a reference to a captured variable named "x" + would take the form: `"\(.x)"`. + + examples: + - program: 'sub("[^a-z]*(?[a-z]+)"; "Z\(.x)"; "g")' + input: '"123abc456def"' + output: ['"ZabcZdef"'] + + - program: '[sub("(?.)"; "\(.a|ascii_upcase)", "\(.a|ascii_downcase)")]' + input: '"aB"' + output: ['["AB","aB"]'] + + - title: "`gsub(regex; tostring)`, `gsub(regex; tostring; flags)`" + body: | + + `gsub` is like `sub` but all the non-overlapping occurrences of the regex are + replaced by `tostring`, after interpolation. If the second argument is a stream + of jq strings, then `gsub` will produce a corresponding stream of JSON strings. + + examples: + - program: 'gsub("(?.)[^a]*"; "+\(.x)-")' + input: '"Abcabc"' + output: ['"+A-+a-"'] + + - program: '[gsub("p"; "a", "b")]' + input: '"p"' + output: ['["a","b"]'] + + + - title: Advanced features + body: | + Variables are an absolute necessity in most programming languages, but + they're relegated to an "advanced feature" in jq. + + In most languages, variables are the only means of passing around + data. If you calculate a value, and you want to use it more than once, + you'll need to store it in a variable. To pass a value to another part + of the program, you'll need that part of the program to define a + variable (as a function parameter, object member, or whatever) in + which to place the data. + + It is also possible to define functions in jq, although this is + is a feature whose biggest use is defining jq's standard library + (many jq functions such as `map` and `select` are in fact written + in jq). + + jq has reduction operators, which are very powerful but a bit + tricky. Again, these are mostly used internally, to define some + useful bits of jq's standard library. + + It may not be obvious at first, but jq is all about generators + (yes, as often found in other languages). Some utilities are + provided to help deal with generators. + + Some minimal I/O support (besides reading JSON from standard + input, and writing JSON to standard output) is available. + + Finally, there is a module/library system. + + entries: + - title: "Variable / Symbolic Binding Operator: `... as $identifier | ...`" + body: | + + In jq, all filters have an input and an output, so manual + plumbing is not necessary to pass a value from one part of a program + to the next. Many expressions, for instance `a + b`, pass their input + to two distinct subexpressions (here `a` and `b` are both passed the + same input), so variables aren't usually necessary in order to use a + value twice. + + For instance, calculating the average value of an array of numbers + requires a few variables in most languages - at least one to hold the + array, perhaps one for each element or for a loop counter. In jq, it's + simply `add / length` - the `add` expression is given the array and + produces its sum, and the `length` expression is given the array and + produces its length. + + So, there's generally a cleaner way to solve most problems in jq than + defining variables. Still, sometimes they do make things easier, so jq + lets you define variables using `expression as $variable`. All + variable names start with `$`. Here's a slightly uglier version of the + array-averaging example: + + length as $array_length | add / $array_length + + We'll need a more complicated problem to find a situation where using + variables actually makes our lives easier. + + + Suppose we have an array of blog posts, with "author" and "title" + fields, and another object which is used to map author usernames to + real names. Our input looks like: + + {"posts": [{"title": "First post", "author": "anon"}, + {"title": "A well-written article", "author": "person1"}], + "realnames": {"anon": "Anonymous Coward", + "person1": "Person McPherson"}} + + We want to produce the posts with the author field containing a real + name, as in: + + {"title": "First post", "author": "Anonymous Coward"} + {"title": "A well-written article", "author": "Person McPherson"} + + We use a variable, $names, to store the realnames object, so that we + can refer to it later when looking up author usernames: + + .realnames as $names | .posts[] | {title, author: $names[.author]} + + The expression `exp as $x | ...` means: for each value of expression + `exp`, run the rest of the pipeline with the entire original input, and + with `$x` set to that value. Thus `as` functions as something of a + foreach loop. + + Just as `{foo}` is a handy way of writing `{foo: .foo}`, so + `{$foo}` is a handy way of writing `{foo: $foo}`. + + Multiple variables may be declared using a single `as` expression by + providing a pattern that matches the structure of the input + (this is known as "destructuring"): + + . as {realnames: $names, posts: [$first, $second]} | ... + + The variable declarations in array patterns (e.g., `. as + [$first, $second]`) bind to the elements of the array in from + the element at index zero on up, in order. When there is no + value at the index for an array pattern element, `null` is + bound to that variable. + + Variables are scoped over the rest of the expression that defines + them, so + + .realnames as $names | (.posts[] | {title, author: $names[.author]}) + + will work, but + + (.realnames as $names | .posts[]) | {title, author: $names[.author]} + + won't. + + For programming language theorists, it's more accurate to + say that jq variables are lexically-scoped bindings. In + particular there's no way to change the value of a binding; + one can only setup a new binding with the same name, but which + will not be visible where the old one was. + + examples: + - program: '.bar as $x | .foo | . + $x' + input: '{"foo":10, "bar":200}' + output: ['210'] + - program: '. as $i|[(.*2|. as $i| $i), $i]' + input: '5' + output: ['[10,5]'] + - program: '. as [$a, $b, {c: $c}] | $a + $b + $c' + input: '[2, 3, {"c": 4, "d": 5}]' + output: ['9'] + - program: '.[] as [$a, $b] | {a: $a, b: $b}' + input: '[[0], [0, 1], [2, 1, 0]]' + output: ['{"a":0,"b":null}', '{"a":0,"b":1}', '{"a":2,"b":1}'] + + - title: 'Destructuring Alternative Operator: `?//`' + body: | + + The destructuring alternative operator provides a concise mechanism + for destructuring an input that can take one of several forms. + + Suppose we have an API that returns a list of resources and events + associated with them, and we want to get the user_id and timestamp of + the first event for each resource. The API (having been clumsily + converted from XML) will only wrap the events in an array if the resource + has multiple events: + + {"resources": [{"id": 1, "kind": "widget", "events": {"action": "create", "user_id": 1, "ts": 13}}, + {"id": 2, "kind": "widget", "events": [{"action": "create", "user_id": 1, "ts": 14}, {"action": "destroy", "user_id": 1, "ts": 15}]}]} + + We can use the destructuring alternative operator to handle this structural change simply: + + .resources[] as {$id, $kind, events: {$user_id, $ts}} ?// {$id, $kind, events: [{$user_id, $ts}]} | {$user_id, $kind, $id, $ts} + + Or, if we aren't sure if the input is an array of values or an object: + + .[] as [$id, $kind, $user_id, $ts] ?// {$id, $kind, $user_id, $ts} | ... + + Each alternative need not define all of the same variables, but all named + variables will be available to the subsequent expression. Variables not + matched in the alternative that succeeded will be `null`: + + .resources[] as {$id, $kind, events: {$user_id, $ts}} ?// {$id, $kind, events: [{$first_user_id, $first_ts}]} | {$user_id, $first_user_id, $kind, $id, $ts, $first_ts} + + Additionally, if the subsequent expression returns an error, the + alternative operator will attempt to try the next binding. Errors + that occur during the final alternative are passed through. + + [[3]] | .[] as [$a] ?// [$b] | if $a != null then error("err: \($a)") else {$a,$b} end + + examples: + - program: '.[] as {$a, $b, c: {$d, $e}} ?// {$a, $b, c: [{$d, $e}]} | {$a, $b, $d, $e}' + input: '[{"a": 1, "b": 2, "c": {"d": 3, "e": 4}}, {"a": 1, "b": 2, "c": [{"d": 3, "e": 4}]}]' + output: ['{"a":1,"b":2,"d":3,"e":4}', '{"a":1,"b":2,"d":3,"e":4}'] + - program: '.[] as {$a, $b, c: {$d}} ?// {$a, $b, c: [{$e}]} | {$a, $b, $d, $e}' + input: '[{"a": 1, "b": 2, "c": {"d": 3, "e": 4}}, {"a": 1, "b": 2, "c": [{"d": 3, "e": 4}]}]' + output: ['{"a":1,"b":2,"d":3,"e":null}', '{"a":1,"b":2,"d":null,"e":4}'] + - program: '.[] as [$a] ?// [$b] | if $a != null then error("err: \($a)") else {$a,$b} end' + input: '[[3]]' + output: ['{"a":null,"b":3}'] + + - title: 'Defining Functions' + body: | + + You can give a filter a name using "def" syntax: + + def increment: . + 1; + + From then on, `increment` is usable as a filter just like a + builtin function (in fact, this is how many of the builtins + are defined). A function may take arguments: + + def map(f): [.[] | f]; + + Arguments are passed as _filters_ (functions with no + arguments), _not_ as values. The same argument may be + referenced multiple times with different inputs (here `f` is + run for each element of the input array). Arguments to a + function work more like callbacks than like value arguments. + This is important to understand. Consider: + + def foo(f): f|f; + 5|foo(.*2) + + The result will be 20 because `f` is `.*2`, and during the + first invocation of `f` `.` will be 5, and the second time it + will be 10 (5 * 2), so the result will be 20. Function + arguments are filters, and filters expect an input when + invoked. + + If you want the value-argument behaviour for defining simple + functions, you can just use a variable: + + def addvalue(f): f as $f | map(. + $f); + + Or use the short-hand: + + def addvalue($f): ...; + + With either definition, `addvalue(.foo)` will add the current + input's `.foo` field to each element of the array. Do note + that calling `addvalue(.[])` will cause the `map(. + $f)` part + to be evaluated once per value in the value of `.` at the call + site. + + Multiple definitions using the same function name are allowed. + Each re-definition replaces the previous one for the same + number of function arguments, but only for references from + functions (or main program) subsequent to the re-definition. + See also the section below on scoping. + + examples: + - program: 'def addvalue(f): . + [f]; map(addvalue(.[0]))' + input: '[[1,2],[10,20]]' + output: ['[[1,2,1], [10,20,10]]'] + - program: 'def addvalue(f): f as $x | map(. + $x); addvalue(.[0])' + input: '[[1,2],[10,20]]' + output: ['[[1,2,1,2], [10,20,1,2]]'] + + - title: 'Scoping' + body: | + + There are two types of symbols in jq: value bindings (a.k.a., + "variables"), and functions. Both are scoped lexically, + with expressions being able to refer only to symbols that + have been defined "to the left" of them. The only exception + to this rule is that functions can refer to themselves so as + to be able to create recursive functions. + + For example, in the following expression there is a binding + which is visible "to the right" of it, `... | .*3 as + $times_three | [. + $times_three] | ...`, but not "to the + left". Consider this expression now, `... | (.*3 as + $times_three | [. + $times_three]) | ...`: here the binding + `$times_three` is _not_ visible past the closing parenthesis. + + - title: "`isempty(exp)`" + body: | + + Returns true if `exp` produces no outputs, false otherwise. + + examples: + - program: 'isempty(empty)' + input: 'null' + output: ['true'] + + - program: 'isempty(.[])' + input: '[]' + output: ['true'] + + - program: 'isempty(.[])' + input: '[1,2,3]' + output: ['false'] + + - title: "`limit(n; exp)`" + body: | + + The `limit` function extracts up to `n` outputs from `exp`. + + examples: + - program: '[limit(3;.[])]' + input: '[0,1,2,3,4,5,6,7,8,9]' + output: ['[0,1,2]'] + + - title: "`first(expr)`, `last(expr)`, `nth(n; expr)`" + body: | + + The `first(expr)` and `last(expr)` functions extract the first + and last values from `expr`, respectively. + + The `nth(n; expr)` function extracts the nth value output by `expr`. + Note that `nth(n; expr)` doesn't support negative values of `n`. + + examples: + - program: '[first(range(.)), last(range(.)), nth(./2; range(.))]' + input: '10' + output: ['[0,9,5]'] + + - title: "`first`, `last`, `nth(n)`" + body: | + + The `first` and `last` functions extract the first + and last values from any array at `.`. + + The `nth(n)` function extracts the nth value of any array at `.`. + + examples: + - program: '[range(.)]|[first, last, nth(5)]' + input: '10' + output: ['[0,9,5]'] + + - title: "`reduce`" + body: | + + The `reduce` syntax allows you to combine all of the results of + an expression by accumulating them into a single answer. + The form is `reduce EXP as $var (INIT; UPDATE)`. + As an example, we'll pass `[1,2,3]` to this expression: + + reduce .[] as $item (0; . + $item) + + For each result that `.[]` produces, `. + $item` is run to + accumulate a running total, starting from 0 as the input value. + In this example, `.[]` produces the results `1`, `2`, and `3`, + so the effect is similar to running something like this: + + 0 | 1 as $item | . + $item | + 2 as $item | . + $item | + 3 as $item | . + $item + + examples: + - program: 'reduce .[] as $item (0; . + $item)' + input: '[1,2,3,4,5]' + output: ['15'] + + - program: 'reduce .[] as [$i,$j] (0; . + $i * $j)' + input: '[[1,2],[3,4],[5,6]]' + output: ['44'] + + - program: 'reduce .[] as {$x,$y} (null; .x += $x | .y += [$y])' + input: '[{"x":"a","y":1},{"x":"b","y":2},{"x":"c","y":3}]' + output: ['{"x":"abc","y":[1,2,3]}'] + + - title: "`foreach`" + body: | + + The `foreach` syntax is similar to `reduce`, but intended to + allow the construction of `limit` and reducers that produce + intermediate results. + + The form is `foreach EXP as $var (INIT; UPDATE; EXTRACT)`. + As an example, we'll pass `[1,2,3]` to this expression: + + foreach .[] as $item (0; . + $item; [$item, . * 2]) + + Like the `reduce` syntax, `. + $item` is run for each result + that `.[]` produces, but `[$item, . * 2]` is run for each + intermediate values. In this example, since the intermediate + values are `1`, `3`, and `6`, the `foreach` expression produces + `[1,2]`, `[2,6]`, and `[3,12]`. So the effect is similar + to running something like this: + + 0 | 1 as $item | . + $item | [$item, . * 2], + 2 as $item | . + $item | [$item, . * 2], + 3 as $item | . + $item | [$item, . * 2] + + When `EXTRACT` is omitted, the identity filter is used. + That is, it outputs the intermediate values as they are. + + examples: + - program: 'foreach .[] as $item (0; . + $item)' + input: '[1,2,3,4,5]' + output: ['1','3','6','10','15'] + + - program: 'foreach .[] as $item (0; . + $item; [$item, . * 2])' + input: '[1,2,3,4,5]' + output: ['[1,2]','[2,6]','[3,12]','[4,20]','[5,30]'] + + - program: 'foreach .[] as $item (0; . + 1; {index: ., $item})' + input: '["foo", "bar", "baz"]' + output: + - '{"index":1,"item":"foo"}' + - '{"index":2,"item":"bar"}' + - '{"index":3,"item":"baz"}' + + - title: Recursion + body: | + + As described above, `recurse` uses recursion, and any jq + function can be recursive. The `while` builtin is also + implemented in terms of recursion. + + Tail calls are optimized whenever the expression to the left of + the recursive call outputs its last value. In practice this + means that the expression to the left of the recursive call + should not produce more than one output for each input. + + For example: + + def recurse(f): def r: ., (f | select(. != null) | r); r; + + def while(cond; update): + def _while: + if cond then ., (update | _while) else empty end; + _while; + + def repeat(exp): + def _repeat: + exp, _repeat; + _repeat; + + - title: Generators and iterators + body: | + + Some jq operators and functions are actually generators in + that they can produce zero, one, or more values for each + input, just as one might expect in other programming + languages that have generators. For example, `.[]` + generates all the values in its input (which must be an + array or an object), `range(0; 10)` generates the integers + between 0 and 10, and so on. + + Even the comma operator is a generator, generating first + the values generated by the expression to the left of the + comma, then the values generated by the expression on the + right of the comma. + + The `empty` builtin is the generator that produces zero + outputs. The `empty` builtin backtracks to the preceding + generator expression. + + All jq functions can be generators just by using builtin + generators. It is also possible to construct new generators + using only recursion and the comma operator. If + recursive calls are "in tail position" then the + generator will be efficient. In the example below the + recursive call by `_range` to itself is in tail position. + The example shows off three advanced topics: tail recursion, + generator construction, and sub-functions. + + examples: + - program: 'def range(init; upto; by): + def _range: + if (by > 0 and . < upto) or (by < 0 and . > upto) + then ., ((.+by)|_range) + else . end; + if by == 0 then init else init|_range end | + select((by > 0 and . < upto) or (by < 0 and . > upto)); + range(0; 10; 3)' + input: 'null' + output: ['0', '3', '6', '9'] + - program: 'def while(cond; update): + def _while: + if cond then ., (update | _while) else empty end; + _while; + [while(.<100; .*2)]' + input: '1' + output: ['[1,2,4,8,16,32,64]'] + + - title: 'Math' + body: | + + jq currently only has IEEE754 double-precision (64-bit) floating + point number support. + + Besides simple arithmetic operators such as `+`, jq also has most + standard math functions from the C math library. C math functions + that take a single input argument (e.g., `sin()`) are available as + zero-argument jq functions. C math functions that take two input + arguments (e.g., `pow()`) are available as two-argument jq + functions that ignore `.`. C math functions that take three input + arguments are available as three-argument jq functions that ignore + `.`. + + Availability of standard math functions depends on the + availability of the corresponding math functions in your operating + system and C math library. Unavailable math functions will be + defined but will raise an error. + + One-input C math functions: `acos` `acosh` `asin` `asinh` `atan` + `atanh` `cbrt` `ceil` `cos` `cosh` `erf` `erfc` `exp` `exp10` + `exp2` `expm1` `fabs` `floor` `gamma` `j0` `j1` `lgamma` `log` + `log10` `log1p` `log2` `logb` `nearbyint` `rint` `round` + `significand` `sin` `sinh` `sqrt` `tan` `tanh` `tgamma` `trunc` + `y0` `y1`. + + Two-input C math functions: `atan2` `copysign` `drem` `fdim` + `fmax` `fmin` `fmod` `frexp` `hypot` `jn` `ldexp` `modf` + `nextafter` `nexttoward` `pow` `remainder` `scalb` `scalbln` `yn`. + + Three-input C math functions: `fma`. + + See your system's manual for more information on each of these. + + - title: 'I/O' + body: | + + At this time jq has minimal support for I/O, mostly in the + form of control over when inputs are read. Two builtins functions + are provided for this, `input` and `inputs`, that read from the + same sources (e.g., `stdin`, files named on the command-line) as + jq itself. These two builtins, and jq's own reading actions, can + be interleaved with each other. They are commonly used in combination + with the null input option `-n` to prevent one input from being read + implicitly. + + Two builtins provide minimal output capabilities, `debug`, and + `stderr`. (Recall that a jq program's output values are always + output as JSON texts on `stdout`.) The `debug` builtin can have + application-specific behavior, such as for executables that use + the libjq C API but aren't the jq executable itself. The `stderr` + builtin outputs its input in raw mode to stder with no additional + decoration, not even a newline. + + Most jq builtins are referentially transparent, and yield constant + and repeatable value streams when applied to constant inputs. + This is not true of I/O builtins. + + entries: + - title: "`input`" + body: | + + Outputs one new input. + + Note that when using `input` it is generally be necessary to + invoke jq with the `-n` command-line option, otherwise + the first entity will be lost. + + echo 1 2 3 4 | jq '[., input]' # [1,2] [3,4] + + - title: "`inputs`" + body: | + + Outputs all remaining inputs, one by one. + + This is primarily useful for reductions over a program's + inputs. Note that when using `inputs` it is generally necessary + to invoke jq with the `-n` command-line option, otherwise + the first entity will be lost. + + echo 1 2 3 | jq -n 'reduce inputs as $i (0; . + $i)' # 6 + + - title: "`debug`, `debug(msgs)`" + body: | + + These two filters are like `.` but have as a side-effect the + production of one or more messages on stderr. + + The message produced by the `debug` filter has the form + + ["DEBUG:",] + + where `` is a compact rendition of the input + value. This format may change in the future. + + The `debug(msgs)` filter is defined as `(msgs | debug | empty), .` + thus allowing great flexibility in the content of the message, + while also allowing multi-line debugging statements to be created. + + For example, the expression: + + 1 as $x | 2 | debug("Entering function foo with $x == \($x)", .) | (.+1) + + would produce the value 3 but with the following two lines + being written to stderr: + + ["DEBUG:","Entering function foo with $x == 1"] + ["DEBUG:",2] + + - title: "`stderr`" + body: | + + Prints its input in raw and compact mode to stderr with no + additional decoration, not even a newline. + + - title: "`input_filename`" + body: | + + Returns the name of the file whose input is currently being + filtered. Note that this will not work well unless jq is + running in a UTF-8 locale. + + - title: "`input_line_number`" + body: | + + Returns the line number of the input currently being filtered. + + - title: 'Streaming' + body: | + + With the `--stream` option jq can parse input texts in a streaming + fashion, allowing jq programs to start processing large JSON texts + immediately rather than after the parse completes. If you have a + single JSON text that is 1GB in size, streaming it will allow you + to process it much more quickly. + + However, streaming isn't easy to deal with as the jq program will + have `[, ]` (and a few other forms) as inputs. + + Several builtins are provided to make handling streams easier. + + The examples below use the streamed form of `[0,[1]]`, which is + `[[0],0],[[1,0],1],[[1,0]],[[1]]`. + + Streaming forms include `[, ]` (to indicate any + scalar value, empty array, or empty object), and `[]` (to + indicate the end of an array or object). Future versions of jq + run with `--stream` and `--seq` may output additional forms such + as `["error message"]` when an input text fails to parse. + + entries: + - title: "`truncate_stream(stream_expression)`" + body: | + + Consumes a number as input and truncates the corresponding + number of path elements from the left of the outputs of the + given streaming expression. + + examples: + - program: 'truncate_stream([[0],1],[[1,0],2],[[1,0]],[[1]])' + input: '1' + output: ['[[0],2]', '[[0]]'] + + - title: "`fromstream(stream_expression)`" + body: | + + Outputs values corresponding to the stream expression's + outputs. + + examples: + - program: 'fromstream(1|truncate_stream([[0],1],[[1,0],2],[[1,0]],[[1]]))' + input: 'null' + output: ['[2]'] + + - title: "`tostream`" + body: | + + The `tostream` builtin outputs the streamed form of its input. + + examples: + - program: '. as $dot|fromstream($dot|tostream)|.==$dot' + input: '[0,[1,{"a":1},{"b":2}]]' + output: ['true'] + + - title: Assignment + body: | + Assignment works a little differently in jq than in most + programming languages. jq doesn't distinguish between references + to and copies of something - two objects or arrays are either + equal or not equal, without any further notion of being "the + same object" or "not the same object". + + If an object has two fields which are arrays, `.foo` and `.bar`, + and you append something to `.foo`, then `.bar` will not get + bigger, even if you've previously set `.bar = .foo`. If you're + used to programming in languages like Python, Java, Ruby, + JavaScript, etc. then you can think of it as though jq does a full + deep copy of every object before it does the assignment (for + performance it doesn't actually do that, but that's the general + idea). + + This means that it's impossible to build circular values in jq + (such as an array whose first element is itself). This is quite + intentional, and ensures that anything a jq program can produce + can be represented in JSON. + + All the assignment operators in jq have path expressions on the + left-hand side (LHS). The right-hand side (RHS) provides values + to set to the paths named by the LHS path expressions. + + Values in jq are always immutable. Internally, assignment works + by using a reduction to compute new, replacement values for `.` that + have had all the desired assignments applied to `.`, then + outputting the modified value. This might be made clear by this + example: `{a:{b:{c:1}}} | (.a.b|=3), .`. This will output + `{"a":{"b":3}}` and `{"a":{"b":{"c":1}}}` because the last + sub-expression, `.`, sees the original value, not the modified + value. + + Most users will want to use modification assignment operators, + such as `|=` or `+=`, rather than `=`. + + Note that the LHS of assignment operators refers to a value in + `.`. Thus `$var.foo = 1` won't work as expected (`$var.foo` is + not a valid or useful path expression in `.`); use `$var | .foo = + 1` instead. + + Note too that `.a,.b=0` does not set `.a` and `.b`, but + `(.a,.b)=0` sets both. + + entries: + - title: "Update-assignment: `|=`" + body: | + This is the "update" operator `|=`. It takes a filter on the + right-hand side and works out the new value for the property + of `.` being assigned to by running the old value through this + expression. For instance, `(.foo, .bar) |= .+1` will build an + object with the `foo` field set to the input's `foo` plus 1, + and the `bar` field set to the input's `bar` plus 1. + + The left-hand side can be any general path expression; see `path()`. + + Note that the left-hand side of `|=` refers to a value in `.`. + Thus `$var.foo |= . + 1` won't work as expected (`$var.foo` is + not a valid or useful path expression in `.`); use `$var | + .foo |= . + 1` instead. + + If the right-hand side outputs no values (i.e., `empty`), then + the left-hand side path will be deleted, as with `del(path)`. + + If the right-hand side outputs multiple values, only the first + one will be used (COMPATIBILITY NOTE: in jq 1.5 and earlier + releases, it used to be that only the last one was used). + + examples: + - program: '(..|select(type=="boolean")) |= if . then 1 else 0 end' + input: '[true,false,[5,true,[true,[false]],false]]' + output: ['[1,0,[5,1,[1,[0]],0]]'] + + - title: "Arithmetic update-assignment: `+=`, `-=`, `*=`, `/=`, `%=`, `//=`" + body: | + + jq has a few operators of the form `a op= b`, which are all + equivalent to `a |= . op b`. So, `+= 1` can be used to + increment values, being the same as `|= . + 1`. + + examples: + - program: .foo += 1 + input: '{"foo": 42}' + output: ['{"foo": 43}'] + + - title: "Plain assignment: `=`" + body: | + + This is the plain assignment operator. Unlike the others, the + input to the right-hand side (RHS) is the same as the input to + the left-hand side (LHS) rather than the value at the LHS + path, and all values output by the RHS will be used (as shown + below). + + If the RHS of `=` produces multiple values, then for each such + value jq will set the paths on the left-hand side to the value + and then it will output the modified `.`. For example, + `(.a,.b) = range(2)` outputs `{"a":0,"b":0}`, then + `{"a":1,"b":1}`. The "update" assignment forms (see above) do + not do this. + + This example should show the difference between `=` and `|=`: + + Provide input `{"a": {"b": 10}, "b": 20}` to the programs + + .a = .b + + and + + .a |= .b + + The former will set the `a` field of the input to the `b` + field of the input, and produce the output `{"a": 20, "b": 20}`. + The latter will set the `a` field of the input to the `a` + field's `b` field, producing `{"a": 10, "b": 20}`. + + examples: + - program: .a = .b + input: '{"a": {"b": 10}, "b": 20}' + output: ['{"a":20,"b":20}'] + + - program: .a |= .b + input: '{"a": {"b": 10}, "b": 20}' + output: ['{"a":10,"b":20}'] + + - program: (.a, .b) = range(3) + input: 'null' + output: + - '{"a":0,"b":0}' + - '{"a":1,"b":1}' + - '{"a":2,"b":2}' + + - program: (.a, .b) |= range(3) + input: 'null' + output: ['{"a":0,"b":0}'] + + - title: Complex assignments + body: | + Lots more things are allowed on the left-hand side of a jq assignment + than in most languages. We've already seen simple field accesses on + the left hand side, and it's no surprise that array accesses work just + as well: + + .posts[0].title = "JQ Manual" + + What may come as a surprise is that the expression on the left may + produce multiple results, referring to different points in the input + document: + + .posts[].comments |= . + ["this is great"] + + That example appends the string "this is great" to the "comments" + array of each post in the input (where the input is an object with a + field "posts" which is an array of posts). + + When jq encounters an assignment like 'a = b', it records the "path" + taken to select a part of the input document while executing a. This + path is then used to find which part of the input to change while + executing the assignment. Any filter may be used on the + left-hand side of an equals - whichever paths it selects from the + input will be where the assignment is performed. + + This is a very powerful operation. Suppose we wanted to add a comment + to blog posts, using the same "blog" input above. This time, we only + want to comment on the posts written by "stedolan". We can find those + posts using the "select" function described earlier: + + .posts[] | select(.author == "stedolan") + + The paths provided by this operation point to each of the posts that + "stedolan" wrote, and we can comment on each of them in the same way + that we did before: + + (.posts[] | select(.author == "stedolan") | .comments) |= + . + ["terrible."] + + - title: Comments + + body: | + + You can write comments in your jq filters using `#`. + + A `#` character (not part of a string) starts a comment. + All characters from `#` to the end of the line are ignored. + + If the end of the line is preceded by an odd number of backslash + characters, the following line is also considered part of the + comment and is ignored. + + For example, the following code outputs `[1,3,4,7]` + + [ + 1, + # foo \ + 2, + # bar \\ + 3, + 4, # baz \\\ + 5, \ + 6, + 7 + # comment \ + comment \ + comment + ] + + Backslash continuing the comment on the next line can be useful + when writing the "shebang" for a jq script: + + #!/bin/sh -- + # total - Output the sum of the given arguments (or stdin) + # usage: total [numbers...] + # \ + exec jq --args -MRnf "$0" -- "$@" + + $ARGS.positional | + reduce ( + if . == [] + then inputs + else .[] + end | + . as $dot | + try tonumber catch false | + if not or isnan then + @json "total: Invalid number \($dot).\n" | halt_error(1) + end + ) as $n (0; . + $n) + + The `exec` line is considered a comment by jq, so it is ignored. + But it is not ignored by `sh`, since in `sh` a backslash at the + end of the line does not continue the comment. + With this trick, when the script is invoked as `total 1 2`, + `/bin/sh -- /path/to/total 1 2` will be run, and `sh` will then + run `exec jq --args -MRnf /path/to/total -- 1 2` replacing itself + with a `jq` interpreter invoked with the specified options (`-M`, + `-R`, `-n`, `--args`), that evaluates the current file (`$0`), + with the arguments (`$@`) that were passed to `sh`. + + - title: Modules + body: | + + jq has a library/module system. Modules are files whose names end + in `.jq`. + + Modules imported by a program are searched for in a default search + path (see below). The `import` and `include` directives allow the + importer to alter this path. + + Paths in the search path are subject to various substitutions. + + For paths starting with `~/`, the user's home directory is + substituted for `~`. + + For paths starting with `$ORIGIN/`, the directory where the jq + executable is located is substituted for `$ORIGIN`. + + For paths starting with `./` or paths that are `.`, the path of + the including file is substituted for `.`. For top-level programs + given on the command-line, the current directory is used. + + Import directives can optionally specify a search path to which + the default is appended. + + The default search path is the search path given to the `-L` + command-line option, else `["~/.jq", "$ORIGIN/../lib/jq", + "$ORIGIN/../lib"]`. + + Null and empty string path elements terminate search path + processing. + + A dependency with relative path `foo/bar` would be searched for in + `foo/bar.jq` and `foo/bar/bar.jq` in the given search path. This + is intended to allow modules to be placed in a directory along + with, for example, version control files, README files, and so on, + but also to allow for single-file modules. + + Consecutive components with the same name are not allowed to avoid + ambiguities (e.g., `foo/foo`). + + For example, with `-L$HOME/.jq` a module `foo` can be found in + `$HOME/.jq/foo.jq` and `$HOME/.jq/foo/foo.jq`. + + If `$HOME/.jq` is a file, it is sourced into the main program. + + entries: + - title: "`import RelativePathString as NAME [];`" + body: | + + Imports a module found at the given path relative to a + directory in a search path. A `.jq` suffix will be added to + the relative path string. The module's symbols are prefixed + with `NAME::`. + + The optional metadata must be a constant jq expression. It + should be an object with keys like `homepage` and so on. At + this time jq only uses the `search` key/value of the metadata. + The metadata is also made available to users via the + `modulemeta` builtin. + + The `search` key in the metadata, if present, should have a + string or array value (array of strings); this is the search + path to be prefixed to the top-level search path. + + - title: "`include RelativePathString [];`" + body: | + + Imports a module found at the given path relative to a + directory in a search path as if it were included in place. A + `.jq` suffix will be added to the relative path string. The + module's symbols are imported into the caller's namespace as + if the module's content had been included directly. + + The optional metadata must be a constant jq expression. It + should be an object with keys like `homepage` and so on. At + this time jq only uses the `search` key/value of the metadata. + The metadata is also made available to users via the + `modulemeta` builtin. + + - title: "`import RelativePathString as $NAME [];`" + body: | + + Imports a JSON file found at the given path relative to a + directory in a search path. A `.json` suffix will be added to + the relative path string. The file's data will be available + as `$NAME::NAME`. + + The optional metadata must be a constant jq expression. It + should be an object with keys like `homepage` and so on. At + this time jq only uses the `search` key/value of the metadata. + The metadata is also made available to users via the + `modulemeta` builtin. + + The `search` key in the metadata, if present, should have a + string or array value (array of strings); this is the search + path to be prefixed to the top-level search path. + + - title: "`module ;`" + body: | + + This directive is entirely optional. It's not required for + proper operation. It serves only the purpose of providing + metadata that can be read with the `modulemeta` builtin. + + The metadata must be a constant jq expression. It should be + an object with keys like `homepage`. At this time jq doesn't + use this metadata, but it is made available to users via the + `modulemeta` builtin. + + - title: "`modulemeta`" + body: | + + Takes a module name as input and outputs the module's metadata + as an object, with the module's imports (including metadata) + as an array value for the `deps` key and the module's defined + functions as an array value for the `defs` key. + + Programs can use this to query a module's metadata, which they + could then use to, for example, search for, download, and + install missing dependencies. + + - title: Colors + body: | + + To configure alternative colors just set the `JQ_COLORS` + environment variable to colon-delimited list of partial terminal + escape sequences like `"1;31"`, in this order: + + - color for `null` + - color for `false` + - color for `true` + - color for numbers + - color for strings + - color for arrays + - color for objects + - color for object keys + + The default color scheme is the same as setting + `JQ_COLORS="0;90:0;39:0;39:0;39:0;32:1;39:1;39:1;34"`. + + This is not a manual for VT100/ANSI escapes. However, each of + these color specifications should consist of two numbers separated + by a semi-colon, where the first number is one of these: + + - 1 (bright) + - 2 (dim) + - 4 (underscore) + - 5 (blink) + - 7 (reverse) + - 8 (hidden) + + and the second is one of these: + + - 30 (black) + - 31 (red) + - 32 (green) + - 33 (yellow) + - 34 (blue) + - 35 (magenta) + - 36 (cyan) + - 37 (white) diff --git a/docs/content/manual/manual.yml b/docs/content/manual/manual.yml deleted file mode 100644 index d6746bc56a..0000000000 --- a/docs/content/manual/manual.yml +++ /dev/null @@ -1,3805 +0,0 @@ ---- -headline: jq Manual (development version) - -history: | - - *For released versions, see [jq 1.7](./v1.7/), [jq 1.6](./v1.6/), [jq 1.5](./v1.5/), - [jq 1.4](./v1.4/) or [jq 1.3](./v1.3/).* - -body: | - - A jq program is a "filter": it takes an input, and produces an - output. There are a lot of builtin filters for extracting a - particular field of an object, or converting a number to a string, - or various other standard tasks. - - Filters can be combined in various ways - you can pipe the output of - one filter into another filter, or collect the output of a filter - into an array. - - Some filters produce multiple results, for instance there's one that - produces all the elements of its input array. Piping that filter - into a second runs the second filter for each element of the - array. Generally, things that would be done with loops and iteration - in other languages are just done by gluing filters together in jq. - - It's important to remember that every filter has an input and an - output. Even literals like "hello" or 42 are filters - they take an - input but always produce the same literal as output. Operations that - combine two filters, like addition, generally feed the same input to - both and combine the results. So, you can implement an averaging - filter as `add / length` - feeding the input array both to the `add` - filter and the `length` filter and then performing the division. - - But that's getting ahead of ourselves. :) Let's start with something - simpler: - -manpage_intro: | - jq(1) -- Command-line JSON processor - ==================================== - - ## SYNOPSIS - - `jq` [...] [...] - - `jq` can transform JSON in various ways, by selecting, iterating, - reducing and otherwise mangling JSON documents. For instance, - running the command `jq 'map(.price) | add'` will take an array of - JSON objects as input and return the sum of their "price" fields. - - `jq` can accept text input as well, but by default, `jq` reads a - stream of JSON entities (including numbers and other literals) from - `stdin`. Whitespace is only needed to separate entities such as 1 - and 2, and true and false. One or more may be specified, in - which case `jq` will read input from those instead. - - The are described in the [INVOKING JQ] section; they - mostly concern input and output formatting. The is written - in the jq language and specifies how to transform the input - file or document. - - ## FILTERS - -manpage_epilogue: | - ## BUGS - - Presumably. Report them or discuss them at: - - https://github.com/jqlang/jq/issues - - ## AUTHOR - - Stephen Dolan `` - -sections: - - title: Invoking jq - body: | - - jq filters run on a stream of JSON data. The input to jq is - parsed as a sequence of whitespace-separated JSON values which - are passed through the provided filter one at a time. The - output(s) of the filter are written to standard output, as a - sequence of newline-separated JSON data. - - The simplest and most common filter (or jq program) is `.`, - which is the identity operator, copying the inputs of the jq - processor to the output stream. Because the default behavior of - the jq processor is to read JSON texts from the input stream, - and to pretty-print outputs, the `.` program's main use is to - validate and pretty-print the inputs. The jq programming - language is quite rich and allows for much more than just - validation and pretty-printing. - - Note: it is important to mind the shell's quoting rules. As a - general rule it's best to always quote (with single-quote - characters on Unix shells) the jq program, as too many characters with special - meaning to jq are also shell meta-characters. For example, `jq - "foo"` will fail on most Unix shells because that will be the same - as `jq foo`, which will generally fail because `foo is not - defined`. When using the Windows command shell (cmd.exe) it's - best to use double quotes around your jq program when given on the - command-line (instead of the `-f program-file` option), but then - double-quotes in the jq program need backslash escaping. When using - the Powershell (`powershell.exe`) or the Powershell Core - (`pwsh`/`pwsh.exe`), use single-quote characters around the jq - program and backslash-escaped double-quotes (`\"`) inside the jq - program. - - * Unix shells: `jq '.["foo"]'` - * Powershell: `jq '.[\"foo\"]'` - * Windows command shell: `jq ".[\"foo\"]"` - - Note: jq allows user-defined functions, but every jq program - must have a top-level expression. - - You can affect how jq reads and writes its input and output - using some command-line options: - - * `--null-input` / `-n`: - - Don't read any input at all. Instead, the filter is run once - using `null` as the input. This is useful when using jq as a - simple calculator or to construct JSON data from scratch. - - * `--raw-input` / `-R`: - - Don't parse the input as JSON. Instead, each line of text is - passed to the filter as a string. If combined with `--slurp`, - then the entire input is passed to the filter as a single long - string. - - * `--slurp` / `-s`: - - Instead of running the filter for each JSON object in the - input, read the entire input stream into a large array and run - the filter just once. - - * `--compact-output` / `-c`: - - By default, jq pretty-prints JSON output. Using this option - will result in more compact output by instead putting each - JSON object on a single line. - - * `--raw-output` / `-r`: - - With this option, if the filter's result is a string then it - will be written directly to standard output rather than being - formatted as a JSON string with quotes. This can be useful for - making jq filters talk to non-JSON-based systems. - - * `--raw-output0`: - - Like `-r` but jq will print NUL instead of newline after each output. - This can be useful when the values being output can contain newlines. - When the output value contains NUL, jq exits with non-zero code. - - * `--join-output` / `-j`: - - Like `-r` but jq won't print a newline after each output. - - * `--ascii-output` / `-a`: - - jq usually outputs non-ASCII Unicode codepoints as UTF-8, even - if the input specified them as escape sequences (like - "\u03bc"). Using this option, you can force jq to produce pure - ASCII output with every non-ASCII character replaced with the - equivalent escape sequence. - - * `--sort-keys` / `-S`: - - Output the fields of each object with the keys in sorted order. - - * `--color-output` / `-C` and `--monochrome-output` / `-M`: - - By default, jq outputs colored JSON if writing to a - terminal. You can force it to produce color even if writing to - a pipe or a file using `-C`, and disable color with `-M`. - When the `NO_COLOR` environment variable is not empty, jq disables - colored output by default, but you can enable it by `-C`. - - Colors can be configured with the `JQ_COLORS` environment - variable (see below). - - * `--tab`: - - Use a tab for each indentation level instead of two spaces. - - * `--indent n`: - - Use the given number of spaces (no more than 7) for indentation. - - * `--unbuffered`: - - Flush the output after each JSON object is printed (useful if - you're piping a slow data source into jq and piping jq's - output elsewhere). - - * `--stream`: - - Parse the input in streaming fashion, outputting arrays of path - and leaf values (scalars and empty arrays or empty objects). - For example, `"a"` becomes `[[],"a"]`, and `[[],"a",["b"]]` - becomes `[[0],[]]`, `[[1],"a"]`, and `[[2,0],"b"]`. - - This is useful for processing very large inputs. Use this in - conjunction with filtering and the `reduce` and `foreach` syntax - to reduce large inputs incrementally. - - * `--stream-errors`: - - Like `--stream`, but invalid JSON inputs yield array values - where the first element is the error and the second is a path. - For example, `["a",n]` produces `["Invalid literal at line 1, - column 7",[1]]`. - - Implies `--stream`. Invalid JSON inputs produce no error values - when `--stream` without `--stream-errors`. - - * `--seq`: - - Use the `application/json-seq` MIME type scheme for separating - JSON texts in jq's input and output. This means that an ASCII - RS (record separator) character is printed before each value on - output and an ASCII LF (line feed) is printed after every - output. Input JSON texts that fail to parse are ignored (but - warned about), discarding all subsequent input until the next - RS. This mode also parses the output of jq without the `--seq` - option. - - * `-f filename` / `--from-file filename`: - - Read filter from the file rather than from a command line, like - awk's -f option. - - * `-L directory`: - - Prepend `directory` to the search list for modules. If this - option is used then no builtin search list is used. See the - section on modules below. - - * `--arg name value`: - - This option passes a value to the jq program as a predefined - variable. If you run jq with `--arg foo bar`, then `$foo` is - available in the program and has the value `"bar"`. Note that - `value` will be treated as a string, so `--arg foo 123` will - bind `$foo` to `"123"`. - - Named arguments are also available to the jq program as - `$ARGS.named`. - - * `--argjson name JSON-text`: - - This option passes a JSON-encoded value to the jq program as a - predefined variable. If you run jq with `--argjson foo 123`, then - `$foo` is available in the program and has the value `123`. - - * `--slurpfile variable-name filename`: - - This option reads all the JSON texts in the named file and binds - an array of the parsed JSON values to the given global variable. - If you run jq with `--slurpfile foo bar`, then `$foo` is available - in the program and has an array whose elements correspond to the - texts in the file named `bar`. - - * `--rawfile variable-name filename`: - - This option reads in the named file and binds its contents to the given - global variable. If you run jq with `--rawfile foo bar`, then `$foo` is - available in the program and has a string whose contents are to the texts - in the file named `bar`. - - * `--args`: - - Remaining arguments are positional string arguments. These are - available to the jq program as `$ARGS.positional[]`. - - * `--jsonargs`: - - Remaining arguments are positional JSON text arguments. These - are available to the jq program as `$ARGS.positional[]`. - - * `--exit-status` / `-e`: - - Sets the exit status of jq to 0 if the last output value was - neither `false` nor `null`, 1 if the last output value was - either `false` or `null`, or 4 if no valid result was ever - produced. Normally jq exits with 2 if there was any usage - problem or system error, 3 if there was a jq program compile - error, or 0 if the jq program ran. - - Another way to set the exit status is with the `halt_error` - builtin function. - - * `--binary` / `-b`: - - Windows users using WSL, MSYS2, or Cygwin, should use this option - when using a native jq.exe, otherwise jq will turn newlines (LFs) - into carriage-return-then-newline (CRLF). - - * `--version` / `-V`: - - Output the jq version and exit with zero. - - * `--build-configuration`: - - Output the build configuration of jq and exit with zero. - This output has no supported format or structure and may change - without notice in future releases. - - * `--help` / `-h`: - - Output the jq help and exit with zero. - - * `--`: - - Terminates argument processing. Remaining arguments are not - interpreted as options. - - * `--run-tests [filename]`: - - Runs the tests in the given file or standard input. This must - be the last option given and does not honor all preceding - options. The input consists of comment lines, empty lines, and - program lines followed by one input line, as many lines of - output as are expected (one per output), and a terminating empty - line. Compilation failure tests start with a line containing - only `%%FAIL`, then a line containing the program to compile, - then a line containing an error message to compare to the - actual. - - Be warned that this option can change backwards-incompatibly. - - - title: Basic filters - entries: - - title: "Identity: `.`" - body: | - - The absolute simplest filter is `.` . This filter takes its - input and produces the same value as output. That is, this - is the identity operator. - - Since jq by default pretty-prints all output, a trivial - program consisting of nothing but `.` can be used to format - JSON output from, say, `curl`. - - Although the identity filter never modifies the value of its - input, jq processing can sometimes make it appear as though - it does. For example, using the current implementation of - jq, we would see that the expression: - - 1E1234567890 | . - - produces `1.7976931348623157e+308` on at least one platform. - This is because, in the process of parsing the number, this - particular version of jq has converted it to an IEEE754 - double-precision representation, losing precision. - - The way in which jq handles numbers has changed over time - and further changes are likely within the parameters set by - the relevant JSON standards. Moreover, build configuration - options can alter how jq processes numbers. - - The following remarks are therefore offered with the - understanding that they are intended to be descriptive of the - current version of jq and should not be interpreted as being - prescriptive: - - (1) Any arithmetic operation on a number that has not - already been converted to an IEEE754 double precision - representation will trigger a conversion to the IEEE754 - representation. - - (2) jq will attempt to maintain the original decimal - precision of number literals (if the `--disable-decnum` - build configuration option was not used), but in expressions - such `1E1234567890`, precision will be lost if the exponent - is too large. - - (3) In jq programs, a leading minus sign will trigger the - conversion of the number to an IEEE754 representation. - - (4) Comparisons are carried out using the untruncated - big decimal representation of numbers if available, as - illustrated in one of the following examples. - - The examples below use the builtin function `have_decnum` in - order to demonstrate the expected effects of using / not - using the `--disable-decnum` build configuration option, and - also to allow automated tests derived from these examples to - pass regardless of whether that option is used. - - examples: - - program: '.' - input: '"Hello, world!"' - output: ['"Hello, world!"'] - - - program: '.' - input: '0.12345678901234567890123456789' - output: ['0.12345678901234567890123456789'] - - - program: '[., tojson] | . == if have_decnum then [12345678909876543212345,"12345678909876543212345"] else [12345678909876543000000,"12345678909876543000000"] end' - input: '12345678909876543212345' - output: ['true'] - - - program: '. < 0.12345678901234567890123456788' - input: '0.12345678901234567890123456789' - output: ['false'] - - - program: 'map([., . == 1]) | tojson | . == if have_decnum then "[[1,true],[1.000,true],[1.0,true],[1.00,true]]" else "[[1,true],[1,true],[1,true],[1,true]]" end' - input: '[1, 1.000, 1.0, 100e-2]' - output: ['true'] - - - program: '. as $big | [$big, $big + 1] | map(. > 10000000000000000000000000000000) | . == if have_decnum then [true, false] else [false, false] end' - input: '10000000000000000000000000000001' - output: ['true'] - - - title: "Object Identifier-Index: `.foo`, `.foo.bar`" - body: | - - The simplest *useful* filter has the form `.foo`. When given a - JSON object (aka dictionary or hash) as input, `.foo` produces - the value at the key "foo" if the key is present, or null otherwise. - - A filter of the form `.foo.bar` is equivalent to `.foo | .bar`. - - The `.foo` syntax only works for simple, identifier-like keys, that - is, keys that are all made of alphanumeric characters and - underscore, and which do not start with a digit. - - If the key contains special characters or starts with a digit, - you need to surround it with double quotes like this: - `."foo$"`, or else `.["foo$"]`. - - For example `.["foo::bar"]` and `.["foo.bar"]` work while - `.foo::bar` does not. - - examples: - - program: '.foo' - input: '{"foo": 42, "bar": "less interesting data"}' - output: ['42'] - - - program: '.foo' - input: '{"notfoo": true, "alsonotfoo": false}' - output: ['null'] - - - program: '.["foo"]' - input: '{"foo": 42}' - output: ['42'] - - - title: "Optional Object Identifier-Index: `.foo?`" - body: | - - Just like `.foo`, but does not output an error when `.` is not an - object. - - examples: - - program: '.foo?' - input: '{"foo": 42, "bar": "less interesting data"}' - output: ['42'] - - program: '.foo?' - input: '{"notfoo": true, "alsonotfoo": false}' - output: ['null'] - - program: '.["foo"]?' - input: '{"foo": 42}' - output: ['42'] - - program: '[.foo?]' - input: '[1,2]' - output: ['[]'] - - - title: "Object Index: `.[]`" - body: | - - You can also look up fields of an object using syntax like - `.["foo"]` (`.foo` above is a shorthand version of this, but - only for identifier-like strings). - - - title: "Array Index: `.[]`" - body: | - - When the index value is an integer, `.[]` can index - arrays. Arrays are zero-based, so `.[2]` returns the third - element. - - Negative indices are allowed, with -1 referring to the last - element, -2 referring to the next to last element, and so on. - - examples: - - program: '.[0]' - input: '[{"name":"JSON", "good":true}, {"name":"XML", "good":false}]' - output: ['{"name":"JSON", "good":true}'] - - - program: '.[2]' - input: '[{"name":"JSON", "good":true}, {"name":"XML", "good":false}]' - output: ['null'] - - - program: '.[-2]' - input: '[1,2,3]' - output: ['2'] - - - title: "Array/String Slice: `.[:]`" - body: | - - The `.[:]` syntax can be used to return a - subarray of an array or substring of a string. The array - returned by `.[10:15]` will be of length 5, containing the - elements from index 10 (inclusive) to index 15 (exclusive). - Either index may be negative (in which case it counts - backwards from the end of the array), or omitted (in which - case it refers to the start or end of the array). - Indices are zero-based. - - examples: - - program: '.[2:4]' - input: '["a","b","c","d","e"]' - output: ['["c", "d"]'] - - - program: '.[2:4]' - input: '"abcdefghi"' - output: ['"cd"'] - - - program: '.[:3]' - input: '["a","b","c","d","e"]' - output: ['["a", "b", "c"]'] - - - program: '.[-2:]' - input: '["a","b","c","d","e"]' - output: ['["d", "e"]'] - - - title: "Array/Object Value Iterator: `.[]`" - body: | - - If you use the `.[index]` syntax, but omit the index - entirely, it will return *all* of the elements of an - array. Running `.[]` with the input `[1,2,3]` will produce the - numbers as three separate results, rather than as a single - array. A filter of the form `.foo[]` is equivalent to - `.foo | .[]`. - - You can also use this on an object, and it will return all - the values of the object. - - Note that the iterator operator is a generator of values. - - examples: - - program: '.[]' - input: '[{"name":"JSON", "good":true}, {"name":"XML", "good":false}]' - output: - - '{"name":"JSON", "good":true}' - - '{"name":"XML", "good":false}' - - - program: '.[]' - input: '[]' - output: [] - - - program: '.foo[]' - input: '{"foo":[1,2,3]}' - output: ['1','2','3'] - - - program: '.[]' - input: '{"a": 1, "b": 1}' - output: ['1', '1'] - - - title: "`.[]?`" - body: | - - Like `.[]`, but no errors will be output if . is not an array - or object. A filter of the form `.foo[]?` is equivalent to - `.foo | .[]?`. - - - title: "Comma: `,`" - body: | - - If two filters are separated by a comma, then the - same input will be fed into both and the two filters' output - value streams will be concatenated in order: first, all of the - outputs produced by the left expression, and then all of the - outputs produced by the right. For instance, filter `.foo, - .bar`, produces both the "foo" fields and "bar" fields as - separate outputs. - - The `,` operator is one way to construct generators. - - examples: - - program: '.foo, .bar' - input: '{"foo": 42, "bar": "something else", "baz": true}' - output: ['42', '"something else"'] - - - program: ".user, .projects[]" - input: '{"user":"stedolan", "projects": ["jq", "wikiflow"]}' - output: ['"stedolan"', '"jq"', '"wikiflow"'] - - - program: '.[4,2]' - input: '["a","b","c","d","e"]' - output: ['"e"', '"c"'] - - - title: "Pipe: `|`" - body: | - - The | operator combines two filters by feeding the output(s) of - the one on the left into the input of the one on the right. It's - similar to the Unix shell's pipe, if you're used to that. - - If the one on the left produces multiple results, the one on - the right will be run for each of those results. So, the - expression `.[] | .foo` retrieves the "foo" field of each - element of the input array. This is a cartesian product, - which can be surprising. - - Note that `.a.b.c` is the same as `.a | .b | .c`. - - Note too that `.` is the input value at the particular stage - in a "pipeline", specifically: where the `.` expression appears. - Thus `.a | . | .b` is the same as `.a.b`, as the `.` in the - middle refers to whatever value `.a` produced. - - examples: - - program: '.[] | .name' - input: '[{"name":"JSON", "good":true}, {"name":"XML", "good":false}]' - output: ['"JSON"', '"XML"'] - - - title: "Parenthesis" - body: | - - Parenthesis work as a grouping operator just as in any typical - programming language. - - examples: - - program: '(. + 2) * 5' - input: '1' - output: ['15'] - - - title: Types and Values - body: | - - jq supports the same set of datatypes as JSON - numbers, - strings, booleans, arrays, objects (which in JSON-speak are - hashes with only string keys), and "null". - - Booleans, null, strings and numbers are written the same way as - in JSON. Just like everything else in jq, these simple - values take an input and produce an output - `42` is a valid jq - expression that takes an input, ignores it, and returns 42 - instead. - - Numbers in jq are internally represented by their IEEE754 double - precision approximation. Any arithmetic operation with numbers, - whether they are literals or results of previous filters, will - produce a double precision floating point result. - - However, when parsing a literal jq will store the original literal - string. If no mutation is applied to this value then it will make - to the output in its original form, even if conversion to double - would result in a loss. - - entries: - - title: "Array construction: `[]`" - body: | - - As in JSON, `[]` is used to construct arrays, as in - `[1,2,3]`. The elements of the arrays can be any jq - expression, including a pipeline. All of the results produced - by all of the expressions are collected into one big array. - You can use it to construct an array out of a known quantity - of values (as in `[.foo, .bar, .baz]`) or to "collect" all the - results of a filter into an array (as in `[.items[].name]`) - - Once you understand the "," operator, you can look at jq's array - syntax in a different light: the expression `[1,2,3]` is not using a - built-in syntax for comma-separated arrays, but is instead applying - the `[]` operator (collect results) to the expression 1,2,3 (which - produces three different results). - - If you have a filter `X` that produces four results, - then the expression `[X]` will produce a single result, an - array of four elements. - - examples: - - program: "[.user, .projects[]]" - input: '{"user":"stedolan", "projects": ["jq", "wikiflow"]}' - output: ['["stedolan", "jq", "wikiflow"]'] - - program: "[ .[] | . * 2]" - input: '[1, 2, 3]' - output: ['[2, 4, 6]'] - - - title: "Object Construction: `{}`" - body: | - - Like JSON, `{}` is for constructing objects (aka - dictionaries or hashes), as in: `{"a": 42, "b": 17}`. - - If the keys are "identifier-like", then the quotes can be left - off, as in `{a:42, b:17}`. Variable references as key - expressions use the value of the variable as the key. Key - expressions other than constant literals, identifiers, or - variable references, need to be parenthesized, e.g., - `{("a"+"b"):59}`. - - The value can be any expression (although you may need to wrap - it in parentheses if, for example, it contains colons), which - gets applied to the {} expression's input (remember, all - filters have an input and an output). - - {foo: .bar} - - will produce the JSON object `{"foo": 42}` if given the JSON - object `{"bar":42, "baz":43}` as its input. You can use this - to select particular fields of an object: if the input is an - object with "user", "title", "id", and "content" fields and - you just want "user" and "title", you can write - - {user: .user, title: .title} - - Because that is so common, there's a shortcut syntax for it: - `{user, title}`. - - If one of the expressions produces multiple results, - multiple dictionaries will be produced. If the input's - - {"user":"stedolan","titles":["JQ Primer", "More JQ"]} - - then the expression - - {user, title: .titles[]} - - will produce two outputs: - - {"user":"stedolan", "title": "JQ Primer"} - {"user":"stedolan", "title": "More JQ"} - - Putting parentheses around the key means it will be evaluated as an - expression. With the same input as above, - - {(.user): .titles} - - produces - - {"stedolan": ["JQ Primer", "More JQ"]} - - Variable references as keys use the value of the variable as - the key. Without a value then the variable's name becomes the - key and its value becomes the value, - - "f o o" as $foo | "b a r" as $bar | {$foo, $bar:$foo} - - produces - - {"foo":"f o o","b a r":"f o o"} - - examples: - - program: '{user, title: .titles[]}' - input: '{"user":"stedolan","titles":["JQ Primer", "More JQ"]}' - output: - - '{"user":"stedolan", "title": "JQ Primer"}' - - '{"user":"stedolan", "title": "More JQ"}' - - program: '{(.user): .titles}' - input: '{"user":"stedolan","titles":["JQ Primer", "More JQ"]}' - output: ['{"stedolan": ["JQ Primer", "More JQ"]}'] - - - title: "Recursive Descent: `..`" - body: | - - Recursively descends `.`, producing every value. This is the - same as the zero-argument `recurse` builtin (see below). This - is intended to resemble the XPath `//` operator. Note that - `..a` does not work; use `.. | .a` instead. In the example - below we use `.. | .a?` to find all the values of object keys - "a" in any object found "below" `.`. - - This is particularly useful in conjunction with `path(EXP)` - (also see below) and the `?` operator. - - examples: - - program: '.. | .a?' - input: '[[{"a":1}]]' - output: ['1'] - - - title: Builtin operators and functions - body: | - - Some jq operators (for instance, `+`) do different things - depending on the type of their arguments (arrays, numbers, - etc.). However, jq never does implicit type conversions. If you - try to add a string to an object you'll get an error message and - no result. - - Please note that all numbers are converted to IEEE754 double precision - floating point representation. Arithmetic and logical operators are working - with these converted doubles. Results of all such operations are also limited - to the double precision. - - The only exception to this behaviour of number is a snapshot of original number - literal. When a number which originally was provided as a literal is never - mutated until the end of the program then it is printed to the output in its - original literal form. This also includes cases when the original literal - would be truncated when converted to the IEEE754 double precision floating point - number. - - entries: - - title: "Addition: `+`" - body: | - - The operator `+` takes two filters, applies them both - to the same input, and adds the results together. What - "adding" means depends on the types involved: - - - **Numbers** are added by normal arithmetic. - - - **Arrays** are added by being concatenated into a larger array. - - - **Strings** are added by being joined into a larger string. - - - **Objects** are added by merging, that is, inserting all - the key-value pairs from both objects into a single - combined object. If both objects contain a value for the - same key, the object on the right of the `+` wins. (For - recursive merge use the `*` operator.) - - `null` can be added to any value, and returns the other - value unchanged. - - examples: - - program: '.a + 1' - input: '{"a": 7}' - output: ['8'] - - program: '.a + .b' - input: '{"a": [1,2], "b": [3,4]}' - output: ['[1,2,3,4]'] - - program: '.a + null' - input: '{"a": 1}' - output: ['1'] - - program: '.a + 1' - input: '{}' - output: ['1'] - - program: '{a: 1} + {b: 2} + {c: 3} + {a: 42}' - input: 'null' - output: ['{"a": 42, "b": 2, "c": 3}'] - - - title: "Subtraction: `-`" - body: | - - As well as normal arithmetic subtraction on numbers, the `-` - operator can be used on arrays to remove all occurrences of - the second array's elements from the first array. - - examples: - - program: '4 - .a' - input: '{"a":3}' - output: ['1'] - - program: . - ["xml", "yaml"] - input: '["xml", "yaml", "json"]' - output: ['["json"]'] - - - title: "Multiplication, division, modulo: `*`, `/`, `%`" - body: | - - These infix operators behave as expected when given two numbers. - Division by zero raises an error. `x % y` computes x modulo y. - - Multiplying a string by a number produces the concatenation of - that string that many times. `"x" * 0` produces `""`. - - Dividing a string by another splits the first using the second - as separators. - - Multiplying two objects will merge them recursively: this works - like addition but if both objects contain a value for the - same key, and the values are objects, the two are merged with - the same strategy. - - examples: - - program: '10 / . * 3' - input: '5' - output: ['6'] - - program: '. / ", "' - input: '"a, b,c,d, e"' - output: ['["a","b,c,d","e"]'] - - program: '{"k": {"a": 1, "b": 2}} * {"k": {"a": 0,"c": 3}}' - input: 'null' - output: ['{"k": {"a": 0, "b": 2, "c": 3}}'] - - program: '.[] | (1 / .)?' - input: '[1,0,-1]' - output: ['1', '-1'] - - - title: "`abs`" - body: | - - The builtin function `abs` is defined naively as: `if . < 0 then - . else . end`. - - For numeric input, this is the absolute value. See the - section on the identity filter for the implications of this - definition for numeric input. - - To compute the absolute value of a number as a floating point number, you may wish use `fabs`. - - examples: - - program: 'map(abs)' - input: '[-10, -1.1, -1e-1]' - output: ['[10,1.1,1e-1]'] - - - title: "`length`" - body: | - - The builtin function `length` gets the length of various - different types of value: - - - The length of a **string** is the number of Unicode - codepoints it contains (which will be the same as its - JSON-encoded length in bytes if it's pure ASCII). - - - The length of a **number** is its absolute value. - - - The length of an **array** is the number of elements. - - - The length of an **object** is the number of key-value pairs. - - - The length of **null** is zero. - - - It is an error to use `length` on a **boolean**. - - examples: - - program: '.[] | length' - input: '[[1,2], "string", {"a":2}, null, -5]' - output: ['2', '6', '1', '0', '5'] - - - - title: "`utf8bytelength`" - body: | - - The builtin function `utf8bytelength` outputs the number of - bytes used to encode a string in UTF-8. - - examples: - - program: 'utf8bytelength' - input: '"\u03bc"' - output: ['2'] - - - title: "`keys`, `keys_unsorted`" - body: | - - The builtin function `keys`, when given an object, returns - its keys in an array. - - The keys are sorted "alphabetically", by unicode codepoint - order. This is not an order that makes particular sense in - any particular language, but you can count on it being the - same for any two objects with the same set of keys, - regardless of locale settings. - - When `keys` is given an array, it returns the valid indices - for that array: the integers from 0 to length-1. - - The `keys_unsorted` function is just like `keys`, but if - the input is an object then the keys will not be sorted, - instead the keys will roughly be in insertion order. - - examples: - - program: 'keys' - input: '{"abc": 1, "abcd": 2, "Foo": 3}' - output: ['["Foo", "abc", "abcd"]'] - - program: 'keys' - input: '[42,3,35]' - output: ['[0,1,2]'] - - - title: "`has(key)`" - body: | - - The builtin function `has` returns whether the input object - has the given key, or the input array has an element at the - given index. - - `has($key)` has the same effect as checking whether `$key` - is a member of the array returned by `keys`, although `has` - will be faster. - - examples: - - program: 'map(has("foo"))' - input: '[{"foo": 42}, {}]' - output: ['[true, false]'] - - program: 'map(has(2))' - input: '[[0,1], ["a","b","c"]]' - output: ['[false, true]'] - - - title: "`in`" - body: | - - The builtin function `in` returns whether or not the input key is in the - given object, or the input index corresponds to an element - in the given array. It is, essentially, an inversed version - of `has`. - - examples: - - program: '.[] | in({"foo": 42})' - input: '["foo", "bar"]' - output: ['true', 'false'] - - program: 'map(in([0,1]))' - input: '[2, 0]' - output: ['[false, true]'] - - - title: "`map(f)`, `map_values(f)`" - body: | - - For any filter `f`, `map(f)` and `map_values(f)` apply `f` - to each of the values in the input array or object, that is, - to the values of `.[]`. - - In the absence of errors, `map(f)` always outputs an array - whereas `map_values(f)` outputs an array if given an array, - or an object if given an object. - - When the input to `map_values(f)` is an object, the output - object has the same keys as the input object except for - those keys whose values when piped to `f` produce no values - at all. - - The key difference between `map(f)` and `map_values(f)` is - that the former simply forms an array from all the values of - `($x|f)` for each value, $x, in the input array or object, - but `map_values(f)` only uses `first($x|f)`. - - Specifically, for object inputs, `map_values(f)` constructs - the output object by examining in turn the value of - `first(.[$k]|f)` for each key, $k, of the input. If this - expression produces no values, then the corresponding key - will be dropped; otherwise, the output object will have that - value at the key, $k. - - Here are some examples to clarify the behavior of `map` and - `map_values` when applied to arrays. These examples assume the - input is `[1]` in all cases: - - map(.+1) #=> [2] - map(., .) #=> [1,1] - map(empty) #=> [] - - map_values(.+1) #=> [2] - map_values(., .) #=> [1] - map_values(empty) #=> [] - - `map(f)` is equivalent to `[.[] | f]` and - `map_values(f)` is equivalent to `.[] |= f`. - - In fact, these are their implementations. - - - examples: - - program: 'map(.+1)' - input: '[1,2,3]' - output: ['[2,3,4]'] - - - program: 'map_values(.+1)' - input: '{"a": 1, "b": 2, "c": 3}' - output: ['{"a": 2, "b": 3, "c": 4}'] - - - program: 'map(., .)' - input: '[1,2]' - output: ['[1,1,2,2]'] - - - program: 'map_values(. // empty)' - input: '{"a": null, "b": true, "c": false}' - output: ['{"b":true}'] - - - - title: "`pick(pathexps)`" - body: | - - Emit the projection of the input object or array defined by the - specified sequence of path expressions, such that if `p` is any - one of these specifications, then `(. | p)` will evaluate to the - same value as `(. | pick(pathexps) | p)`. For arrays, negative - indices and `.[m:n]` specifications should not be used. - - examples: - - program: 'pick(.a, .b.c, .x)' - input: '{"a": 1, "b": {"c": 2, "d": 3}, "e": 4}' - output: ['{"a":1,"b":{"c":2},"x":null}'] - - - program: 'pick(.[2], .[0], .[0])' - input: '[1,2,3,4]' - output: ['[1,null,3]'] - - - - title: "`path(path_expression)`" - body: | - - Outputs array representations of the given path expression - in `.`. The outputs are arrays of strings (object keys) - and/or numbers (array indices). - - Path expressions are jq expressions like `.a`, but also `.[]`. - There are two types of path expressions: ones that can match - exactly, and ones that cannot. For example, `.a.b.c` is an - exact match path expression, while `.a[].b` is not. - - `path(exact_path_expression)` will produce the array - representation of the path expression even if it does not - exist in `.`, if `.` is `null` or an array or an object. - - `path(pattern)` will produce array representations of the - paths matching `pattern` if the paths exist in `.`. - - Note that the path expressions are not different from normal - expressions. The expression - `path(..|select(type=="boolean"))` outputs all the paths to - boolean values in `.`, and only those paths. - - examples: - - program: 'path(.a[0].b)' - input: 'null' - output: ['["a",0,"b"]'] - - program: '[path(..)]' - input: '{"a":[{"b":1}]}' - output: ['[[],["a"],["a",0],["a",0,"b"]]'] - - - title: "`del(path_expression)`" - body: | - - The builtin function `del` removes a key and its corresponding - value from an object. - - examples: - - program: 'del(.foo)' - input: '{"foo": 42, "bar": 9001, "baz": 42}' - output: ['{"bar": 9001, "baz": 42}'] - - program: 'del(.[1, 2])' - input: '["foo", "bar", "baz"]' - output: ['["foo"]'] - - - title: "`getpath(PATHS)`" - body: | - - The builtin function `getpath` outputs the values in `.` found - at each path in `PATHS`. - - examples: - - program: 'getpath(["a","b"])' - input: 'null' - output: ['null'] - - program: '[getpath(["a","b"], ["a","c"])]' - input: '{"a":{"b":0, "c":1}}' - output: ['[0, 1]'] - - - title: "`setpath(PATHS; VALUE)`" - body: | - - The builtin function `setpath` sets the `PATHS` in `.` to `VALUE`. - - examples: - - program: 'setpath(["a","b"]; 1)' - input: 'null' - output: ['{"a": {"b": 1}}'] - - program: 'setpath(["a","b"]; 1)' - input: '{"a":{"b":0}}' - output: ['{"a": {"b": 1}}'] - - program: 'setpath([0,"a"]; 1)' - input: 'null' - output: ['[{"a":1}]'] - - - title: "`delpaths(PATHS)`" - body: | - - The builtin function `delpaths` deletes the `PATHS` in `.`. - `PATHS` must be an array of paths, where each path is an array - of strings and numbers. - - examples: - - program: 'delpaths([["a","b"]])' - input: '{"a":{"b":1},"x":{"y":2}}' - output: ['{"a":{},"x":{"y":2}}'] - - - title: "`to_entries`, `from_entries`, `with_entries(f)`" - body: | - - These functions convert between an object and an array of - key-value pairs. If `to_entries` is passed an object, then - for each `k: v` entry in the input, the output array - includes `{"key": k, "value": v}`. - - `from_entries` does the opposite conversion, and `with_entries(f)` - is a shorthand for `to_entries | map(f) | from_entries`, useful for - doing some operation to all keys and values of an object. - `from_entries` accepts `"key"`, `"Key"`, `"name"`, `"Name"`, - `"value"`, and `"Value"` as keys. - - examples: - - program: 'to_entries' - input: '{"a": 1, "b": 2}' - output: ['[{"key":"a", "value":1}, {"key":"b", "value":2}]'] - - program: 'from_entries' - input: '[{"key":"a", "value":1}, {"key":"b", "value":2}]' - output: ['{"a": 1, "b": 2}'] - - program: 'with_entries(.key |= "KEY_" + .)' - input: '{"a": 1, "b": 2}' - output: ['{"KEY_a": 1, "KEY_b": 2}'] - - - - title: "`select(boolean_expression)`" - body: | - - The function `select(f)` produces its input unchanged if - `f` returns true for that input, and produces no output - otherwise. - - It's useful for filtering lists: `[1,2,3] | map(select(. >= 2))` - will give you `[2,3]`. - - examples: - - program: 'map(select(. >= 2))' - input: '[1,5,3,0,7]' - output: ['[5,3,7]'] - - program: '.[] | select(.id == "second")' - input: '[{"id": "first", "val": 1}, {"id": "second", "val": 2}]' - output: ['{"id": "second", "val": 2}'] - - - - title: "`arrays`, `objects`, `iterables`, `booleans`, `numbers`, `normals`, `finites`, `strings`, `nulls`, `values`, `scalars`" - body: | - - These built-ins select only inputs that are arrays, objects, - iterables (arrays or objects), booleans, numbers, normal - numbers, finite numbers, strings, null, non-null values, and - non-iterables, respectively. - - examples: - - program: '.[]|numbers' - input: '[[],{},1,"foo",null,true,false]' - output: ['1'] - - - title: "`empty`" - body: | - - `empty` returns no results. None at all. Not even `null`. - - It's useful on occasion. You'll know if you need it :) - - examples: - - program: '1, empty, 2' - input: 'null' - output: ['1', '2'] - - program: '[1,2,empty,3]' - input: 'null' - output: ['[1,2,3]'] - - - title: "`error`, `error(message)`" - body: | - - Produces an error with the input value, or with the message - given as the argument. Errors can be caught with try/catch; - see below. - - examples: - - program: 'try error catch .' - input: '"error message"' - output: ['"error message"'] - - - program: 'try error("invalid value: \(.)") catch .' - input: '42' - output: ['"invalid value: 42"'] - - - title: "`halt`" - body: | - - Stops the jq program with no further outputs. jq will exit - with exit status `0`. - - - title: "`halt_error`, `halt_error(exit_code)`" - body: | - - Stops the jq program with no further outputs. The input will - be printed on `stderr` as raw output (i.e., strings will not - have double quotes) with no decoration, not even a newline. - - The given `exit_code` (defaulting to `5`) will be jq's exit - status. - - For example, `"Error: something went wrong\n"|halt_error(1)`. - - - title: "`$__loc__`" - body: | - - Produces an object with a "file" key and a "line" key, with - the filename and line number where `$__loc__` occurs, as - values. - - examples: - - program: 'try error("\($__loc__)") catch .' - input: 'null' - output: ['"{\"file\":\"\",\"line\":1}"'] - - - title: "`paths`, `paths(node_filter)`" - body: | - - `paths` outputs the paths to all the elements in its input - (except it does not output the empty list, representing . - itself). - - `paths(f)` outputs the paths to any values for which `f` is `true`. - That is, `paths(type == "number")` outputs the paths to all numeric - values. - - examples: - - program: '[paths]' - input: '[1,[[],{"a":2}]]' - output: ['[[0],[1],[1,0],[1,1],[1,1,"a"]]'] - - program: '[paths(type == "number")]' - input: '[1,[[],{"a":2}]]' - output: ['[[0],[1,1,"a"]]'] - - - title: "`add`" - body: | - - The filter `add` takes as input an array, and produces as - output the elements of the array added together. This might - mean summed, concatenated or merged depending on the types - of the elements of the input array - the rules are the same - as those for the `+` operator (described above). - - If the input is an empty array, `add` returns `null`. - - examples: - - program: add - input: '["a","b","c"]' - output: ['"abc"'] - - program: add - input: '[1, 2, 3]' - output: ['6'] - - program: add - input: '[]' - output: ["null"] - - - title: "`any`, `any(condition)`, `any(generator; condition)`" - body: | - - The filter `any` takes as input an array of boolean values, - and produces `true` as output if any of the elements of - the array are `true`. - - If the input is an empty array, `any` returns `false`. - - The `any(condition)` form applies the given condition to the - elements of the input array. - - The `any(generator; condition)` form applies the given - condition to all the outputs of the given generator. - - examples: - - program: any - input: '[true, false]' - output: ["true"] - - program: any - input: '[false, false]' - output: ["false"] - - program: any - input: '[]' - output: ["false"] - - - title: "`all`, `all(condition)`, `all(generator; condition)`" - body: | - - The filter `all` takes as input an array of boolean values, - and produces `true` as output if all of the elements of - the array are `true`. - - The `all(condition)` form applies the given condition to the - elements of the input array. - - The `all(generator; condition)` form applies the given - condition to all the outputs of the given generator. - - If the input is an empty array, `all` returns `true`. - - examples: - - program: all - input: '[true, false]' - output: ["false"] - - program: all - input: '[true, true]' - output: ["true"] - - program: all - input: '[]' - output: ["true"] - - - title: "`flatten`, `flatten(depth)`" - body: | - - The filter `flatten` takes as input an array of nested arrays, - and produces a flat array in which all arrays inside the original - array have been recursively replaced by their values. You can pass - an argument to it to specify how many levels of nesting to flatten. - - `flatten(2)` is like `flatten`, but going only up to two - levels deep. - - examples: - - program: flatten - input: '[1, [2], [[3]]]' - output: ["[1, 2, 3]"] - - program: flatten(1) - input: '[1, [2], [[3]]]' - output: ["[1, 2, [3]]"] - - program: flatten - input: '[[]]' - output: ["[]"] - - program: flatten - input: '[{"foo": "bar"}, [{"foo": "baz"}]]' - output: ['[{"foo": "bar"}, {"foo": "baz"}]'] - - - title: "`range(upto)`, `range(from; upto)`, `range(from; upto; by)`" - body: | - - The `range` function produces a range of numbers. `range(4; 10)` - produces 6 numbers, from 4 (inclusive) to 10 (exclusive). The numbers - are produced as separate outputs. Use `[range(4; 10)]` to get a range as - an array. - - The one argument form generates numbers from 0 to the given - number, with an increment of 1. - - The two argument form generates numbers from `from` to `upto` - with an increment of 1. - - The three argument form generates numbers `from` to `upto` - with an increment of `by`. - - examples: - - program: 'range(2; 4)' - input: 'null' - output: ['2', '3'] - - program: '[range(2; 4)]' - input: 'null' - output: ['[2,3]'] - - program: '[range(4)]' - input: 'null' - output: ['[0,1,2,3]'] - - program: '[range(0; 10; 3)]' - input: 'null' - output: ['[0,3,6,9]'] - - program: '[range(0; 10; -1)]' - input: 'null' - output: ['[]'] - - program: '[range(0; -5; -1)]' - input: 'null' - output: ['[0,-1,-2,-3,-4]'] - - - title: "`floor`" - body: | - - The `floor` function returns the floor of its numeric input. - - examples: - - program: 'floor' - input: '3.14159' - output: ['3'] - - - title: "`sqrt`" - body: | - - The `sqrt` function returns the square root of its numeric input. - - examples: - - program: 'sqrt' - input: '9' - output: ['3'] - - - title: "`tonumber`" - body: | - - The `tonumber` function parses its input as a number. It - will convert correctly-formatted strings to their numeric - equivalent, leave numbers alone, and give an error on all other input. - - examples: - - program: '.[] | tonumber' - input: '[1, "1"]' - output: ['1', '1'] - - - title: "`tostring`" - body: | - - The `tostring` function prints its input as a - string. Strings are left unchanged, and all other values are - JSON-encoded. - - examples: - - program: '.[] | tostring' - input: '[1, "1", [1]]' - output: ['"1"', '"1"', '"[1]"'] - - - title: "`type`" - body: | - - The `type` function returns the type of its argument as a - string, which is one of null, boolean, number, string, array - or object. - - examples: - - program: 'map(type)' - input: '[0, false, [], {}, null, "hello"]' - output: ['["number", "boolean", "array", "object", "null", "string"]'] - - - title: "`infinite`, `nan`, `isinfinite`, `isnan`, `isfinite`, `isnormal`" - body: | - - Some arithmetic operations can yield infinities and "not a - number" (NaN) values. The `isinfinite` builtin returns `true` - if its input is infinite. The `isnan` builtin returns `true` - if its input is a NaN. The `infinite` builtin returns a - positive infinite value. The `nan` builtin returns a NaN. - The `isnormal` builtin returns true if its input is a normal - number. - - Note that division by zero raises an error. - - Currently most arithmetic operations operating on infinities, - NaNs, and sub-normals do not raise errors. - - examples: - - program: '.[] | (infinite * .) < 0' - input: '[-1, 1]' - output: ['true', 'false'] - - program: 'infinite, nan | type' - input: 'null' - output: ['"number"', '"number"'] - - - title: "`sort`, `sort_by(path_expression)`" - body: | - - The `sort` functions sorts its input, which must be an - array. Values are sorted in the following order: - - * `null` - * `false` - * `true` - * numbers - * strings, in alphabetical order (by unicode codepoint value) - * arrays, in lexical order - * objects - - The ordering for objects is a little complex: first they're - compared by comparing their sets of keys (as arrays in - sorted order), and if their keys are equal then the values - are compared key by key. - - `sort_by` may be used to sort by a particular field of an - object, or by applying any jq filter. `sort_by(f)` compares - two elements by comparing the result of `f` on each element. - When `f` produces multiple values, it firstly compares the - first values, and the second values if the first values are - equal, and so on. - - examples: - - program: 'sort' - input: '[8,3,null,6]' - output: ['[null,3,6,8]'] - - - program: 'sort_by(.foo)' - input: '[{"foo":4, "bar":10}, {"foo":3, "bar":10}, {"foo":2, "bar":1}]' - output: ['[{"foo":2, "bar":1}, {"foo":3, "bar":10}, {"foo":4, "bar":10}]'] - - - program: 'sort_by(.foo, .bar)' - input: '[{"foo":4, "bar":10}, {"foo":3, "bar":20}, {"foo":2, "bar":1}, {"foo":3, "bar":10}]' - output: ['[{"foo":2, "bar":1}, {"foo":3, "bar":10}, {"foo":3, "bar":20}, {"foo":4, "bar":10}]'] - - - title: "`group_by(path_expression)`" - body: | - - `group_by(.foo)` takes as input an array, groups the - elements having the same `.foo` field into separate arrays, - and produces all of these arrays as elements of a larger - array, sorted by the value of the `.foo` field. - - Any jq expression, not just a field access, may be used in - place of `.foo`. The sorting order is the same as described - in the `sort` function above. - - examples: - - program: 'group_by(.foo)' - input: '[{"foo":1, "bar":10}, {"foo":3, "bar":100}, {"foo":1, "bar":1}]' - output: ['[[{"foo":1, "bar":10}, {"foo":1, "bar":1}], [{"foo":3, "bar":100}]]'] - - - title: "`min`, `max`, `min_by(path_exp)`, `max_by(path_exp)`" - body: | - - Find the minimum or maximum element of the input array. - - The `min_by(path_exp)` and `max_by(path_exp)` functions allow - you to specify a particular field or property to examine, e.g. - `min_by(.foo)` finds the object with the smallest `foo` field. - - examples: - - program: 'min' - input: '[5,4,2,7]' - output: ['2'] - - program: 'max_by(.foo)' - input: '[{"foo":1, "bar":14}, {"foo":2, "bar":3}]' - output: ['{"foo":2, "bar":3}'] - - - title: "`unique`, `unique_by(path_exp)`" - body: | - - The `unique` function takes as input an array and produces - an array of the same elements, in sorted order, with - duplicates removed. - - The `unique_by(path_exp)` function will keep only one element - for each value obtained by applying the argument. Think of it - as making an array by taking one element out of every group - produced by `group`. - - examples: - - program: 'unique' - input: '[1,2,5,3,5,3,1,3]' - output: ['[1,2,3,5]'] - - program: 'unique_by(.foo)' - input: '[{"foo": 1, "bar": 2}, {"foo": 1, "bar": 3}, {"foo": 4, "bar": 5}]' - output: ['[{"foo": 1, "bar": 2}, {"foo": 4, "bar": 5}]'] - - program: 'unique_by(length)' - input: '["chunky", "bacon", "kitten", "cicada", "asparagus"]' - output: ['["bacon", "chunky", "asparagus"]'] - - - title: "`reverse`" - body: | - - This function reverses an array. - - examples: - - program: 'reverse' - input: '[1,2,3,4]' - output: ['[4,3,2,1]'] - - - title: "`contains(element)`" - body: | - - The filter `contains(b)` will produce true if b is - completely contained within the input. A string B is - contained in a string A if B is a substring of A. An array B - is contained in an array A if all elements in B are - contained in any element in A. An object B is contained in - object A if all of the values in B are contained in the - value in A with the same key. All other types are assumed to - be contained in each other if they are equal. - - examples: - - program: 'contains("bar")' - input: '"foobar"' - output: ['true'] - - program: 'contains(["baz", "bar"])' - input: '["foobar", "foobaz", "blarp"]' - output: ['true'] - - program: 'contains(["bazzzzz", "bar"])' - input: '["foobar", "foobaz", "blarp"]' - output: ['false'] - - program: 'contains({foo: 12, bar: [{barp: 12}]})' - input: '{"foo": 12, "bar":[1,2,{"barp":12, "blip":13}]}' - output: ['true'] - - program: 'contains({foo: 12, bar: [{barp: 15}]})' - input: '{"foo": 12, "bar":[1,2,{"barp":12, "blip":13}]}' - output: ['false'] - - - title: "`indices(s)`" - body: | - - Outputs an array containing the indices in `.` where `s` - occurs. The input may be an array, in which case if `s` is an - array then the indices output will be those where all elements - in `.` match those of `s`. - - examples: - - program: 'indices(", ")' - input: '"a,b, cd, efg, hijk"' - output: ['[3,7,12]'] - - program: 'indices(1)' - input: '[0,1,2,1,3,1,4]' - output: ['[1,3,5]'] - - program: 'indices([1,2])' - input: '[0,1,2,3,1,4,2,5,1,2,6,7]' - output: ['[1,8]'] - - - title: "`index(s)`, `rindex(s)`" - body: | - - Outputs the index of the first (`index`) or last (`rindex`) - occurrence of `s` in the input. - - examples: - - program: 'index(", ")' - input: '"a,b, cd, efg, hijk"' - output: ['3'] - - program: 'index(1)' - input: '[0,1,2,1,3,1,4]' - output: ['1'] - - program: 'index([1,2])' - input: '[0,1,2,3,1,4,2,5,1,2,6,7]' - output: ['1'] - - program: 'rindex(", ")' - input: '"a,b, cd, efg, hijk"' - output: ['12'] - - program: 'rindex(1)' - input: '[0,1,2,1,3,1,4]' - output: ['5'] - - program: 'rindex([1,2])' - input: '[0,1,2,3,1,4,2,5,1,2,6,7]' - output: ['8'] - - - title: "`inside`" - body: | - - The filter `inside(b)` will produce true if the input is - completely contained within b. It is, essentially, an - inversed version of `contains`. - - examples: - - program: 'inside("foobar")' - input: '"bar"' - output: ['true'] - - program: 'inside(["foobar", "foobaz", "blarp"])' - input: '["baz", "bar"]' - output: ['true'] - - program: 'inside(["foobar", "foobaz", "blarp"])' - input: '["bazzzzz", "bar"]' - output: ['false'] - - program: 'inside({"foo": 12, "bar":[1,2,{"barp":12, "blip":13}]})' - input: '{"foo": 12, "bar": [{"barp": 12}]}' - output: ['true'] - - program: 'inside({"foo": 12, "bar":[1,2,{"barp":12, "blip":13}]})' - input: '{"foo": 12, "bar": [{"barp": 15}]}' - output: ['false'] - - - title: "`startswith(str)`" - body: | - - Outputs `true` if . starts with the given string argument. - - examples: - - program: '[.[]|startswith("foo")]' - input: '["fo", "foo", "barfoo", "foobar", "barfoob"]' - output: ['[false, true, false, true, false]'] - - - title: "`endswith(str)`" - body: | - - Outputs `true` if . ends with the given string argument. - - examples: - - program: '[.[]|endswith("foo")]' - input: '["foobar", "barfoo"]' - output: ['[false, true]'] - - - title: "`combinations`, `combinations(n)`" - body: | - - Outputs all combinations of the elements of the arrays in the - input array. If given an argument `n`, it outputs all combinations - of `n` repetitions of the input array. - - examples: - - program: 'combinations' - input: '[[1,2], [3, 4]]' - output: ['[1, 3]', '[1, 4]', '[2, 3]', '[2, 4]'] - - program: 'combinations(2)' - input: '[0, 1]' - output: ['[0, 0]', '[0, 1]', '[1, 0]', '[1, 1]'] - - - title: "`ltrimstr(str)`" - body: | - - Outputs its input with the given prefix string removed, if it - starts with it. - - examples: - - program: '[.[]|ltrimstr("foo")]' - input: '["fo", "foo", "barfoo", "foobar", "afoo"]' - output: ['["fo","","barfoo","bar","afoo"]'] - - - title: "`rtrimstr(str)`" - body: | - - Outputs its input with the given suffix string removed, if it - ends with it. - - examples: - - program: '[.[]|rtrimstr("foo")]' - input: '["fo", "foo", "barfoo", "foobar", "foob"]' - output: ['["fo","","bar","foobar","foob"]'] - - - title: "`trim`, `ltrim`, `rtrim`" - body: | - - `trim` trims both leading and trailing whitespace. - - `ltrim` trims only leading (left side) whitespace. - - `rtrim` trims only trailing (right side) whitespace. - - Whitespace characters are the usual `" "`, `"\n"` `"\t"`, `"\r"` - and also all characters in the Unicode character database with the - whitespace property. Note that what considers whitespace might - change in the future. - - examples: - - program: 'trim, ltrim, rtrim' - input: '" abc "' - output: ['"abc"', '"abc "', '" abc"'] - - - title: "`explode`" - body: | - - Converts an input string into an array of the string's - codepoint numbers. - - examples: - - program: 'explode' - input: '"foobar"' - output: ['[102,111,111,98,97,114]'] - - - title: "`implode`" - body: | - - The inverse of explode. - - examples: - - program: 'implode' - input: '[65, 66, 67]' - output: ['"ABC"'] - - - title: "`split(str)`" - body: | - - Splits an input string on the separator argument. - - `split` can also split on regex matches when called with - two arguments (see the regular expressions section below). - - examples: - - program: 'split(", ")' - input: '"a, b,c,d, e, "' - output: ['["a","b,c,d","e",""]'] - - - title: "`join(str)`" - body: | - - Joins the array of elements given as input, using the - argument as separator. It is the inverse of `split`: that is, - running `split("foo") | join("foo")` over any input string - returns said input string. - - Numbers and booleans in the input are converted to strings. - Null values are treated as empty strings. Arrays and objects - in the input are not supported. - - examples: - - program: 'join(", ")' - input: '["a","b,c,d","e"]' - output: ['"a, b,c,d, e"'] - - program: 'join(" ")' - input: '["a",1,2.3,true,null,false]' - output: ['"a 1 2.3 true false"'] - - - title: "`ascii_downcase`, `ascii_upcase`" - body: | - - Emit a copy of the input string with its alphabetic characters (a-z and A-Z) - converted to the specified case. - - examples: - - program: 'ascii_upcase' - input: '"useful but not for é"' - output: ['"USEFUL BUT NOT FOR é"'] - - - title: "`while(cond; update)`" - body: | - - The `while(cond; update)` function allows you to repeatedly - apply an update to `.` until `cond` is false. - - Note that `while(cond; update)` is internally defined as a - recursive jq function. Recursive calls within `while` will - not consume additional memory if `update` produces at most one - output for each input. See advanced topics below. - - examples: - - program: '[while(.<100; .*2)]' - input: '1' - output: ['[1,2,4,8,16,32,64]'] - - - title: "`repeat(exp)`" - body: | - - The `repeat(exp)` function allows you to repeatedly - apply expression `exp` to `.` until an error is raised. - - Note that `repeat(exp)` is internally defined as a - recursive jq function. Recursive calls within `repeat` will - not consume additional memory if `exp` produces at most one - output for each input. See advanced topics below. - - examples: - - program: '[repeat(.*2, error)?]' - input: '1' - output: ['[2]'] - - - title: "`until(cond; next)`" - body: | - - The `until(cond; next)` function allows you to repeatedly - apply the expression `next`, initially to `.` then to its own - output, until `cond` is true. For example, this can be used - to implement a factorial function (see below). - - Note that `until(cond; next)` is internally defined as a - recursive jq function. Recursive calls within `until()` will - not consume additional memory if `next` produces at most one - output for each input. See advanced topics below. - - examples: - - program: '[.,1]|until(.[0] < 1; [.[0] - 1, .[1] * .[0]])|.[1]' - input: '4' - output: ['24'] - - - - title: "`recurse(f)`, `recurse`, `recurse(f; condition)`" - body: | - - The `recurse(f)` function allows you to search through a - recursive structure, and extract interesting data from all - levels. Suppose your input represents a filesystem: - - {"name": "/", "children": [ - {"name": "/bin", "children": [ - {"name": "/bin/ls", "children": []}, - {"name": "/bin/sh", "children": []}]}, - {"name": "/home", "children": [ - {"name": "/home/stephen", "children": [ - {"name": "/home/stephen/jq", "children": []}]}]}]} - - Now suppose you want to extract all of the filenames - present. You need to retrieve `.name`, `.children[].name`, - `.children[].children[].name`, and so on. You can do this - with: - - recurse(.children[]) | .name - - When called without an argument, `recurse` is equivalent to - `recurse(.[]?)`. - - `recurse(f)` is identical to `recurse(f; true)` and can be - used without concerns about recursion depth. - - `recurse(f; condition)` is a generator which begins by - emitting . and then emits in turn .|f, .|f|f, .|f|f|f, ... so long - as the computed value satisfies the condition. For example, - to generate all the integers, at least in principle, one - could write `recurse(.+1; true)`. - - The recursive calls in `recurse` will not consume additional - memory whenever `f` produces at most a single output for each - input. - - examples: - - program: 'recurse(.foo[])' - input: '{"foo":[{"foo": []}, {"foo":[{"foo":[]}]}]}' - output: - - '{"foo":[{"foo":[]},{"foo":[{"foo":[]}]}]}' - - '{"foo":[]}' - - '{"foo":[{"foo":[]}]}' - - '{"foo":[]}' - - - program: 'recurse' - input: '{"a":0,"b":[1]}' - output: - - '{"a":0,"b":[1]}' - - '0' - - '[1]' - - '1' - - - program: 'recurse(. * .; . < 20)' - input: '2' - output: ['2', '4', '16'] - - - title: "`walk(f)`" - body: | - - The `walk(f)` function applies f recursively to every - component of the input entity. When an array is - encountered, f is first applied to its elements and then to - the array itself; when an object is encountered, f is first - applied to all the values and then to the object. In - practice, f will usually test the type of its input, as - illustrated in the following examples. The first example - highlights the usefulness of processing the elements of an - array of arrays before processing the array itself. The second - example shows how all the keys of all the objects within the - input can be considered for alteration. - - examples: - - program: 'walk(if type == "array" then sort else . end)' - input: '[[4, 1, 7], [8, 5, 2], [3, 6, 9]]' - output: - - '[[1,4,7],[2,5,8],[3,6,9]]' - - - program: 'walk( if type == "object" then with_entries( .key |= sub( "^_+"; "") ) else . end )' - input: '[ { "_a": { "__b": 2 } } ]' - output: - - '[{"a":{"b":2}}]' - - - title: "`have_literal_numbers`" - body: | - - This builtin returns true if jq's build configuration - includes support for preservation of input number literals. - - - title: "`have_decnum`" - body: | - - This builtin returns true if jq was built with "decnum", - which is the current literal number preserving numeric - backend implementation for jq. - - - title: "`$JQ_BUILD_CONFIGURATION`" - body: | - - This builtin binding shows the jq executable's build - configuration. Its value has no particular format, but - it can be expected to be at least the `./configure` - command-line arguments, and may be enriched in the - future to include the version strings for the build - tooling used. - - Note that this can be overriden in the command-line - with `--arg` and related options. - - - title: "`$ENV`, `env`" - body: | - - `$ENV` is an object representing the environment variables as - set when the jq program started. - - `env` outputs an object representing jq's current environment. - - At the moment there is no builtin for setting environment - variables. - - examples: - - program: '$ENV.PAGER' - input: 'null' - output: ['"less"'] - - - program: 'env.PAGER' - input: 'null' - output: ['"less"'] - - - title: "`transpose`" - body: | - - Transpose a possibly jagged matrix (an array of arrays). - Rows are padded with nulls so the result is always rectangular. - - examples: - - program: 'transpose' - input: '[[1], [2,3]]' - output: ['[[1,2],[null,3]]'] - - - title: "`bsearch(x)`" - body: | - - `bsearch(x)` conducts a binary search for x in the input - array. If the input is sorted and contains x, then - `bsearch(x)` will return its index in the array; otherwise, if - the array is sorted, it will return (-1 - ix) where ix is an - insertion point such that the array would still be sorted - after the insertion of x at ix. If the array is not sorted, - `bsearch(x)` will return an integer that is probably of no - interest. - - examples: - - program: 'bsearch(0)' - input: '[0,1]' - output: ['0'] - - program: 'bsearch(0)' - input: '[1,2,3]' - output: ['-1'] - - program: 'bsearch(4) as $ix | if $ix < 0 then .[-(1+$ix)] = 4 else . end' - input: '[1,2,3]' - output: ['[1,2,3,4]'] - - - title: "String interpolation: `\\(exp)`" - body: | - - Inside a string, you can put an expression inside parens - after a backslash. Whatever the expression returns will be - interpolated into the string. - - examples: - - program: '"The input was \(.), which is one less than \(.+1)"' - input: '42' - output: ['"The input was 42, which is one less than 43"'] - - - title: "Convert to/from JSON" - body: | - - The `tojson` and `fromjson` builtins dump values as JSON texts - or parse JSON texts into values, respectively. The `tojson` - builtin differs from `tostring` in that `tostring` returns strings - unmodified, while `tojson` encodes strings as JSON strings. - - examples: - - program: '[.[]|tostring]' - input: '[1, "foo", ["foo"]]' - output: ['["1","foo","[\"foo\"]"]'] - - program: '[.[]|tojson]' - input: '[1, "foo", ["foo"]]' - output: ['["1","\"foo\"","[\"foo\"]"]'] - - program: '[.[]|tojson|fromjson]' - input: '[1, "foo", ["foo"]]' - output: ['[1,"foo",["foo"]]'] - - - title: "Format strings and escaping" - body: | - - The `@foo` syntax is used to format and escape strings, - which is useful for building URLs, documents in a language - like HTML or XML, and so forth. `@foo` can be used as a - filter on its own, the possible escapings are: - - * `@text`: - - Calls `tostring`, see that function for details. - - * `@json`: - - Serializes the input as JSON. - - * `@html`: - - Applies HTML/XML escaping, by mapping the characters - `<>&'"` to their entity equivalents `<`, `>`, - `&`, `'`, `"`. - - * `@uri`: - - Applies percent-encoding, by mapping all reserved URI - characters to a `%XX` sequence. - - * `@csv`: - - The input must be an array, and it is rendered as CSV - with double quotes for strings, and quotes escaped by - repetition. - - * `@tsv`: - - The input must be an array, and it is rendered as TSV - (tab-separated values). Each input array will be printed as - a single line. Fields are separated by a single - tab (ascii `0x09`). Input characters line-feed (ascii `0x0a`), - carriage-return (ascii `0x0d`), tab (ascii `0x09`) and - backslash (ascii `0x5c`) will be output as escape sequences - `\n`, `\r`, `\t`, `\\` respectively. - - * `@sh`: - - The input is escaped suitable for use in a command-line - for a POSIX shell. If the input is an array, the output - will be a series of space-separated strings. - - * `@base64`: - - The input is converted to base64 as specified by RFC 4648. - - * `@base64d`: - - The inverse of `@base64`, input is decoded as specified by RFC 4648. - Note\: If the decoded string is not UTF-8, the results are undefined. - - This syntax can be combined with string interpolation in a - useful way. You can follow a `@foo` token with a string - literal. The contents of the string literal will *not* be - escaped. However, all interpolations made inside that string - literal will be escaped. For instance, - - @uri "https://www.google.com/search?q=\(.search)" - - will produce the following output for the input - `{"search":"what is jq?"}`: - - "https://www.google.com/search?q=what%20is%20jq%3F" - - Note that the slashes, question mark, etc. in the URL are - not escaped, as they were part of the string literal. - - examples: - - program: '@html' - input: '"This works if x < y"' - output: ['"This works if x < y"'] - - - program: '@sh "echo \(.)"' - input: "\"O'Hara's Ale\"" - output: ["\"echo 'O'\\\\''Hara'\\\\''s Ale'\""] - - - program: '@base64' - input: '"This is a message"' - output: ['"VGhpcyBpcyBhIG1lc3NhZ2U="'] - - - program: '@base64d' - input: '"VGhpcyBpcyBhIG1lc3NhZ2U="' - output: ['"This is a message"'] - - - title: "Dates" - body: | - - jq provides some basic date handling functionality, with some - high-level and low-level builtins. In all cases these - builtins deal exclusively with time in UTC. - - The `fromdateiso8601` builtin parses datetimes in the ISO 8601 - format to a number of seconds since the Unix epoch - (1970-01-01T00:00:00Z). The `todateiso8601` builtin does the - inverse. - - The `fromdate` builtin parses datetime strings. Currently - `fromdate` only supports ISO 8601 datetime strings, but in the - future it will attempt to parse datetime strings in more - formats. - - The `todate` builtin is an alias for `todateiso8601`. - - The `now` builtin outputs the current time, in seconds since - the Unix epoch. - - Low-level jq interfaces to the C-library time functions are - also provided: `strptime`, `strftime`, `strflocaltime`, - `mktime`, `gmtime`, and `localtime`. Refer to your host - operating system's documentation for the format strings used - by `strptime` and `strftime`. Note: these are not necessarily - stable interfaces in jq, particularly as to their localization - functionality. - - The `gmtime` builtin consumes a number of seconds since the - Unix epoch and outputs a "broken down time" representation of - Greenwich Mean Time as an array of numbers representing - (in this order): the year, the month (zero-based), the day of - the month (one-based), the hour of the day, the minute of the - hour, the second of the minute, the day of the week, and the - day of the year -- all one-based unless otherwise stated. The - day of the week number may be wrong on some systems for dates - before March 1st 1900, or after December 31 2099. - - The `localtime` builtin works like the `gmtime` builtin, but - using the local timezone setting. - - The `mktime` builtin consumes "broken down time" - representations of time output by `gmtime` and `strptime`. - - The `strptime(fmt)` builtin parses input strings matching the - `fmt` argument. The output is in the "broken down time" - representation consumed by `gmtime` and output by `mktime`. - - The `strftime(fmt)` builtin formats a time (GMT) with the - given format. The `strflocaltime` does the same, but using - the local timezone setting. - - The format strings for `strptime` and `strftime` are described - in typical C library documentation. The format string for ISO - 8601 datetime is `"%Y-%m-%dT%H:%M:%SZ"`. - - jq may not support some or all of this date functionality on - some systems. In particular, the `%u` and `%j` specifiers for - `strptime(fmt)` are not supported on macOS. - - examples: - - program: 'fromdate' - input: '"2015-03-05T23:51:47Z"' - output: ['1425599507'] - - - program: 'strptime("%Y-%m-%dT%H:%M:%SZ")' - input: '"2015-03-05T23:51:47Z"' - output: ['[2015,2,5,23,51,47,4,63]'] - - - program: 'strptime("%Y-%m-%dT%H:%M:%SZ")|mktime' - input: '"2015-03-05T23:51:47Z"' - output: ['1425599507'] - - - title: "SQL-Style Operators" - body: | - - jq provides a few SQL-style operators. - - * INDEX(stream; index_expression): - - This builtin produces an object whose keys are computed by - the given index expression applied to each value from the - given stream. - - * JOIN($idx; stream; idx_expr; join_expr): - - This builtin joins the values from the given stream to the - given index. The index's keys are computed by applying the - given index expression to each value from the given stream. - An array of the value in the stream and the corresponding - value from the index is fed to the given join expression to - produce each result. - - * JOIN($idx; stream; idx_expr): - - Same as `JOIN($idx; stream; idx_expr; .)`. - - * JOIN($idx; idx_expr): - - This builtin joins the input `.` to the given index, applying - the given index expression to `.` to compute the index key. - The join operation is as described above. - - * IN(s): - - This builtin outputs `true` if `.` appears in the given - stream, otherwise it outputs `false`. - - * IN(source; s): - - This builtin outputs `true` if any value in the source stream - appears in the second stream, otherwise it outputs `false`. - - - title: "`builtins`" - body: | - - Returns a list of all builtin functions in the format `name/arity`. - Since functions with the same name but different arities are considered - separate functions, `all/0`, `all/1`, and `all/2` would all be present - in the list. - - - title: Conditionals and Comparisons - entries: - - title: "`==`, `!=`" - body: | - - The expression 'a == b' will produce 'true' if the results of evaluating - a and b are equal (that is, if they represent equivalent JSON values) and - 'false' otherwise. In particular, strings are never considered equal - to numbers. In checking for the equality of JSON objects, the ordering of keys - is irrelevant. If you're coming from JavaScript, please note that jq's `==` is like - JavaScript's `===`, the "strict equality" operator. - - != is "not equal", and 'a != b' returns the opposite value of 'a == b' - - examples: - - program: '. == false' - input: 'null' - output: ['false'] - - - program: '. == {"b": {"d": (4 + 1e-20), "c": 3}, "a":1}' - input: '{"a":1, "b": {"c": 3, "d": 4}}' - output: ['true'] - - - program: '.[] == 1' - input: '[1, 1.0, "1", "banana"]' - output: ['true', 'true', 'false', 'false'] - - - title: if-then-else-end - body: | - - `if A then B else C end` will act the same as `B` if `A` - produces a value other than false or null, but act the same - as `C` otherwise. - - `if A then B end` is the same as `if A then B else . end`. - That is, the `else` branch is optional, and if absent is the - same as `.`. This also applies to `elif` with absent ending `else` branch. - - Checking for false or null is a simpler notion of - "truthiness" than is found in JavaScript or Python, but it - means that you'll sometimes have to be more explicit about - the condition you want. You can't test whether, e.g. a - string is empty using `if .name then A else B end`; you'll - need something like `if .name == "" then A else B end` instead. - - If the condition `A` produces multiple results, then `B` is evaluated - once for each result that is not false or null, and `C` is evaluated - once for each false or null. - - More cases can be added to an if using `elif A then B` syntax. - - examples: - - program: |- - if . == 0 then - "zero" - elif . == 1 then - "one" - else - "many" - end - input: '2' - output: ['"many"'] - - - title: "`>`, `>=`, `<=`, `<`" - body: | - - The comparison operators `>`, `>=`, `<=`, `<` return whether - their left argument is greater than, greater than or equal - to, less than or equal to or less than their right argument - (respectively). - - The ordering is the same as that described for `sort`, above. - - examples: - - program: '. < 5' - input: '2' - output: ['true'] - - - title: "`and`, `or`, `not`" - body: | - - jq supports the normal Boolean operators `and`, `or`, `not`. - They have the same standard of truth as if expressions - - `false` and `null` are considered "false values", and - anything else is a "true value". - - If an operand of one of these operators produces multiple - results, the operator itself will produce a result for each input. - - `not` is in fact a builtin function rather than an operator, - so it is called as a filter to which things can be piped - rather than with special syntax, as in `.foo and .bar | - not`. - - These three only produce the values `true` and `false`, and - so are only useful for genuine Boolean operations, rather - than the common Perl/Python/Ruby idiom of - "value_that_may_be_null or default". If you want to use this - form of "or", picking between two values rather than - evaluating a condition, see the `//` operator below. - - examples: - - program: '42 and "a string"' - input: 'null' - output: ['true'] - - program: '(true, false) or false' - input: 'null' - output: ['true', 'false'] - - program: '(true, true) and (true, false)' - input: 'null' - output: ['true', 'false', 'true', 'false'] - - program: '[true, false | not]' - input: 'null' - output: ['[false, true]'] - - - title: "Alternative operator: `//`" - body: | - - The `//` operator produces all the values of its left-hand - side that are neither `false` nor `null`. If the - left-hand side produces no values other than `false` or - `null`, then `//` produces all the values of its right-hand - side. - - A filter of the form `a // b` produces all the results of - `a` that are not `false` or `null`. If `a` produces no - results, or no results other than `false` or `null`, then `a - // b` produces the results of `b`. - - This is useful for providing defaults: `.foo // 1` will - evaluate to `1` if there's no `.foo` element in the - input. It's similar to how `or` is sometimes used in Python - (jq's `or` operator is reserved for strictly Boolean - operations). - - Note: `some_generator // defaults_here` is not the same - as `some_generator | . // defaults_here`. The latter will - produce default values for all non-`false`, non-`null` - values of the left-hand side, while the former will not. - Precedence rules can make this confusing. For example, in - `false, 1 // 2` the left-hand side of `//` is `1`, not - `false, 1` -- `false, 1 // 2` parses the same way as `false, - (1 // 2)`. In `(false, null, 1) | . // 42` the left-hand - side of `//` is `.`, which always produces just one value, - while in `(false, null, 1) // 42` the left-hand side is a - generator of three values, and since it produces a - value other `false` and `null`, the default `42` is not - produced. - - examples: - - program: 'empty // 42' - input: 'null' - output: ['42'] - - program: '.foo // 42' - input: '{"foo": 19}' - output: ['19'] - - program: '.foo // 42' - input: '{}' - output: ['42'] - - program: '(false, null, 1) // 42' - input: 'null' - output: ['1'] - - program: '(false, null, 1) | . // 42' - input: 'null' - output: ['42', '42', '1'] - - - title: try-catch - body: | - - Errors can be caught by using `try EXP catch EXP`. The first - expression is executed, and if it fails then the second is - executed with the error message. The output of the handler, - if any, is output as if it had been the output of the - expression to try. - - The `try EXP` form uses `empty` as the exception handler. - - examples: - - program: 'try .a catch ". is not an object"' - input: 'true' - output: ['". is not an object"'] - - program: '[.[]|try .a]' - input: '[{}, true, {"a":1}]' - output: ['[null, 1]'] - - program: 'try error("some exception") catch .' - input: 'true' - output: ['"some exception"'] - - - title: Breaking out of control structures - body: | - - A convenient use of try/catch is to break out of control - structures like `reduce`, `foreach`, `while`, and so on. - - For example: - - # Repeat an expression until it raises "break" as an - # error, then stop repeating without re-raising the error. - # But if the error caught is not "break" then re-raise it. - try repeat(exp) catch if .=="break" then empty else error - - jq has a syntax for named lexical labels to "break" or "go (back) to": - - label $out | ... break $out ... - - The `break $label_name` expression will cause the program to - act as though the nearest (to the left) `label $label_name` - produced `empty`. - - The relationship between the `break` and corresponding `label` - is lexical: the label has to be "visible" from the break. - - To break out of a `reduce`, for example: - - label $out | reduce .[] as $item (null; if .==false then break $out else ... end) - - The following jq program produces a syntax error: - - break $out - - because no label `$out` is visible. - - - title: "Error Suppression / Optional Operator: `?`" - body: | - - The `?` operator, used as `EXP?`, is shorthand for `try EXP`. - - examples: - - program: '[.[] | .a?]' - input: '[{}, true, {"a":1}]' - output: ['[null, 1]'] - - program: '[.[] | tonumber?]' - input: '["1", "invalid", "3", 4]' - output: ['[1, 3, 4]'] - - - title: Regular expressions - body: | - - jq uses the - [Oniguruma regular expression library](https://github.com/kkos/oniguruma/blob/master/doc/RE), - as do PHP, TextMate, Sublime Text, etc, so the - description here will focus on jq specifics. - - Oniguruma supports several flavors of regular expression, so it is important to know - that jq uses the ["Perl NG" (Perl with named groups)](https://github.com/kkos/oniguruma/blob/master/doc/SYNTAX.md) flavor. - - The jq regex filters are defined so that they can be used using - one of these patterns: - - STRING | FILTER(REGEX) - STRING | FILTER(REGEX; FLAGS) - STRING | FILTER([REGEX]) - STRING | FILTER([REGEX, FLAGS]) - - where: - - * STRING, REGEX, and FLAGS are jq strings and subject to jq string interpolation; - * REGEX, after string interpolation, should be a valid regular expression; - * FILTER is one of `test`, `match`, or `capture`, as described below. - - Since REGEX must evaluate to a JSON string, some characters that are needed - to form a regular expression must be escaped. For example, the regular expression - `\s` signifying a whitespace character would be written as `"\\s"`. - - FLAGS is a string consisting of one of more of the supported flags: - - * `g` - Global search (find all matches, not just the first) - * `i` - Case insensitive search - * `m` - Multi line mode (`.` will match newlines) - * `n` - Ignore empty matches - * `p` - Both s and m modes are enabled - * `s` - Single line mode (`^` -> `\A`, `$` -> `\Z`) - * `l` - Find longest possible matches - * `x` - Extended regex format (ignore whitespace and comments) - - To match a whitespace with the `x` flag, use `\s`, e.g. - - jq -n '"a b" | test("a\\sb"; "x")' - - Note that certain flags may also be specified within REGEX, e.g. - - jq -n '("test", "TEst", "teST", "TEST") | test("(?i)te(?-i)st")' - - evaluates to: `true`, `true`, `false`, `false`. - - entries: - - title: "`test(val)`, `test(regex; flags)`" - body: | - - Like `match`, but does not return match objects, only `true` or `false` - for whether or not the regex matches the input. - - examples: - - program: 'test("foo")' - input: '"foo"' - output: ['true'] - - program: '.[] | test("a b c # spaces are ignored"; "ix")' - input: '["xabcd", "ABC"]' - output: ['true', 'true'] - - - title: "`match(val)`, `match(regex; flags)`" - body: | - - **match** outputs an object for each match it finds. Matches have - the following fields: - - * `offset` - offset in UTF-8 codepoints from the beginning of the input - * `length` - length in UTF-8 codepoints of the match - * `string` - the string that it matched - * `captures` - an array of objects representing capturing groups. - - Capturing group objects have the following fields: - - * `offset` - offset in UTF-8 codepoints from the beginning of the input - * `length` - length in UTF-8 codepoints of this capturing group - * `string` - the string that was captured - * `name` - the name of the capturing group (or `null` if it was unnamed) - - Capturing groups that did not match anything return an offset of -1 - - examples: - - program: 'match("(abc)+"; "g")' - input: '"abc abc"' - output: - - '{"offset": 0, "length": 3, "string": "abc", "captures": [{"offset": 0, "length": 3, "string": "abc", "name": null}]}' - - '{"offset": 4, "length": 3, "string": "abc", "captures": [{"offset": 4, "length": 3, "string": "abc", "name": null}]}' - - program: 'match("foo")' - input: '"foo bar foo"' - output: ['{"offset": 0, "length": 3, "string": "foo", "captures": []}'] - - program: 'match(["foo", "ig"])' - input: '"foo bar FOO"' - output: - - '{"offset": 0, "length": 3, "string": "foo", "captures": []}' - - '{"offset": 8, "length": 3, "string": "FOO", "captures": []}' - - program: 'match("foo (?bar)? foo"; "ig")' - input: '"foo bar foo foo foo"' - output: - - '{"offset": 0, "length": 11, "string": "foo bar foo", "captures": [{"offset": 4, "length": 3, "string": "bar", "name": "bar123"}]}' - - '{"offset": 12, "length": 8, "string": "foo foo", "captures": [{"offset": -1, "length": 0, "string": null, "name": "bar123"}]}' - - - program: '[ match("."; "g")] | length' - input: '"abc"' - output: ['3'] - - - - title: "`capture(val)`, `capture(regex; flags)`" - body: | - - Collects the named captures in a JSON object, with the name - of each capture as the key, and the matched string as the - corresponding value. - - examples: - - program: 'capture("(?[a-z]+)-(?[0-9]+)")' - input: '"xyzzy-14"' - output: ['{ "a": "xyzzy", "n": "14" }'] - - - title: "`scan(regex)`, `scan(regex; flags)`" - body: | - - Emit a stream of the non-overlapping substrings of the input - that match the regex in accordance with the flags, if any - have been specified. If there is no match, the stream is empty. - To capture all the matches for each input string, use the idiom - `[ expr ]`, e.g. `[ scan(regex) ]`. - - examples: - - program: 'scan("c")' - input: '"abcdefabc"' - output: ['"c"', '"c"'] - - - title: "`split(regex; flags)`" - body: | - - Splits an input string on each regex match. - - For backwards compatibility, when called with a single argument, - `split` splits on a string, not a regex. - - examples: - - program: 'split(", *"; null)' - input: '"ab,cd, ef"' - output: ['["ab","cd","ef"]'] - - - - title: "`splits(regex)`, `splits(regex; flags)`" - body: | - - These provide the same results as their `split` counterparts, - but as a stream instead of an array. - - examples: - - program: 'splits(", *")' - input: '"ab,cd, ef, gh"' - output: ['"ab"','"cd"','"ef"','"gh"'] - - - title: "`sub(regex; tostring)`, `sub(regex; tostring; flags)`" - body: | - - Emit the string obtained by replacing the first match of - regex in the input string with `tostring`, after - interpolation. `tostring` should be a jq string or a stream - of such strings, each of which may contain references to - named captures. The named captures are, in effect, presented - as a JSON object (as constructed by `capture`) to - `tostring`, so a reference to a captured variable named "x" - would take the form: `"\(.x)"`. - - examples: - - program: 'sub("[^a-z]*(?[a-z]+)"; "Z\(.x)"; "g")' - input: '"123abc456def"' - output: ['"ZabcZdef"'] - - - program: '[sub("(?.)"; "\(.a|ascii_upcase)", "\(.a|ascii_downcase)")]' - input: '"aB"' - output: ['["AB","aB"]'] - - - title: "`gsub(regex; tostring)`, `gsub(regex; tostring; flags)`" - body: | - - `gsub` is like `sub` but all the non-overlapping occurrences of the regex are - replaced by `tostring`, after interpolation. If the second argument is a stream - of jq strings, then `gsub` will produce a corresponding stream of JSON strings. - - examples: - - program: 'gsub("(?.)[^a]*"; "+\(.x)-")' - input: '"Abcabc"' - output: ['"+A-+a-"'] - - - program: '[gsub("p"; "a", "b")]' - input: '"p"' - output: ['["a","b"]'] - - - - title: Advanced features - body: | - Variables are an absolute necessity in most programming languages, but - they're relegated to an "advanced feature" in jq. - - In most languages, variables are the only means of passing around - data. If you calculate a value, and you want to use it more than once, - you'll need to store it in a variable. To pass a value to another part - of the program, you'll need that part of the program to define a - variable (as a function parameter, object member, or whatever) in - which to place the data. - - It is also possible to define functions in jq, although this is - is a feature whose biggest use is defining jq's standard library - (many jq functions such as `map` and `select` are in fact written - in jq). - - jq has reduction operators, which are very powerful but a bit - tricky. Again, these are mostly used internally, to define some - useful bits of jq's standard library. - - It may not be obvious at first, but jq is all about generators - (yes, as often found in other languages). Some utilities are - provided to help deal with generators. - - Some minimal I/O support (besides reading JSON from standard - input, and writing JSON to standard output) is available. - - Finally, there is a module/library system. - - entries: - - title: "Variable / Symbolic Binding Operator: `... as $identifier | ...`" - body: | - - In jq, all filters have an input and an output, so manual - plumbing is not necessary to pass a value from one part of a program - to the next. Many expressions, for instance `a + b`, pass their input - to two distinct subexpressions (here `a` and `b` are both passed the - same input), so variables aren't usually necessary in order to use a - value twice. - - For instance, calculating the average value of an array of numbers - requires a few variables in most languages - at least one to hold the - array, perhaps one for each element or for a loop counter. In jq, it's - simply `add / length` - the `add` expression is given the array and - produces its sum, and the `length` expression is given the array and - produces its length. - - So, there's generally a cleaner way to solve most problems in jq than - defining variables. Still, sometimes they do make things easier, so jq - lets you define variables using `expression as $variable`. All - variable names start with `$`. Here's a slightly uglier version of the - array-averaging example: - - length as $array_length | add / $array_length - - We'll need a more complicated problem to find a situation where using - variables actually makes our lives easier. - - - Suppose we have an array of blog posts, with "author" and "title" - fields, and another object which is used to map author usernames to - real names. Our input looks like: - - {"posts": [{"title": "First post", "author": "anon"}, - {"title": "A well-written article", "author": "person1"}], - "realnames": {"anon": "Anonymous Coward", - "person1": "Person McPherson"}} - - We want to produce the posts with the author field containing a real - name, as in: - - {"title": "First post", "author": "Anonymous Coward"} - {"title": "A well-written article", "author": "Person McPherson"} - - We use a variable, $names, to store the realnames object, so that we - can refer to it later when looking up author usernames: - - .realnames as $names | .posts[] | {title, author: $names[.author]} - - The expression `exp as $x | ...` means: for each value of expression - `exp`, run the rest of the pipeline with the entire original input, and - with `$x` set to that value. Thus `as` functions as something of a - foreach loop. - - Just as `{foo}` is a handy way of writing `{foo: .foo}`, so - `{$foo}` is a handy way of writing `{foo: $foo}`. - - Multiple variables may be declared using a single `as` expression by - providing a pattern that matches the structure of the input - (this is known as "destructuring"): - - . as {realnames: $names, posts: [$first, $second]} | ... - - The variable declarations in array patterns (e.g., `. as - [$first, $second]`) bind to the elements of the array in from - the element at index zero on up, in order. When there is no - value at the index for an array pattern element, `null` is - bound to that variable. - - Variables are scoped over the rest of the expression that defines - them, so - - .realnames as $names | (.posts[] | {title, author: $names[.author]}) - - will work, but - - (.realnames as $names | .posts[]) | {title, author: $names[.author]} - - won't. - - For programming language theorists, it's more accurate to - say that jq variables are lexically-scoped bindings. In - particular there's no way to change the value of a binding; - one can only setup a new binding with the same name, but which - will not be visible where the old one was. - - examples: - - program: '.bar as $x | .foo | . + $x' - input: '{"foo":10, "bar":200}' - output: ['210'] - - program: '. as $i|[(.*2|. as $i| $i), $i]' - input: '5' - output: ['[10,5]'] - - program: '. as [$a, $b, {c: $c}] | $a + $b + $c' - input: '[2, 3, {"c": 4, "d": 5}]' - output: ['9'] - - program: '.[] as [$a, $b] | {a: $a, b: $b}' - input: '[[0], [0, 1], [2, 1, 0]]' - output: ['{"a":0,"b":null}', '{"a":0,"b":1}', '{"a":2,"b":1}'] - - - title: 'Destructuring Alternative Operator: `?//`' - body: | - - The destructuring alternative operator provides a concise mechanism - for destructuring an input that can take one of several forms. - - Suppose we have an API that returns a list of resources and events - associated with them, and we want to get the user_id and timestamp of - the first event for each resource. The API (having been clumsily - converted from XML) will only wrap the events in an array if the resource - has multiple events: - - {"resources": [{"id": 1, "kind": "widget", "events": {"action": "create", "user_id": 1, "ts": 13}}, - {"id": 2, "kind": "widget", "events": [{"action": "create", "user_id": 1, "ts": 14}, {"action": "destroy", "user_id": 1, "ts": 15}]}]} - - We can use the destructuring alternative operator to handle this structural change simply: - - .resources[] as {$id, $kind, events: {$user_id, $ts}} ?// {$id, $kind, events: [{$user_id, $ts}]} | {$user_id, $kind, $id, $ts} - - Or, if we aren't sure if the input is an array of values or an object: - - .[] as [$id, $kind, $user_id, $ts] ?// {$id, $kind, $user_id, $ts} | ... - - Each alternative need not define all of the same variables, but all named - variables will be available to the subsequent expression. Variables not - matched in the alternative that succeeded will be `null`: - - .resources[] as {$id, $kind, events: {$user_id, $ts}} ?// {$id, $kind, events: [{$first_user_id, $first_ts}]} | {$user_id, $first_user_id, $kind, $id, $ts, $first_ts} - - Additionally, if the subsequent expression returns an error, the - alternative operator will attempt to try the next binding. Errors - that occur during the final alternative are passed through. - - [[3]] | .[] as [$a] ?// [$b] | if $a != null then error("err: \($a)") else {$a,$b} end - - examples: - - program: '.[] as {$a, $b, c: {$d, $e}} ?// {$a, $b, c: [{$d, $e}]} | {$a, $b, $d, $e}' - input: '[{"a": 1, "b": 2, "c": {"d": 3, "e": 4}}, {"a": 1, "b": 2, "c": [{"d": 3, "e": 4}]}]' - output: ['{"a":1,"b":2,"d":3,"e":4}', '{"a":1,"b":2,"d":3,"e":4}'] - - program: '.[] as {$a, $b, c: {$d}} ?// {$a, $b, c: [{$e}]} | {$a, $b, $d, $e}' - input: '[{"a": 1, "b": 2, "c": {"d": 3, "e": 4}}, {"a": 1, "b": 2, "c": [{"d": 3, "e": 4}]}]' - output: ['{"a":1,"b":2,"d":3,"e":null}', '{"a":1,"b":2,"d":null,"e":4}'] - - program: '.[] as [$a] ?// [$b] | if $a != null then error("err: \($a)") else {$a,$b} end' - input: '[[3]]' - output: ['{"a":null,"b":3}'] - - - title: 'Defining Functions' - body: | - - You can give a filter a name using "def" syntax: - - def increment: . + 1; - - From then on, `increment` is usable as a filter just like a - builtin function (in fact, this is how many of the builtins - are defined). A function may take arguments: - - def map(f): [.[] | f]; - - Arguments are passed as _filters_ (functions with no - arguments), _not_ as values. The same argument may be - referenced multiple times with different inputs (here `f` is - run for each element of the input array). Arguments to a - function work more like callbacks than like value arguments. - This is important to understand. Consider: - - def foo(f): f|f; - 5|foo(.*2) - - The result will be 20 because `f` is `.*2`, and during the - first invocation of `f` `.` will be 5, and the second time it - will be 10 (5 * 2), so the result will be 20. Function - arguments are filters, and filters expect an input when - invoked. - - If you want the value-argument behaviour for defining simple - functions, you can just use a variable: - - def addvalue(f): f as $f | map(. + $f); - - Or use the short-hand: - - def addvalue($f): ...; - - With either definition, `addvalue(.foo)` will add the current - input's `.foo` field to each element of the array. Do note - that calling `addvalue(.[])` will cause the `map(. + $f)` part - to be evaluated once per value in the value of `.` at the call - site. - - Multiple definitions using the same function name are allowed. - Each re-definition replaces the previous one for the same - number of function arguments, but only for references from - functions (or main program) subsequent to the re-definition. - See also the section below on scoping. - - examples: - - program: 'def addvalue(f): . + [f]; map(addvalue(.[0]))' - input: '[[1,2],[10,20]]' - output: ['[[1,2,1], [10,20,10]]'] - - program: 'def addvalue(f): f as $x | map(. + $x); addvalue(.[0])' - input: '[[1,2],[10,20]]' - output: ['[[1,2,1,2], [10,20,1,2]]'] - - - title: 'Scoping' - body: | - - There are two types of symbols in jq: value bindings (a.k.a., - "variables"), and functions. Both are scoped lexically, - with expressions being able to refer only to symbols that - have been defined "to the left" of them. The only exception - to this rule is that functions can refer to themselves so as - to be able to create recursive functions. - - For example, in the following expression there is a binding - which is visible "to the right" of it, `... | .*3 as - $times_three | [. + $times_three] | ...`, but not "to the - left". Consider this expression now, `... | (.*3 as - $times_three | [. + $times_three]) | ...`: here the binding - `$times_three` is _not_ visible past the closing parenthesis. - - - title: "`isempty(exp)`" - body: | - - Returns true if `exp` produces no outputs, false otherwise. - - examples: - - program: 'isempty(empty)' - input: 'null' - output: ['true'] - - - program: 'isempty(.[])' - input: '[]' - output: ['true'] - - - program: 'isempty(.[])' - input: '[1,2,3]' - output: ['false'] - - - title: "`limit(n; exp)`" - body: | - - The `limit` function extracts up to `n` outputs from `exp`. - - examples: - - program: '[limit(3;.[])]' - input: '[0,1,2,3,4,5,6,7,8,9]' - output: ['[0,1,2]'] - - - title: "`first(expr)`, `last(expr)`, `nth(n; expr)`" - body: | - - The `first(expr)` and `last(expr)` functions extract the first - and last values from `expr`, respectively. - - The `nth(n; expr)` function extracts the nth value output by `expr`. - Note that `nth(n; expr)` doesn't support negative values of `n`. - - examples: - - program: '[first(range(.)), last(range(.)), nth(./2; range(.))]' - input: '10' - output: ['[0,9,5]'] - - - title: "`first`, `last`, `nth(n)`" - body: | - - The `first` and `last` functions extract the first - and last values from any array at `.`. - - The `nth(n)` function extracts the nth value of any array at `.`. - - examples: - - program: '[range(.)]|[first, last, nth(5)]' - input: '10' - output: ['[0,9,5]'] - - - title: "`reduce`" - body: | - - The `reduce` syntax allows you to combine all of the results of - an expression by accumulating them into a single answer. - The form is `reduce EXP as $var (INIT; UPDATE)`. - As an example, we'll pass `[1,2,3]` to this expression: - - reduce .[] as $item (0; . + $item) - - For each result that `.[]` produces, `. + $item` is run to - accumulate a running total, starting from 0 as the input value. - In this example, `.[]` produces the results `1`, `2`, and `3`, - so the effect is similar to running something like this: - - 0 | 1 as $item | . + $item | - 2 as $item | . + $item | - 3 as $item | . + $item - - examples: - - program: 'reduce .[] as $item (0; . + $item)' - input: '[1,2,3,4,5]' - output: ['15'] - - - program: 'reduce .[] as [$i,$j] (0; . + $i * $j)' - input: '[[1,2],[3,4],[5,6]]' - output: ['44'] - - - program: 'reduce .[] as {$x,$y} (null; .x += $x | .y += [$y])' - input: '[{"x":"a","y":1},{"x":"b","y":2},{"x":"c","y":3}]' - output: ['{"x":"abc","y":[1,2,3]}'] - - - title: "`foreach`" - body: | - - The `foreach` syntax is similar to `reduce`, but intended to - allow the construction of `limit` and reducers that produce - intermediate results. - - The form is `foreach EXP as $var (INIT; UPDATE; EXTRACT)`. - As an example, we'll pass `[1,2,3]` to this expression: - - foreach .[] as $item (0; . + $item; [$item, . * 2]) - - Like the `reduce` syntax, `. + $item` is run for each result - that `.[]` produces, but `[$item, . * 2]` is run for each - intermediate values. In this example, since the intermediate - values are `1`, `3`, and `6`, the `foreach` expression produces - `[1,2]`, `[2,6]`, and `[3,12]`. So the effect is similar - to running something like this: - - 0 | 1 as $item | . + $item | [$item, . * 2], - 2 as $item | . + $item | [$item, . * 2], - 3 as $item | . + $item | [$item, . * 2] - - When `EXTRACT` is omitted, the identity filter is used. - That is, it outputs the intermediate values as they are. - - examples: - - program: 'foreach .[] as $item (0; . + $item)' - input: '[1,2,3,4,5]' - output: ['1','3','6','10','15'] - - - program: 'foreach .[] as $item (0; . + $item; [$item, . * 2])' - input: '[1,2,3,4,5]' - output: ['[1,2]','[2,6]','[3,12]','[4,20]','[5,30]'] - - - program: 'foreach .[] as $item (0; . + 1; {index: ., $item})' - input: '["foo", "bar", "baz"]' - output: - - '{"index":1,"item":"foo"}' - - '{"index":2,"item":"bar"}' - - '{"index":3,"item":"baz"}' - - - title: Recursion - body: | - - As described above, `recurse` uses recursion, and any jq - function can be recursive. The `while` builtin is also - implemented in terms of recursion. - - Tail calls are optimized whenever the expression to the left of - the recursive call outputs its last value. In practice this - means that the expression to the left of the recursive call - should not produce more than one output for each input. - - For example: - - def recurse(f): def r: ., (f | select(. != null) | r); r; - - def while(cond; update): - def _while: - if cond then ., (update | _while) else empty end; - _while; - - def repeat(exp): - def _repeat: - exp, _repeat; - _repeat; - - - title: Generators and iterators - body: | - - Some jq operators and functions are actually generators in - that they can produce zero, one, or more values for each - input, just as one might expect in other programming - languages that have generators. For example, `.[]` - generates all the values in its input (which must be an - array or an object), `range(0; 10)` generates the integers - between 0 and 10, and so on. - - Even the comma operator is a generator, generating first - the values generated by the expression to the left of the - comma, then the values generated by the expression on the - right of the comma. - - The `empty` builtin is the generator that produces zero - outputs. The `empty` builtin backtracks to the preceding - generator expression. - - All jq functions can be generators just by using builtin - generators. It is also possible to construct new generators - using only recursion and the comma operator. If - recursive calls are "in tail position" then the - generator will be efficient. In the example below the - recursive call by `_range` to itself is in tail position. - The example shows off three advanced topics: tail recursion, - generator construction, and sub-functions. - - examples: - - program: 'def range(init; upto; by): - def _range: - if (by > 0 and . < upto) or (by < 0 and . > upto) - then ., ((.+by)|_range) - else . end; - if by == 0 then init else init|_range end | - select((by > 0 and . < upto) or (by < 0 and . > upto)); - range(0; 10; 3)' - input: 'null' - output: ['0', '3', '6', '9'] - - program: 'def while(cond; update): - def _while: - if cond then ., (update | _while) else empty end; - _while; - [while(.<100; .*2)]' - input: '1' - output: ['[1,2,4,8,16,32,64]'] - - - title: 'Math' - body: | - - jq currently only has IEEE754 double-precision (64-bit) floating - point number support. - - Besides simple arithmetic operators such as `+`, jq also has most - standard math functions from the C math library. C math functions - that take a single input argument (e.g., `sin()`) are available as - zero-argument jq functions. C math functions that take two input - arguments (e.g., `pow()`) are available as two-argument jq - functions that ignore `.`. C math functions that take three input - arguments are available as three-argument jq functions that ignore - `.`. - - Availability of standard math functions depends on the - availability of the corresponding math functions in your operating - system and C math library. Unavailable math functions will be - defined but will raise an error. - - One-input C math functions: `acos` `acosh` `asin` `asinh` `atan` - `atanh` `cbrt` `ceil` `cos` `cosh` `erf` `erfc` `exp` `exp10` - `exp2` `expm1` `fabs` `floor` `gamma` `j0` `j1` `lgamma` `log` - `log10` `log1p` `log2` `logb` `nearbyint` `rint` `round` - `significand` `sin` `sinh` `sqrt` `tan` `tanh` `tgamma` `trunc` - `y0` `y1`. - - Two-input C math functions: `atan2` `copysign` `drem` `fdim` - `fmax` `fmin` `fmod` `frexp` `hypot` `jn` `ldexp` `modf` - `nextafter` `nexttoward` `pow` `remainder` `scalb` `scalbln` `yn`. - - Three-input C math functions: `fma`. - - See your system's manual for more information on each of these. - - - title: 'I/O' - body: | - - At this time jq has minimal support for I/O, mostly in the - form of control over when inputs are read. Two builtins functions - are provided for this, `input` and `inputs`, that read from the - same sources (e.g., `stdin`, files named on the command-line) as - jq itself. These two builtins, and jq's own reading actions, can - be interleaved with each other. They are commonly used in combination - with the null input option `-n` to prevent one input from being read - implicitly. - - Two builtins provide minimal output capabilities, `debug`, and - `stderr`. (Recall that a jq program's output values are always - output as JSON texts on `stdout`.) The `debug` builtin can have - application-specific behavior, such as for executables that use - the libjq C API but aren't the jq executable itself. The `stderr` - builtin outputs its input in raw mode to stder with no additional - decoration, not even a newline. - - Most jq builtins are referentially transparent, and yield constant - and repeatable value streams when applied to constant inputs. - This is not true of I/O builtins. - - entries: - - title: "`input`" - body: | - - Outputs one new input. - - Note that when using `input` it is generally be necessary to - invoke jq with the `-n` command-line option, otherwise - the first entity will be lost. - - echo 1 2 3 4 | jq '[., input]' # [1,2] [3,4] - - - title: "`inputs`" - body: | - - Outputs all remaining inputs, one by one. - - This is primarily useful for reductions over a program's - inputs. Note that when using `inputs` it is generally necessary - to invoke jq with the `-n` command-line option, otherwise - the first entity will be lost. - - echo 1 2 3 | jq -n 'reduce inputs as $i (0; . + $i)' # 6 - - - title: "`debug`, `debug(msgs)`" - body: | - - These two filters are like `.` but have as a side-effect the - production of one or more messages on stderr. - - The message produced by the `debug` filter has the form - - ["DEBUG:",] - - where `` is a compact rendition of the input - value. This format may change in the future. - - The `debug(msgs)` filter is defined as `(msgs | debug | empty), .` - thus allowing great flexibility in the content of the message, - while also allowing multi-line debugging statements to be created. - - For example, the expression: - - 1 as $x | 2 | debug("Entering function foo with $x == \($x)", .) | (.+1) - - would produce the value 3 but with the following two lines - being written to stderr: - - ["DEBUG:","Entering function foo with $x == 1"] - ["DEBUG:",2] - - - title: "`stderr`" - body: | - - Prints its input in raw and compact mode to stderr with no - additional decoration, not even a newline. - - - title: "`input_filename`" - body: | - - Returns the name of the file whose input is currently being - filtered. Note that this will not work well unless jq is - running in a UTF-8 locale. - - - title: "`input_line_number`" - body: | - - Returns the line number of the input currently being filtered. - - - title: 'Streaming' - body: | - - With the `--stream` option jq can parse input texts in a streaming - fashion, allowing jq programs to start processing large JSON texts - immediately rather than after the parse completes. If you have a - single JSON text that is 1GB in size, streaming it will allow you - to process it much more quickly. - - However, streaming isn't easy to deal with as the jq program will - have `[, ]` (and a few other forms) as inputs. - - Several builtins are provided to make handling streams easier. - - The examples below use the streamed form of `[0,[1]]`, which is - `[[0],0],[[1,0],1],[[1,0]],[[1]]`. - - Streaming forms include `[, ]` (to indicate any - scalar value, empty array, or empty object), and `[]` (to - indicate the end of an array or object). Future versions of jq - run with `--stream` and `--seq` may output additional forms such - as `["error message"]` when an input text fails to parse. - - entries: - - title: "`truncate_stream(stream_expression)`" - body: | - - Consumes a number as input and truncates the corresponding - number of path elements from the left of the outputs of the - given streaming expression. - - examples: - - program: 'truncate_stream([[0],1],[[1,0],2],[[1,0]],[[1]])' - input: '1' - output: ['[[0],2]', '[[0]]'] - - - title: "`fromstream(stream_expression)`" - body: | - - Outputs values corresponding to the stream expression's - outputs. - - examples: - - program: 'fromstream(1|truncate_stream([[0],1],[[1,0],2],[[1,0]],[[1]]))' - input: 'null' - output: ['[2]'] - - - title: "`tostream`" - body: | - - The `tostream` builtin outputs the streamed form of its input. - - examples: - - program: '. as $dot|fromstream($dot|tostream)|.==$dot' - input: '[0,[1,{"a":1},{"b":2}]]' - output: ['true'] - - - title: Assignment - body: | - Assignment works a little differently in jq than in most - programming languages. jq doesn't distinguish between references - to and copies of something - two objects or arrays are either - equal or not equal, without any further notion of being "the - same object" or "not the same object". - - If an object has two fields which are arrays, `.foo` and `.bar`, - and you append something to `.foo`, then `.bar` will not get - bigger, even if you've previously set `.bar = .foo`. If you're - used to programming in languages like Python, Java, Ruby, - JavaScript, etc. then you can think of it as though jq does a full - deep copy of every object before it does the assignment (for - performance it doesn't actually do that, but that's the general - idea). - - This means that it's impossible to build circular values in jq - (such as an array whose first element is itself). This is quite - intentional, and ensures that anything a jq program can produce - can be represented in JSON. - - All the assignment operators in jq have path expressions on the - left-hand side (LHS). The right-hand side (RHS) provides values - to set to the paths named by the LHS path expressions. - - Values in jq are always immutable. Internally, assignment works - by using a reduction to compute new, replacement values for `.` that - have had all the desired assignments applied to `.`, then - outputting the modified value. This might be made clear by this - example: `{a:{b:{c:1}}} | (.a.b|=3), .`. This will output - `{"a":{"b":3}}` and `{"a":{"b":{"c":1}}}` because the last - sub-expression, `.`, sees the original value, not the modified - value. - - Most users will want to use modification assignment operators, - such as `|=` or `+=`, rather than `=`. - - Note that the LHS of assignment operators refers to a value in - `.`. Thus `$var.foo = 1` won't work as expected (`$var.foo` is - not a valid or useful path expression in `.`); use `$var | .foo = - 1` instead. - - Note too that `.a,.b=0` does not set `.a` and `.b`, but - `(.a,.b)=0` sets both. - - entries: - - title: "Update-assignment: `|=`" - body: | - This is the "update" operator `|=`. It takes a filter on the - right-hand side and works out the new value for the property - of `.` being assigned to by running the old value through this - expression. For instance, `(.foo, .bar) |= .+1` will build an - object with the `foo` field set to the input's `foo` plus 1, - and the `bar` field set to the input's `bar` plus 1. - - The left-hand side can be any general path expression; see `path()`. - - Note that the left-hand side of `|=` refers to a value in `.`. - Thus `$var.foo |= . + 1` won't work as expected (`$var.foo` is - not a valid or useful path expression in `.`); use `$var | - .foo |= . + 1` instead. - - If the right-hand side outputs no values (i.e., `empty`), then - the left-hand side path will be deleted, as with `del(path)`. - - If the right-hand side outputs multiple values, only the first - one will be used (COMPATIBILITY NOTE: in jq 1.5 and earlier - releases, it used to be that only the last one was used). - - examples: - - program: '(..|select(type=="boolean")) |= if . then 1 else 0 end' - input: '[true,false,[5,true,[true,[false]],false]]' - output: ['[1,0,[5,1,[1,[0]],0]]'] - - - title: "Arithmetic update-assignment: `+=`, `-=`, `*=`, `/=`, `%=`, `//=`" - body: | - - jq has a few operators of the form `a op= b`, which are all - equivalent to `a |= . op b`. So, `+= 1` can be used to - increment values, being the same as `|= . + 1`. - - examples: - - program: .foo += 1 - input: '{"foo": 42}' - output: ['{"foo": 43}'] - - - title: "Plain assignment: `=`" - body: | - - This is the plain assignment operator. Unlike the others, the - input to the right-hand side (RHS) is the same as the input to - the left-hand side (LHS) rather than the value at the LHS - path, and all values output by the RHS will be used (as shown - below). - - If the RHS of `=` produces multiple values, then for each such - value jq will set the paths on the left-hand side to the value - and then it will output the modified `.`. For example, - `(.a,.b) = range(2)` outputs `{"a":0,"b":0}`, then - `{"a":1,"b":1}`. The "update" assignment forms (see above) do - not do this. - - This example should show the difference between `=` and `|=`: - - Provide input `{"a": {"b": 10}, "b": 20}` to the programs - - .a = .b - - and - - .a |= .b - - The former will set the `a` field of the input to the `b` - field of the input, and produce the output `{"a": 20, "b": 20}`. - The latter will set the `a` field of the input to the `a` - field's `b` field, producing `{"a": 10, "b": 20}`. - - examples: - - program: .a = .b - input: '{"a": {"b": 10}, "b": 20}' - output: ['{"a":20,"b":20}'] - - - program: .a |= .b - input: '{"a": {"b": 10}, "b": 20}' - output: ['{"a":10,"b":20}'] - - - program: (.a, .b) = range(3) - input: 'null' - output: - - '{"a":0,"b":0}' - - '{"a":1,"b":1}' - - '{"a":2,"b":2}' - - - program: (.a, .b) |= range(3) - input: 'null' - output: ['{"a":0,"b":0}'] - - - title: Complex assignments - body: | - Lots more things are allowed on the left-hand side of a jq assignment - than in most languages. We've already seen simple field accesses on - the left hand side, and it's no surprise that array accesses work just - as well: - - .posts[0].title = "JQ Manual" - - What may come as a surprise is that the expression on the left may - produce multiple results, referring to different points in the input - document: - - .posts[].comments |= . + ["this is great"] - - That example appends the string "this is great" to the "comments" - array of each post in the input (where the input is an object with a - field "posts" which is an array of posts). - - When jq encounters an assignment like 'a = b', it records the "path" - taken to select a part of the input document while executing a. This - path is then used to find which part of the input to change while - executing the assignment. Any filter may be used on the - left-hand side of an equals - whichever paths it selects from the - input will be where the assignment is performed. - - This is a very powerful operation. Suppose we wanted to add a comment - to blog posts, using the same "blog" input above. This time, we only - want to comment on the posts written by "stedolan". We can find those - posts using the "select" function described earlier: - - .posts[] | select(.author == "stedolan") - - The paths provided by this operation point to each of the posts that - "stedolan" wrote, and we can comment on each of them in the same way - that we did before: - - (.posts[] | select(.author == "stedolan") | .comments) |= - . + ["terrible."] - - - title: Comments - - body: | - - You can write comments in your jq filters using `#`. - - A `#` character (not part of a string) starts a comment. - All characters from `#` to the end of the line are ignored. - - If the end of the line is preceded by an odd number of backslash - characters, the following line is also considered part of the - comment and is ignored. - - For example, the following code outputs `[1,3,4,7]` - - [ - 1, - # foo \ - 2, - # bar \\ - 3, - 4, # baz \\\ - 5, \ - 6, - 7 - # comment \ - comment \ - comment - ] - - Backslash continuing the comment on the next line can be useful - when writing the "shebang" for a jq script: - - #!/bin/sh -- - # total - Output the sum of the given arguments (or stdin) - # usage: total [numbers...] - # \ - exec jq --args -MRnf "$0" -- "$@" - - $ARGS.positional | - reduce ( - if . == [] - then inputs - else .[] - end | - . as $dot | - try tonumber catch false | - if not or isnan then - @json "total: Invalid number \($dot).\n" | halt_error(1) - end - ) as $n (0; . + $n) - - The `exec` line is considered a comment by jq, so it is ignored. - But it is not ignored by `sh`, since in `sh` a backslash at the - end of the line does not continue the comment. - With this trick, when the script is invoked as `total 1 2`, - `/bin/sh -- /path/to/total 1 2` will be run, and `sh` will then - run `exec jq --args -MRnf /path/to/total -- 1 2` replacing itself - with a `jq` interpreter invoked with the specified options (`-M`, - `-R`, `-n`, `--args`), that evaluates the current file (`$0`), - with the arguments (`$@`) that were passed to `sh`. - - - title: Modules - body: | - - jq has a library/module system. Modules are files whose names end - in `.jq`. - - Modules imported by a program are searched for in a default search - path (see below). The `import` and `include` directives allow the - importer to alter this path. - - Paths in the search path are subject to various substitutions. - - For paths starting with `~/`, the user's home directory is - substituted for `~`. - - For paths starting with `$ORIGIN/`, the directory where the jq - executable is located is substituted for `$ORIGIN`. - - For paths starting with `./` or paths that are `.`, the path of - the including file is substituted for `.`. For top-level programs - given on the command-line, the current directory is used. - - Import directives can optionally specify a search path to which - the default is appended. - - The default search path is the search path given to the `-L` - command-line option, else `["~/.jq", "$ORIGIN/../lib/jq", - "$ORIGIN/../lib"]`. - - Null and empty string path elements terminate search path - processing. - - A dependency with relative path `foo/bar` would be searched for in - `foo/bar.jq` and `foo/bar/bar.jq` in the given search path. This - is intended to allow modules to be placed in a directory along - with, for example, version control files, README files, and so on, - but also to allow for single-file modules. - - Consecutive components with the same name are not allowed to avoid - ambiguities (e.g., `foo/foo`). - - For example, with `-L$HOME/.jq` a module `foo` can be found in - `$HOME/.jq/foo.jq` and `$HOME/.jq/foo/foo.jq`. - - If `$HOME/.jq` is a file, it is sourced into the main program. - - entries: - - title: "`import RelativePathString as NAME [];`" - body: | - - Imports a module found at the given path relative to a - directory in a search path. A `.jq` suffix will be added to - the relative path string. The module's symbols are prefixed - with `NAME::`. - - The optional metadata must be a constant jq expression. It - should be an object with keys like `homepage` and so on. At - this time jq only uses the `search` key/value of the metadata. - The metadata is also made available to users via the - `modulemeta` builtin. - - The `search` key in the metadata, if present, should have a - string or array value (array of strings); this is the search - path to be prefixed to the top-level search path. - - - title: "`include RelativePathString [];`" - body: | - - Imports a module found at the given path relative to a - directory in a search path as if it were included in place. A - `.jq` suffix will be added to the relative path string. The - module's symbols are imported into the caller's namespace as - if the module's content had been included directly. - - The optional metadata must be a constant jq expression. It - should be an object with keys like `homepage` and so on. At - this time jq only uses the `search` key/value of the metadata. - The metadata is also made available to users via the - `modulemeta` builtin. - - - title: "`import RelativePathString as $NAME [];`" - body: | - - Imports a JSON file found at the given path relative to a - directory in a search path. A `.json` suffix will be added to - the relative path string. The file's data will be available - as `$NAME::NAME`. - - The optional metadata must be a constant jq expression. It - should be an object with keys like `homepage` and so on. At - this time jq only uses the `search` key/value of the metadata. - The metadata is also made available to users via the - `modulemeta` builtin. - - The `search` key in the metadata, if present, should have a - string or array value (array of strings); this is the search - path to be prefixed to the top-level search path. - - - title: "`module ;`" - body: | - - This directive is entirely optional. It's not required for - proper operation. It serves only the purpose of providing - metadata that can be read with the `modulemeta` builtin. - - The metadata must be a constant jq expression. It should be - an object with keys like `homepage`. At this time jq doesn't - use this metadata, but it is made available to users via the - `modulemeta` builtin. - - - title: "`modulemeta`" - body: | - - Takes a module name as input and outputs the module's metadata - as an object, with the module's imports (including metadata) - as an array value for the `deps` key and the module's defined - functions as an array value for the `defs` key. - - Programs can use this to query a module's metadata, which they - could then use to, for example, search for, download, and - install missing dependencies. - - - title: Colors - body: | - - To configure alternative colors just set the `JQ_COLORS` - environment variable to colon-delimited list of partial terminal - escape sequences like `"1;31"`, in this order: - - - color for `null` - - color for `false` - - color for `true` - - color for numbers - - color for strings - - color for arrays - - color for objects - - color for object keys - - The default color scheme is the same as setting - `JQ_COLORS="0;90:0;39:0;39:0;39:0;32:1;39:1;39:1;34"`. - - This is not a manual for VT100/ANSI escapes. However, each of - these color specifications should consist of two numbers separated - by a semi-colon, where the first number is one of these: - - - 1 (bright) - - 2 (dim) - - 4 (underscore) - - 5 (blink) - - 7 (reverse) - - 8 (hidden) - - and the second is one of these: - - - 30 (black) - - 31 (red) - - 32 (green) - - 33 (yellow) - - 34 (blue) - - 35 (magenta) - - 36 (cyan) - - 37 (white) diff --git a/docs/content/manual/manual.yml b/docs/content/manual/manual.yml new file mode 120000 index 0000000000..e19b54da4d --- /dev/null +++ b/docs/content/manual/manual.yml @@ -0,0 +1 @@ +v1.7/manual.yml \ No newline at end of file diff --git a/docs/content/manual/v1.3/manual.yml b/docs/content/manual/v1.3/manual.yml index 8cab6204bf..549d33023c 100644 --- a/docs/content/manual/v1.3/manual.yml +++ b/docs/content/manual/v1.3/manual.yml @@ -1,11 +1,6 @@ --- headline: jq 1.3 Manual -history: | - - *The manual for the development version of jq can be found - [here](../).* - body: | A jq program is a "filter": it takes an input, and produces an diff --git a/docs/content/manual/v1.4/manual.yml b/docs/content/manual/v1.4/manual.yml index cbfb82631e..b3cc063aa3 100644 --- a/docs/content/manual/v1.4/manual.yml +++ b/docs/content/manual/v1.4/manual.yml @@ -1,11 +1,6 @@ --- headline: jq 1.4 Manual -history: | - - *The manual for the development version of jq can be found - [here](../).* - body: | A jq program is a "filter": it takes an input, and produces an diff --git a/docs/content/manual/v1.5/manual.yml b/docs/content/manual/v1.5/manual.yml index 5b803fd24b..a2dbd882c0 100644 --- a/docs/content/manual/v1.5/manual.yml +++ b/docs/content/manual/v1.5/manual.yml @@ -1,11 +1,6 @@ --- headline: jq 1.5 Manual -history: | - - *The manual for the development version of jq can be found - [here](../).* - body: | A jq program is a "filter": it takes an input, and produces an diff --git a/docs/content/manual/v1.6/manual.yml b/docs/content/manual/v1.6/manual.yml index 87c7ff671c..0f4d8c7cfa 100644 --- a/docs/content/manual/v1.6/manual.yml +++ b/docs/content/manual/v1.6/manual.yml @@ -1,11 +1,6 @@ --- headline: jq 1.6 Manual -history: | - - *The manual for the development version of jq can be found - [here](../).* - body: | A jq program is a "filter": it takes an input, and produces an diff --git a/docs/content/manual/v1.7/manual.yml b/docs/content/manual/v1.7/manual.yml index 7852fc3c5e..e3729159cc 100644 --- a/docs/content/manual/v1.7/manual.yml +++ b/docs/content/manual/v1.7/manual.yml @@ -1,11 +1,6 @@ --- headline: jq 1.7 Manual -history: | - - *The manual for the development version of jq can be found - [here](../).* - body: | A jq program is a "filter": it takes an input, and produces an diff --git a/docs/manual_schema.yml b/docs/manual_schema.yml index f4ea5d4af5..615efad196 100644 --- a/docs/manual_schema.yml +++ b/docs/manual_schema.yml @@ -1,7 +1,6 @@ type: object required: - headline - - history - body - manpage_intro - manpage_epilogue @@ -10,8 +9,6 @@ additionalProperties: false properties: headline: type: string - history: - type: string body: type: string manpage_intro: diff --git a/docs/templates/manual.html.j2 b/docs/templates/manual.html.j2 index 9a2540c8b0..812a4233ad 100644 --- a/docs/templates/manual.html.j2 +++ b/docs/templates/manual.html.j2 @@ -33,7 +33,17 @@ {%- endmacro %}

{{ headline }}

- {{ history | markdownify }} +

+ + For other versions, see + 1.7, + 1.6, + 1.5, + 1.4, + 1.3 or + development version. + +

{{ body | markdownify }} {%- for section in sections %}
{{ check_section_id(section.title | section_id) }}