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Log.js

Light-weight logging for NodeJS, including a streaming log reader.

Installation

$ npm install log

Example

Log level defaults to DEBUG however here we specify info, and the stream defaults to stdout:

var Log = require('log')
  , log = new Log('info');

log.debug('preparing email');
log.info('sending email');
log.error('failed to send email');

Specifying a specific stream:

var fs = require('fs')
  , Log = require('log')
  , log = new Log('debug', fs.createWriteStream('my.log'));

Instead of the log level constants, you may also supply a string:

var Log = require('log')
  , log = new Log('warning');

We can also use %s much like console.log() to pass arguments:

 log.error('oh no, failed to send mail to %s.', user.email);

Turn colors on:

log.colorful();

Turn colors off:

log.colorful(false);

Setting up our own colors :

log.colorful({
    'EMERGENCY' : "\033[0;31m",
    'ALERT'     : "\033[0;33m",
    'CRITICAL'  : "\033[0;31m",
    'ERROR'     : "\033[1;31m",
    'WARNING'   : "\033[0;33m",
    'NOTICE'    : "\033[0;36m",
    'INFO'      : "\033[0;35m",
    'DEBUG'     : "\033[0m"
});

You don't have to specify all levels, when defining colors, if you only want to specify certain levels, you just write those:

log.colorful({
    'INFO'      : "\033[0;35m",
    'DEBUG'     : "\033[0m"
})

Setting up your own log levels:

log.customLevels([ 'COMMAND', 'DATA' ] );

Which will simple add methods command and data to the Log object, and you can use them as the way that default log methods be used, like log.command( "a command message").

Also, you can setting up your own log levels and their colors at the same time:

log.customLevels({
	COMMAND: '\033[0;31m',
	DATA: '\033[0;31m'
});

Reader

To stream a log, simply pass a readable stream instead of a writable:

var Log = require('log')
  , fs = require('fs')
  , stream = fs.createReadStream(__dirname + '/file.log')
  , log = new Log('debug', stream);

log.on('line', function(line){
  console.log(line);
});

Example stdout:

{ date: Sun, 26 Sep 2010 01:26:14 GMT
, level: 1
, levelString: 'ALERT'
, msg: 'a alert message'
}
{ date: Sun, 26 Sep 2010 01:26:14 GMT
, level: 0
, levelString: 'EMERGENCY'
, msg: 'a emergency message'
}

Log Levels

Mirror that of syslog:

  • 0 EMERGENCY system is unusable
  • 1 ALERT action must be taken immediately
  • 2 CRITICAL the system is in critical condition
  • 3 ERROR error condition
  • 4 WARNING warning condition
  • 5 NOTICE a normal but significant condition
  • 6 INFO a purely informational message
  • 7 DEBUG messages to debug an application

License

(The MIT License)

Copyright (c) 2009-2010 TJ Holowaychuk <tj@vision-media.ca>

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the 'Software'), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.