rgrep: A Ruby-Based grep-like Utility

rgrep is a Ruby command-line utility designed to search plain-text data files for lines that match a pattern or regular expression. Inspired by the Unix grep command, rgrep offers flexible options for text searching and filtering. This utility can be used on both Unix-based systems and Windows, making it a portable and versatile tool for developers and system administrators.

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Table of Contents

1. Introduction
2. Features
3. Installation
4. Usage
5. Options
6. Examples
7. Error Handling
8. License

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Introduction

rgrep provides powerful pattern-matching capabilities using command-line options. It supports multiple search modes, including word search, regular expression search, and negated matching. Additional functionalities allow users to count or extract matches. With its simple interface, rgrep is a handy tool for text processing tasks.

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Features

• 🔍 Search for specific words or patterns in files.
• 📜 Supports regular expressions for advanced pattern matching.
• ❌ Option to exclude lines that match a pattern.
• 📊 Count the number of matching lines.
• ✂️ Extract matching portions from the text.
• 🛠️ Built-in error handling for invalid options or arguments.

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Installation

1. Ensure Ruby is installed on your system. Ruby Installation Guide
2. Clone or download the rgrep repository.

$ git clone https://github.com/kam-stand/rgrep-git

3. Navigate to the directory where rgrep.rb is located.

$ cd rgrep

4. Run the script using Ruby:

$ ruby rgrep.rb [options] <pattern> <filename>

Alternatively, you can make rgrep.rb executable on a Unix-based system:

$ chmod +x rgrep.rb
$ ./rgrep.rb [options] <pattern> <filename>

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Usage

On Unix-based Systems

Use the script directly:

$ path/to/rgrep/rgrep.rb [options] <pattern> <filename>

Options

Option	Description	Notes
-w <pattern>	Treats <pattern> as a word. Returns all lines containing the word.
-p <pattern>	Treats <pattern> as a regular expression. Returns all lines matching the regex.	Default option.
-v <pattern>	Treats <pattern> as a regular expression. Returns all lines not matching the regex.
-c <pattern>	Used with -w, -p, or -v. Returns the number of lines that match the pattern.	Must be used with -p.
-m <pattern>	Used with -w or -p. Returns the matched part of each line that matches the pattern.	Must be used with -p.

Examples

Example 1: Word Search

Search for the word "error" in a log file:

$ path/to/rgrep/rgrep.rb -w error /var/log/system.log

Example 2: Regular Expression Search

Search for lines containing an email address pattern:

$ path/to/rgrep/rgrep.rb -p '\b[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Z|a-z]{2,}\b' emails.txt

Example 3: Negated Matching

Find lines that do not contain the word "success":

$ path/to/rgrep/rgrep.rb -v success output.log

Example 4: Count Matching Lines

Count the number of lines that contain the word "warning":

$ path/to/rgrep/rgrep.rb -c -w warning /var/log/system.log

Example 5: Extract Matching Portions

Extract email addresses from a text file:

$ path/to/rgrep/rgrep.rb -m -p '\b[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Z|a-z]{2,}\b' emails.txt

Error Handling

rgrep includes robust error handling to ensure smooth operation and provide meaningful feedback to the user. Below are some common errors and how rgrep handles them:

• Invalid Option: If an unrecognized option is provided, rgrep will display an error message indicating the invalid option and provide a usage guide.

  $ path/to/rgrep/rgrep.rb -z pattern file.txt
  Error: Invalid option '-z'
  Usage: rgrep.rb [options] <pattern> <filename>

• Missing Pattern: If no pattern is provided, rgrep will prompt the user to supply a pattern to search for.

  $ path/to/rgrep/rgrep.rb -w
  Error: Missing pattern
  Usage: rgrep.rb [options] <pattern> <filename>

• Missing Filename: If no filename is provided, rgrep will prompt the user to supply a file to search in.

  $ path/to/rgrep/rgrep.rb -w pattern
  Error: Missing filename
  Usage: rgrep.rb [options] <pattern> <filename>

• File Not Found: If the specified file does not exist, rgrep will display an error message indicating the file could not be found.

  $ path/to/rgrep/rgrep.rb -w pattern non_existent_file.txt
  Error: File 'non_existent_file.txt' not found

• Invalid Regular Expression: If the provided regular expression is invalid, rgrep will display an error message indicating the issue with the regex.

  $ path/to/rgrep/rgrep.rb -p '[invalid_regex' file.txt
  Error: Invalid regular expression '[invalid_regex'

These error messages help users quickly identify and correct issues, ensuring a smoother experience with rgrep.