A lightweight grep-like command-line utility built in Node.js. It allows searching for patterns in files, directories (recursively), or standard input — mimicking core functionality of GNU grep.

• Pattern Matching

  • Supports simple substring search
  • Character classes [abc]
  • Escape sequences like \d, \w
  • Anchors ^ (start) and $ (end)
  • Alternation (word1|word2)
  • Quantifiers +, ?
  • Dot . (any character)

• Recursive Search

  • With -r, search entire directories and their subdirectories.

• Multiple File Support

  • Handles one or many files, with file names prefixed in multi-file output.

• Standard Input

  • Works with piped input when no files are specified.

• Exit Codes

  • 0 → match found
  • 1 → no match found

Clone the repo and run directly with Node:

git clone https://github.com/yourusername/grep-clone.git
cd grep-clone
node grep.js -E pattern file.txt

Optionally, make it globally accessible:

chmod +x grep.js
ln -s $(pwd)/grep.js /usr/local/bin/mygrep

Then you can use:

mygrep -E foo file.txt

node grep.js -E <pattern> [files...]
node grep.js -r -E <pattern> [directories...]

node grep.js -E hello file.txt

Matches lines containing hello.

node grep.js -r -E "error" ./logs

Matches all lines containing error across all files under logs/.

node grep.js -E "foo|bar" file.txt

Matches lines containing either foo or bar.

node grep.js -E "^[0-9]+" numbers.txt

Matches lines starting with a number.

node grep.js -E "[abc]" file.txt

Matches lines containing a, b, or c.

echo "hello world" | node grep.js -E hello

Output: hello world

• File traversal: Uses fs.readdirSync and recursion for -r to gather all files.

• Pattern Matching: Implemented via a custom matchPattern function that:

  • Detects simple patterns (includes)
  • Converts regex-like patterns into RegExp objects for matching
  • Handles anchors, alternation, and classes manually.

• I/O: Reads files line by line (fs.readFileSync + split on \n).

• CLI Arguments:

  • -E → pattern matching mode (with regex-like syntax)
  • -r → recursive directory traversal

• Pure Node.js, no external dependencies.
• Mimics grep behavior for everyday use.
• Recursive search with -r.
• Supports stdin for pipe workflows.
• Exit codes follow Unix conventions.