minigrep

A fast, grep-like command-line tool written in Rust. Searches one or more files for a pattern and prints matching lines with colored highlights. Supports regex, recursive search, parallel processing, and most common grep flags.

Features

• Colored output — matches highlighted in red; disabled automatically when piping
• Regex support (-E) — full regular expression engine via the regex crate
• Case-insensitive search (-i or IGNORE_CASE env var)
• Invert match (-v) — print lines that do NOT match
• Whole-word match (-w) — match only complete words
• Context lines (-C N) — show N lines before/after each match
• Count mode (-c) — print match count per file instead of lines
• Files-with-matches (-l) — print only file names that contain a match
• Max-count (-m N) — stop after N matches per file
• Recursive search (-r) — walk directories; auto-uses current dir if no path given
• Glob filters (--include/--exclude) — filter files by name pattern
• stdin support — reads from stdin when no files are provided
• Binary file safety — non-UTF-8 files are silently skipped
• Parallel processing — multiple files searched concurrently via Rayon
• Progress bar — shown when processing many files (stderr, auto-hidden in pipes)
• Correct exit codes — 0 matches found, 1 no matches, 2 error

Installation

cargo build --release
# binary is at ./target/release/minigrep

Usage

minigrep [OPTIONS] <PATTERN> [FILE]...

If no files are given, reads from stdin (unless -r is set, which defaults to .).

Options

Flag	Long form	Description
-i	--ignore-case	Case-insensitive search
-E	--regexp	Treat pattern as a regular expression
-v	--invert-match	Print lines that do NOT match
-w	--word-regexp	Match whole words only
-c	--count	Print match count per file
-l	--files-with-matches	Print only file names with matches
-m N	--max-count N	Stop after N matches per file
-C N	--context N	Show N lines of context around matches
-r	--recursive	Recurse into directories
	--include GLOB	Include only files matching this name glob
	--exclude GLOB	Exclude files matching this name glob
	--color WHEN	Color output: auto (default), always, never
-h	--help	Print help

Environment Variables

Variable	Description
IGNORE_CASE	Set to any value to enable case-insensitive mode

Examples

# Basic search
minigrep "fn main" src/main.rs

# Regex: find all function definitions
minigrep -E "^pub fn \w+" src/lib.rs

# Case-insensitive, whole words only
minigrep -i -w "error" src/lib.rs

# Recursive search through all .rs files
minigrep -r --include "*.rs" "TODO" src/

# Recursive from current directory
minigrep -r "panic"

# Show 2 lines of context around each match
minigrep -C 2 "unwrap" src/main.rs

# Count matches per file
minigrep -c "fn " src/main.rs src/lib.rs

# Print only file names that contain matches
minigrep -l "unsafe" src/

# Stop after first match per file
minigrep -m 1 "error" src/main.rs src/lib.rs

# Invert: lines that don't contain "ok"
minigrep -v "ok" results.txt

# Read from stdin
cat poem.txt | minigrep "hope"

# Disable color for piping
minigrep --color=never "fn" src/main.rs | wc -l

# Env var for case-insensitive mode
IGNORE_CASE=1 minigrep "hello" file.txt

Output Format

Normal mode:

<file>:<line>: <content with match highlighted>

Context mode (: for match lines, - for context lines, -- between groups):

src/lib.rs:23: pub fn search(
src/lib.rs-24- re: &Regex,
--
src/lib.rs:47: pub fn search_with_context(

Count mode:

src/main.rs: 5
src/lib.rs: 12

Files-with-matches mode:

src/main.rs
src/lib.rs

Exit Codes

Code	Meaning
0	At least one match found
1	No matches found
2	Error (bad pattern, unreadable file, etc.)

Dependencies

Crate	Purpose
clap	CLI argument parsing
colored	Terminal color output
regex	Regular expression engine
rayon	Parallel iteration over files
walkdir	Recursive directory traversal
globset	Glob pattern matching for --include/--exclude
indicatif	Progress bar during multi-file scan
is-terminal	Detect whether stdout/stderr is a TTY

Running Tests

cargo test