fastgrep

A high-performance, dependency-free CLI grep replacement written in C. fastgrep is designed for maximum speed using memory-mapped I/O, SIMD-accelerated pattern matching, and multi-threaded search.

Features

• Ultra-fast file searching - Memory-mapped files for large files, buffered reading for small files
• SIMD acceleration - SSE4.2 and AVX2 support for ASCII substring search
• Multi-threaded - POSIX threads for parallel file processing
• Pattern matching - Full regex support (POSIX extended) and optimized ASCII substring search
• Case-insensitive search - Optional case-insensitive matching
• Recursive directory search - Search entire directory trees
• Rich output - ANSI color highlighting, line numbers, file names
• Cross-platform - Linux, macOS, and Windows (where supported)
• Zero dependencies - Uses only C standard library and POSIX APIs

Performance

fastgrep is optimized for raw performance:

• Memory-mapped I/O - Direct file access without copying data
• SIMD instructions - SSE4.2/AVX2 for fast pattern matching
• Multi-threading - Parallel search across multiple files
• Minimal allocations - Avoids memory allocations in hot loops
• Precompiled regex - Regex patterns compiled once and reused

Building

Prerequisites

• GCC or Clang compiler with C99 support
• POSIX-compliant system (Linux, macOS, BSD)
• Make utility

Build Instructions

# Clone the repository
git clone https://github.com/myferr/fastgrep.git
cd fastgrep

# Build with optimizations (default)
make

# Build with debug symbols
make debug

# Build with extra optimizations
make fast

# Build with AVX2 only
make avx2

# Build with SSE4.2 only
make sse42

# Install to /usr/local/bin
sudo make install

# Uninstall
sudo make uninstall

The binary will be created at bin/fstgrep.

Build Flags

The Makefile uses the following optimization flags by default:

• -O3 - Maximum optimization
• -march=native - Optimize for your CPU
• -pthread - POSIX threads
• -msse4.2 - Enable SSE4.2 instructions
• -mavx2 - Enable AVX2 instructions (if supported)

Usage

Basic Usage

# Search for a pattern in a single file
fstgrep pattern file.txt

# Search in multiple files
fstgrep pattern file1.txt file2.txt file3.txt

# Search recursively in a directory
fstgrep -r pattern /path/to/directory

# Case-insensitive search
fstgrep -i pattern file.txt

# Show line numbers
fstgrep -n pattern file.txt

# Use regex matching
fstgrep -e "error[0-9]+" file.txt

# Multi-threaded search
fstgrep --threads 4 pattern *.log

Command-Line Options

Pattern Matching:
  -e, --regex            Use regex matching (default: ASCII substring)
  -i, --ignore-case      Case-insensitive search

Search Options:
  -r, --recursive        Recursively search directories
      --threads <N>      Number of threads (default: 1)

Output Options:
  -n, --line-number      Show line numbers
      --no-line-number   Don't show line numbers
      --color            Highlight matches (default when TTY)
      --no-color         Don't highlight matches
  -q, --quiet            Quiet mode (only exit code matters)

Other Options:
  -v, --verbose          Verbose output
  -h, --help             Show help message
      --version          Show version information

Examples

# Find all occurrences of "error" in log files
fstgrep error *.log

# Find case-insensitive "hello" recursively
fstgrep -i -r hello /path/to/code

# Use regex to find error codes
fstgrep -e "error[0-9]+" application.log

# Search with line numbers and colors
fstgrep -n --color "TODO" src/

# Multi-threaded search across many files
fstgrep --threads 8 pattern /path/to/large/directory

# Quiet mode for scripts (exit code only)
fstgrep -q "critical" system.log && echo "Found!"

Architecture

fastgrep uses a modular architecture:

Source Files

• main.c - Entry point, argument parsing, orchestration
• file_reader.c - Memory-mapped and buffered file I/O, directory traversal
• regex_simd.c - SIMD-accelerated pattern matching and regex support
• search.c - Multi-threaded search logic and task queue management
• output.c - Output formatting, colors, line numbers, file names
• logger.c - Debug and performance logging

Header Files

• include/file_reader.h - File reading interfaces
• include/regex_simd.h - Pattern matching interfaces
• include/search.h - Search and threading interfaces
• include/output.h - Output formatting interfaces
• include/logger.h - Logging interfaces

Testing

Run Unit Tests

make test

Run Integration Tests

make integration

Run All Tests

make test
make integration

Performance Notes

• Memory-mapped files are used for files larger than 1MB
• SIMD acceleration is automatically enabled for ASCII patterns on supported CPUs
• Multi-threading provides near-linear speedup for multiple files
• Regex mode is slower than ASCII substring search; use ASCII when possible

Limitations

• Regex matching uses POSIX extended regex (not PCRE)
• SIMD acceleration only works for ASCII substring patterns
• Large files require sufficient virtual memory for memory mapping
• Windows support is limited to platforms with POSIX APIs

License

See LICENSE file for details.

Contributing

Contributions are welcome! Please ensure:

• Code follows the existing style
• All tests pass
• Performance optimizations are benchmarked
• Cross-platform compatibility is maintained

Version History

• 1.0.0 - Initial release
  • Memory-mapped I/O
  • SIMD-accelerated search (SSE4.2/AVX2)
  • Multi-threaded processing
  • Full regex support
  • ANSI color output
  • Line numbers and file names