rust-grep#

A pure-Rust reimplementation of GNU grep(1) that aims to be output-compatible with the upstream tool. Passes 121/121 tests from the GNU grep 3.12 test suite.

Uses rust-pcre2 (pure Rust) for -P (Perl-compatible) mode, fancy-regex for BRE/ERE backreferences, and the regex crate otherwise.

Building#

nix build .#rust-grep
./result/bin/grep --help

The package installs grep, egrep, and fgrep (symlinks) into $out/bin.

Running the test suite#

Tests are run in a Nix sandbox. Each test script comes from the GNU grep source tarball; rust-grep is placed first on PATH (as grep/egrep/fgrep) and the script is executed against it.

# Run a single test
nix build .#checks.x86_64-linux.rust-grep-test-{name}

# View failure diff
nix log .#checks.x86_64-linux.rust-grep-test-{name}

See default.nix for the full list of test names. Tests time out after 120s.

Supported features#

All GNU grep 3.12 features exercised by the upstream test suite, including:

Basic, extended, Perl (-G/-E/-P), and fixed-string (-F) matching
Multiple patterns via repeated -e or -f FILE
-i, -v, -w, -x, -c, -l/-L, -m, -n, -b, -o, -H/-h, -q, -s
-A/-B/-C NUM and -NUM context
-r/-R recursive search with --include, --exclude, --exclude-dir
-z NUL-delimited I/O
--color=always/never/auto with GREP_COLORS support
Binary file detection, device-file skip (-D skip), -a/--binary-files=text
-T/--initial-tab, --label, --line-buffered

Known limitation#

Patterns with nested unbounded quantifiers (e.g. ((a+)*)+) trigger a MatchLimit-style error in -P mode on non-trivial inputs, mirroring PCRE2's exponential-backtracking safeguard. Short inputs and successful matches are unaffected.

Layout#

rust/grep/
  Cargo.toml
  default.nix       # Nix package + test checks
  testsuite.nix     # Per-test Nix sandbox runner
  CHANGELOG.md
  README.md
  src/
    main.rs         # CLI entrypoint and exit codes
    args.rs         # Argument parsing
    files.rs        # File and directory walking
    grep.rs         # Per-file matching, context, output formatting
    matcher.rs      # Pattern compilation and matching dispatch
    pattern.rs      # BRE-to-ERE conversion and pattern validation

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