rust-bash#

A Bash-compatible shell written in Rust, targeting full compatibility with GNU Bash 5.3.

Status#

77/77 nix integration tests passing. The shell passes the full Bash 5.3 test suite used in the nix harness, covering aliases, arithmetic, arrays (indexed and associative), brace expansion, builtins, case statements, command substitution, conditionals, coprocesses, extglob, functions, globbing, heredocs, here-strings, IFS handling, mapfile, namerefs, parameter expansion, pattern matching, pipelines, printf, process substitution, quoting, redirections, traps, and more.

See CHANGELOG.md for the full fix history (300+ fixes across 117 phases).

Features#

• POSIX-compatible command execution with Bash extensions
• Indexed and associative arrays
• Nameref variables (declare -n)
• Arithmetic evaluation ((( )), $(( )), let)
• Extended globbing (extglob, globstar)
• Process substitution (<(), >())
• Coprocesses (coproc)
• Here documents and here strings
• Brace expansion
• Command substitution (`...` and $(...))
• Variable redirections ({varname}>file)
• set -e, set -x, pipefail, lastpipe
• Builtins: declare, local, export, unset, read, printf, mapfile, trap, type, command, hash, enable, shopt, set, getopts, select, and more
• Built-in help data extracted from Bash 5.3 .def files

Building#

Requires a Rust toolchain (edition 2024).

cargo build           # debug build
cargo build --release # optimized build with LTO

The binary is named bash and also symlinks to sh when installed via Nix.

With Nix#

nix build .#rust-bash          # release build
nix build .#rust-bash-dev      # debug build (faster compile)

Testing#

Nix test harness (77 tests)#

# Run a single test
nix build .#checks.x86_64-linux.rust-bash-test-NAME

# Run all tests (continue on failure)
nix build --keep-going .#checks.x86_64-linux.rust-bash-test-{alias,appendop,arith,array,...}

# View failure diff
nix log .#checks.x86_64-linux.rust-bash-test-NAME

Local testing#

cd /tmp/bash-5.3/tests
export THIS_SH=/path/to/target/debug/bash

# Single test diff against reference bash
diff <("$THIS_SH" ./NAME.tests 2>&1) <(bash ./NAME.tests 2>&1)

# Run all 83 local tests
for test in $(ls *.tests | sed 's/.tests$//' | sort); do
  diff_lines=$(timeout 60 diff <("$THIS_SH" ./${test}.tests 2>&1) \
    <(bash ./${test}.tests 2>&1) 2>&1 | wc -l)
  [ "$diff_lines" -gt 0 ] && echo "DIFF($diff_lines): $test" || echo "OK: $test"
done

Note: Some tests show spurious diffs when run in parallel due to race conditions on shared temp files. Run sequentially for accurate results. The ifs-posix test takes ~4 minutes (6856 subtests) — use timeout 300.

Architecture#

Dependencies#

• nix — Unix syscalls (process, signal, fd, poll)
• glob — Filename globbing
• libc — Low-level C bindings
• regex-lite — Lightweight regex (for =~ operator)

License#

MIT