A POSIX shell implementation written in Zig.

tsh implements the POSIX.1-2017 shell command language specification, including lexing, parsing, word expansion, and command execution. It links libc for POSIX process management and filesystem operations.

Requires Zig 0.15.2+. A Nix flake is provided for reproducible builds.

# Using Nix
nix develop .#tsh
zig build

# Or directly with Zig
zig build
zig build -Doptimize=ReleaseSafe

# Nix package
nix build

# Interactive mode
zig build run

# Run a command
zig build run -- -c 'echo hello'

# Run a script
zig build run -- script.sh

• Simple commands with argument lists
• Pipelines (cmd1 | cmd2 | cmd3)
• AND/OR lists (cmd1 && cmd2, cmd1 || cmd2)
• I/O redirections (>, >>, <, 2>, >&)
• Subshells for pipeline stages

• if / elif / else / fi
• while / until loops
• for name in words; do ...; done
• break and continue with nesting depth

• Tilde expansion (~, ~/path)
• Parameter expansion ($VAR, ${VAR}, ${VAR:-default}, ${VAR:+alt}, ${VAR:=assign}, ${VAR:?error}, ${#VAR}, ${VAR%pat}, ${VAR%%pat}, ${VAR#pat}, ${VAR##pat})
• Command substitution ($(cmd))
• Special parameters ($?, $#, $@, $*, $0, $$)
• Field splitting on IFS (custom IFS support)
• Pathname expansion / globbing (*, ?, [...])
• Quote removal (single quotes, double quotes, backslash escaping)

cd, exit, export, pwd, test / [, unset

• Arithmetic expansion ($((expr)))
• Here-documents (<<)
• Backtick command substitution (`cmd`)
• case statements
• Functions
• Job control
• Signal handling
• set, readonly, eval, exec, ./source, read, trap

# Run all tests
zig build test

# Run tests for a specific module
zig test src/lexer.zig --dep tsh -Mroot=src/root.zig
zig test src/expand.zig --dep tsh -Mroot=src/root.zig

# Dump token stream
zig build run -- --dump-tokens < script.sh

# Dump AST
zig build run -- --dump-ast < script.sh