Slash

A Unix shell with structured commands, composable pipelines, and first-class jobs — one grammar, end to end.

Slash

Slash is a Unix shell built around a three-stage execution model: Shape (parsed structure) → Program (lowered executable semantics, immutable) → Job (runtime instance with process group, pids, state, result). The same grammar drives parsing, syntax highlighting, completion, and editor behavior. There is no second tokenizer, no regex highlighting hack, no separate configuration language.

Slash chooses correctness over POSIX compatibility in the places shells have historically lied:

pipefail is on by default, no surface syntax to disable
Variables are scalars or lists; no implicit word-splitting
argv is never flattened to a shell string; expansion happens exactly once per word
Job state transitions monotonically: pending → running → {stopped ↔ running}* → done

What ships today

Real Unix shell. Process groups, terminal ownership, signal discipline, pipe hygiene, reaping — all CHECKLIST-verified.
Fish-class interactive UX. Syntax highlighting as you type, history autosuggestions (dim ghost text), intelligent Tab completion, smart prefix-aware Up/Down navigation, reverse-i-search via Ctrl-R, rich prompts (any zsh PROMPT works), mid-prompt [N] Done notifications (opt-in via $SLASH_NOTIFY=immediate).
key builtin for user-configurable keybindings, with layout-aware Option-key handling on macOS — key Option-L "ls -la\n" works on any Mac out of the box, no terminal config flips required.
time keyword for honest wall + user + sys timing of any pipeline, block, or control-flow construct.
Structured introspection. slash --dump-sexp, --dump-shape, --dump-program give you the parse, typed-shape, and lowered-program forms of any source. Every diagnostic carries a stable code (SHxxxx/LWxxxx/EVxxxx/EXxxxx/JBxxxx).

Install

Slash requires Zig 0.16.0.

git clone https://github.com/shreeve/slash
cd slash
zig build -Doptimize=ReleaseFast
./bin/slash --version

The bin/slash binary is self-contained — no runtime dependencies beyond libc and a TTY. Copy it anywhere on your $PATH.

Quick start

# Run interactively (in slash)
./bin/slash

# One-liner
./bin/slash -c 'echo hello, world'

# Run a script
./bin/slash my-script.sh arg1 arg2

Drop the .slashrc.example template at ~/.slashrc and uncomment the recipes you want:

# Prompt
export PROMPT='%F{#ecede8}%K{#43669d}%D{%H:%M:%S} %F{#43669d}%K{#81a1c7}%F{#ecede8} %n@%m %F{#81a1c7}%K{}%F{#ecede8}%k %~> %f'

# Editor-time abbreviations
str ll { ls -la }
str gst { git status }

# Key bindings
key Esc-L "ls -la\n"
key Esc-G "git status\n"

Documentation

The full design lives in markdown in the repo:

README — high-level overview and current capabilities
PLAN — the design constitution. The §14 test (“does this improve Command clarity, Pipeline correctness, Program composability, or Job control?”) is the rule every feature has to pass.
CHECKLIST — line-by-line operational-correctness audit (POSIX + APUE + Harvard CS61). 77/77 boxes checked.
VALIDATION — empirical log of interactive correctness runs against real software (vim, less, top, ssh, nested shells, Python/node REPLs).

A man slash page lives at docs/slash.1 in the repo. Install it manually with:

sudo install -m 644 docs/slash.1 /usr/local/share/man/man1/

Tests

166 tests covering parse, lower, runtime, builtins, signal/job discipline, and interactive editor behavior:

zig build test

CI runs on Linux + macOS for every push; status badge at the top of this page reflects the latest main.

Credits

The interactive line editor is zigline — a separate project that grew alongside slash to provide the primitives a modern shell needs: hint hooks, transient input mode, mid-prompt printAbove, and the keymap layer slash extends.