shit

Man, my shell is shit (built on top of toiletline)

Have you ever seen warnings from software that uses Bison as its parsing engine? Did you encounter any of the coreutils' error messages? Have you spent a day debugging a Bash script?

Shit is a cross-platform shell compatible with Bash and POSIX. It runs at least 3 times faster than Bash. The UX, the errors, and the interactive experience are opinionated.

Three shells in a trenchcoat

shit runs in three modes (called moods). The default mood is shit being itself, a strict superset of Bash, with the analysis and optimization stages enabled.

Before a single command runs, shit walks the whole parsed tree to optimize and analyze it. Default mood prohibits non-deterministic globs, substitutions, variables, and any other source of unexpected shell behavior. Every error or warning at that stage is called a diagnostic.

--mood, short -M, selects the mood, one of shit, bash, or sh. The default is shit. A binary symlinked as sh, dash, or bash will pick the matching mood and disable diagnostics. set --mood changes the mood at runtime. -W keeps the diagnostics but turns every error into a warning.

-I is mimicry. shit will detect sh, dash, bash shebangs and run the script inside itself in the matching mood. The in-process run keeps speed and diagnostics.

--init-moods/-L accepts a comma-separated list of moods to steal and use init files from. It defaults to the value of --mood.

The SHIT_FLAGS environment variable may be used to specify flags. The recommended set is -W -I --init-moods=shit,bash. A flag on the command line still wins.

When encountering broken flags or arguments in SHIT_FLAGS, or supplied when the binary is launched, shit acting as a login shell will skip the rc chain, and give you a rescue session to fix the config from.

Additional bullshit

The interactive mode is modern and heavily inspired by fish. It has syntax highlighting, sensible word-jumps and controls, full UTF-8 support, wide character (CJK and emoji) width handling, multiline editing, history search, and persistent history.

shit also has more than 50 builtins, each with --help. That includes every builtin from bash and POSIX standard, with the addition of:

• z, a port of zoxide
• bench, built-in benchmark infrastructure inspired by Performance Optimizer Observation Platform (poop for short)
• and more

It also bundles a busybox-style set of coreutilities behind the shitbox builtin, including calc, an arithmetic evaluator that prints in 128 bits in the default mood and keeps the 64-bit wrap in the bash and POSIX moods. A binary of the same name on PATH is preferred. A calc on PATH runs in place of the bundled one, unless the shitbox applet mode is enabled.

Development

This software was initially made as a late April Fools joke, and everything is written from scratch in a heavily macro-modified C++23 dialect I can actually stand, and is compiled with -nostdlib++ :3

staging is the development branch. It may be broken at any time. master is more stable and should usually pass all tests.

You need Clang 18 or later and GNU Make. Building the executable needs the coreutils rm and mkdir. Running the tests needs cat, diff, and printf. Checking the code needs clang-format and clang-tidy, ideally 18 or newer.

The MODE variable controls build type:

• rel is an optimized build.
• prof is an optimized build with debug symbols for profiling.
• cov is an optimized build with debug symbols for collecting coverage.
• dbg includes all symbols and Asan with Ubsan.
• cosmo is an optimized build that uses cosmoc++ from the Cosmopolitan toolchain.
• cosmo_dbg is a debug Cosmopolitan build.

The $CXXFLAGS environment variable can be used to append new flags to the build commands.

An example of the build process:

$ export MODE=<rel/prof/dbg/cov/cosmo/cosmo_dbg>
$ make
$ ./shit --help

Or use Zig. Zig only supports dbg and rel:

$ zig build --release=fast
$ ./zig-out/bin/shit --help

And install:

$ make install PREFIX=/usr/local
$ make uninstall PREFIX=/usr/local

Roadmap

Is it usable?

• Run programs.
• Work on Linux and Windows.
• Logical sequences. (&&, ||, ;)
• Pipes.
• Redirections. (>/<)
• Shell expansion. (?, [...], *, ~)
• Escaping.
• Environment variables.
• Numeric expressions.

Is it good?

• Background jobs.
• Scripting capabilities. (flow control keywords)
• Blocks and functions.
• sh-compatible.

Is it exceptional?

• bash-compatible.
• Most of shellcheck built-in as warnings.
• Own bells and whistles.
• Cross-platform replacement for common Unix programs absent on Windows.
• Arbitrary precision numeric expressions.