bunmsh

• bunmsh is a dependency-free, mksh-inspired cross-platform command shell for Bun
  • Bun Modern Shell
• Early releases focus on a small, usable command interpreter rather than full mksh compatibility.

Usage

Install Bun first

• bunmsh requires Bun
• On Android, install it in Termux:

npm install -g bun

On other platforms, follow the official Bun installation guide.

No project dependencies need to be installed with npm install or bun install.

Option 1: Run with npx

# Interactive shell
npx bunmsh

npx bunmsh -c 'print $PATH'

npx installs and launches the package, but the bunmsh executable itself uses Bun. Bun must therefore already be available on PATH.

Option 2: Run with git clone

After the repository is publicly available:

• Interactive shell

git clone https://github.com/jjtseng93/bunmsh.git
cd bunmsh

bun ./bunmsh

• Running commands or scripts

bun ./bunmsh -c 'print $PATH'

# bun ./bunmsh script.sh arg1 arg2

What's implemented

• Interactive prompt, standard-input scripts, script files and -c

• External commands through Bun.spawn

• Sequential pipelines (a | b)

• Command lists with ;, && and ||

• Single quotes, double quotes and backslash quoting

• $NAME, ${NAME}, $?, $$, $#, $0 through $9

• Leading environment assignments and persistent assignment-only commands

• <, >, >>, 2> and 2>>

• cd, pwd, export, unset, env, exit, set, :, true, false, echo, print and a small printf

• See PORTING.md for semantic limitations and the remaining mksh work.

Test

bun test

Built-in README

Show this README in the terminal with ANSI formatting:

bunmsh --readme

--readme reads the embedded copy first when running a standalone executable, then falls back to the repository's README.md during development.

Standalone executable

Build a single-file executable for the current platform:

bun ./src/main.js --build-exe
./bmsh --version

Cross-compile for a Bun-supported target:

bun ./src/main.js --build-for bun-linux-x64

The build writes ./bmsh and leaves the repository's ./bunmsh launcher unchanged. The executable includes README.md as an internal asset. See single-exe/README.md for asset-management options.

License

The original bunmsh JavaScript implementation is released under the MIT License, Copyright (c) 2026 Dr. John (醫者小智).

mksh is a separate upstream project and is not relicensed under MIT. Its complete licence terms remain in LICENSE-MKSH.