py-posix-shell 0.1.0

A small cross-platform POSIX-style shell written in Python.

py-posix-shell

py-posix-shell is a small POSIX-style shell implemented in pure Python. It is intended to run on Windows, Linux, and macOS with the same Python package and the same console entry point.

The project focuses on a practical, compact subset of POSIX shell behavior:

• command lists with ;, &&, ||, and background &
• pipelines with |
• quoting with single quotes, double quotes, and backslash escapes
• parameter expansion such as $HOME, $?, ${name:-word}, and ${name:=word}
• command substitution with $(...) and backticks
• field splitting, pathname expansion, and tilde expansion
• redirection with <, >, >>, 2>, 2>>, >&, and <&
• shell variables, exported environment variables, and positional parameters
• common builtins including cd, pwd, exit, export, unset, set, shift, echo, printf, read, type, command, env, test, and [

It deliberately does not try to be a full replacement for dash, bash, or zsh. Complex POSIX features such as functions, aliases, job control, traps, arithmetic expansion, case/esac, for/while/until loops, and here-documents are not implemented yet.

Installation

From this repository:

pip install .

For editable development:

pip install -e ".[dev]"

Usage

Start an interactive shell:

pysh

Run one command:

pysh -c "name=world; echo \"hello $name\""

Run a script:

pysh ./script.sh arg1 arg2

The package also installs the longer py-posix-shell command.

Development

Run the tests with:

pytest

The implementation uses only the Python standard library at runtime.