rust-shell

A POSIX-style shell implemented in Rust as a learning project through the CodeCrafters shell challenge.

What this project demonstrates

• Lexing and parsing shell input into pipelines and command invocations
• Execution of built-in commands and external programs
• Output/error redirection and pipeline composition
• Background job tracking
• Simple shell state management for history, variable declaration, and completion records
• A REPL built on rustyline

Implemented shell behavior

• Built-ins: cd, pwd, echo, type, exit, history, jobs, declare, complete
• Pipelines with |
• Background execution with &
• Redirection: >, >>, 2>, 2>>
• Basic argument parsing with quotes and escapes
• Variable expansion for declared values

Technical notes

• Language: Rust
• Edition: 2021
• Primary dependencies: rustyline, regex
• Structure:
  • src/syntax: lexer, tokens, parser
  • src/commands: built-ins, expansion, execution, redirection, command resolution
  • src/state: in-memory stores for history, jobs, declarations, completions
  • src/repl: interactive shell session

Test coverage

The unit test suite focuses on the parts most likely to cause behavioral regressions:

• lexical scanning
• parsing
• argument expansion
• redirection and executable resolution
• state stores
• selected built-ins with meaningful logic

Current project-source coverage is above 60%.

Running locally

./your_program.sh

Run tests with:

cargo test

Why this repo exists

This is not intended to be a production shell. It is a systems programming exercise focused on parser design, process orchestration, and building a clean command execution flow in Rust.