A minimal POSIX-compliant shell written in C that interprets commands, executes external programs, and supports built-in commands.

Documentation

• Project Motivation

Features implemented

1. Prompt display: Shows a prompt and waits for user input
2. Error handling: Gracefully handles invalid commands
3. REPL loop: Continuously reads, evaluates, and executes commands.
4. Built-in commands:
   • exit: Exit the shell
   • echo: Print text to stdout
   • type: Identify whether a command is a built-in or an executable
   • pwd: Print the current working directory
   • cd: Change directories: Absolute paths, Relative paths, Home directory (cd ~)
5. Quoting support:
   • Single quotes
   • Double quotes
   • Backslash escaping (inside and outside quotes)
   • Executing quoted executables
6. I/O Redirection:
   • Redirect stdout (>)
   • Redirect stderr (2>)
   • Append stdout (>>)
   • Append stderr (2>>)

Features To Be Implemented

1. Tab completion:

   • Built-in completion
   • Executable completion
   • Multiple and partial completions

2. Pipelines:

   • Dual-command pipelines
   • Built-in commands in pipelines
   • Multi-command pipelines

3. Command history:

   • View history
   • Up/down arrow navigation
   • Execute commands from history
   • Persistent history (save/load from file)

Tech Stack

• Language: C (C99 standard)
• Standards Compliance: POSIX
• Platform: Developed and tested on Linux. Compatible with macOS (POSIX-compliant). Windows support would require adapting process and file descriptor APIs to WinAPI.
• Build System: CMake (project configuration) with Ninja (fast incremental builds)
• Compiler: Clang (tested; GCC compatible)
• Package Manager: vcpkg for dependency management

How to run

1. clone the repository

git clone git@github.com:raphico/shell-c.git
cd shell-c

2. run the program

./your_program.sh

Project structure

├── include/              # Header files
├── src
│   ├── builtins/         # Built-in command implementations
│   ├── main.c            # Entry point: initializes and runs the shell REPL loop
│   ├── parser.c          # Tokenizes user input and parses redirection operators
│   ├── redirects.c       # Handles applying/restoring I/O redirections before/after command execution
│   └── shell.c           # Dispatches built-in commands or executes external programs
└── your_program.sh       # Shell script to run or test the program

Attribution

This project was built as part of the Codecrafters "Build Your Own Shell" Challenge