Minishell - A simple recreation of Bash

A compact yet fully functional UNIX shell written in C.
This project replicates the core behavior of bash, implementing command parsing, built-in commands, pipes, redirections, environment variable expansion, and more — all from scratch.

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Overview

The goal of Minishell is to understand how a real shell works internally:
how user input is parsed, commands are executed, and processes interact with the operating system.

This project builds a strong foundation in system programming, especially process handling, file descriptors, and command interpretation.

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Installation

Clone and compile the project:

git clone https://github.com/mdomnik/minishell.git
cd minishell
make

Run the shell:

./minishell

You can exit the shell with:

exit

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Features

Built-in Commands

• echo (with -n flag)
• cd (supports relative, absolute, and -)
• pwd
• export, unset, env
• exit

External Commands

• Executes binaries found in $PATH
• Handles absolute and relative paths
• Preserves environment variables between commands

Pipes & Redirections

• Pipelines (cmd1 | cmd2 | cmd3)
• Input <, output >, append >> redirections
• Heredocs (<<) with proper delimiter behavior

Environment & Quoting

• $VAR expansion (inside double quotes)
• Single quotes preserve literal strings
• Works with redirections and pipes

Signal Handling

• Ctrl+C interrupts current command but not the shell
• Ctrl+\ and Ctrl+D handled gracefully

Error & Status Handling

• Accurate exit codes ($?)
• Clear error messages for invalid commands, files, or paths
• Behavior aligned with bash

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Demonstrated in the Showcase

The GIF demo above shows:

• Builtins such as cd, echo, export, unset, env
• External command execution (ls, grep, wc, cat, etc.)
• Redirections (>, >>, <) and heredocs (<<)
• Pipelining between commands
• Variable expansion and quoting rules
• Error handling and $? exit status
• Clean exit from the shell

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Technical Insights

• Custom lexer and parser for tokenizing input and building commands
• Use of fork() / execve() for executing child processes
• Management of pipe() and dup2() for I/O redirections and pipelines
• Environment variable storage and expansion logic
• Signal handling using sigaction() to replicate bash-style behavior

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Project Structure

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├── minishell          # Compiled shell binary
├── Makefile           # Build rules
├── inc/               # Headers
├── src/               # Source code (lexer, parser, executor, builtins, utils, ...)
├── lib/               # libft (custom standard library)
├── obj/               # Object files
├── suppressions.supp  # Valgrind suppression file
└── Showcase.gif       # Feature demo

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Author

Maciej — @mdomnik
Kang — @donkeykang316