Minishell

A minimal shell implementation written in C as part of the 42 School curriculum. This project recreates the functionality of bash, including command parsing, execution, built-in commands, and pipeline handling.

Features

Built-in Commands

• cd - Change directory
• pwd - Print working directory
• echo - Print arguments with options
• env - Display environment variables
• export - Set environment variables
• unset - Unset environment variables
• exit - Exit the shell

Advanced Features

• Pipeline Support - Execute multiple commands with pipes (|)
• Redirection - Input/output redirection (<, >, >>)
• Here Document - Handle << redirection
• Environment Variables - Full environment variable management
• Signal Handling - Proper handling of SIGINT, SIGQUIT, and other signals
• Quote Handling - Support for single and double quotes
• Command History - Using readline library for command history

Project Structure

minishell/
├── includes/
│   ├── libft.h          # Libft library header
│   └── minishell.h      # Main project header
├── Libft/               # Custom C library (42's libft)
├── srcs/
│   ├── builtin/         # Built-in command implementations
│   ├── execute/         # Command execution logic
│   ├── free/            # Memory management
│   ├── main/            # Main program entry point
│   ├── parse/           # Command parsing and tokenization
│   ├── signal/          # Signal handling
│   └── utility/         # Utility functions
├── Makefile
└── README.md

Installation

Prerequisites

• GCC compiler
• Make
• Readline library (for command history and line editing)

Rewriting

Rewrite your gnu readline library path in the Makefile

• common path -> /usr/local/lib, /usr/local/include
• if you can't find readline library, yum install readline-devel

READ_INC_FG = -I/usr/include/readline
READ_LIB_FG = -L/usr/include/readline

Building

make

Cleaning

make clean      # Remove object files
make fclean     # Remove object files and executable
make re         # Clean and rebuild

Usage

./minishell

Once running, you can use the shell like any other Unix shell:

Minishell > ls -la
Minishell > echo "Hello World"
Minishell > cd /path/to/directory
Minishell > export MY_VAR="value"
Minishell > env | grep MY_VAR
Minishell > ls | grep .c | wc -l
Minishell > cat < input.txt > output.txt
Minishell > exit

Key Components

Parsing

• Tokenizes input into commands and arguments
• Handles quotes (single and double) properly
• Supports environment variable expansion
• Validates syntax for pipes and redirections

Execution

• Fork-based process execution
• Pipeline implementation with proper file descriptor management
• Built-in command detection and execution
• External command execution via execve

Memory Management

• Careful memory allocation and deallocation
• Prevention of memory leaks
• Proper cleanup of resources

Signal Handling

• Handles Ctrl+C (SIGINT) and Ctrl+\ (SIGQUIT)
• Different behavior for main process vs child processes
• Proper signal handling during pipeline execution

Technical Details

• Language: C
• Standards: C99
• Libraries: libft (custom), readline
• Architecture: Unix-like shell implementation
• Memory Management: Manual memory management with malloc/free

Error Handling

The shell provides comprehensive error handling for:

• Invalid syntax
• Command not found
• Permission denied
• File not found
• Memory allocation failures
• Signal interruptions

Limitations

This is a minimal shell implementation and does not include:

• Advanced scripting features
• Job control
• Advanced globbing patterns
• Some advanced redirection features

Authors

This project was developed as part of the 42 School curriculum by:

• hyeonkki
• kyunkim

License

This project is part of the 42 School curriculum and follows the school's guidelines and restrictions.