Minishell

A simplified shell implementation written in C, inspired by bash. This project is part of the 42 curriculum and demonstrates core shell functionality including command parsing, execution, piping, redirections, and built-in commands.

Features

Core Shell Functionality

• Interactive prompt with command history using GNU readline
• Command parsing with Abstract Syntax Tree (AST) construction
• Command execution with proper process management
• Environment variable management and expansion
• Signal handling for SIGINT (Ctrl+C) and SIGQUIT (Ctrl+)

Supported Features

• Pipes (|) - Connect multiple commands
• Redirections:
  • Input redirection (<)
  • Output redirection (>)
  • Append mode (>>)
  • Heredocs (<<)
• Quotes handling:
  • Single quotes (') - literal interpretation
  • Double quotes (") - allow variable expansion
• Variable expansion ($VAR and $? for exit status)

Built-in Commands

Command	Description
echo	Display text with -n option support
cd	Change current directory
pwd	Print working directory
env	Display environment variables
export	Set/export environment variables
unset	Remove environment variables
exit	Exit the shell with optional exit code

Project Structure

.
├── include/          # Header files
├── src/
│   ├── builtins/     # Built-in command implementations
│   ├── core/         # Main shell logic and memory management
│   ├── environment/  # Environment variable handling
│   ├── error/        # Error handling
│   ├── executor/     # Command execution logic
│   ├── expansion/    # Variable expansion and heredoc processing
│   ├── io/           # I/O redirection and heredoc handling
│   ├── parser/       # Command parser and AST builder
│   ├── signals/      # Signal handling
│   ├── tokenizer/    # Lexical analysis
│   └── utils/        # Utility functions
├── lib/              # External libraries (libft)
└── Makefile

Building

Requirements

• GCC or Clang compiler
• GNU Readline library
• Make

Compilation

make
make clean
make fclean
make re

Usage

# Run the shell
./minishell

# Interactive mode
minishell$ ls -la | grep minishell
minishell$ echo "Hello, World!"
minishell$ export MY_VAR=value
minishell$ echo $MY_VAR
minishell$ exit

Example Commands

# Simple commands
minishell$ ls
minishell$ pwd

# Pipes
minishell$ ls -la | grep txt | wc -l

# Redirections
minishell$ echo "hello" > file.txt
minishell$ cat < file.txt
minishell$ echo "world" >> file.txt

# Heredocs
minishell$ cat << EOF
> This is a heredoc
> Multiple lines supported
> EOF

# Environment variables
minishell$ echo $HOME
minishell$ echo $?
minishell$ export PATH=$PATH:/new/path

Architecture

Execution Flow

1. Readline - Read user input with history support
2. Tokenizer - Break input into tokens (words, operators)
3. Parser - Build Abstract Syntax Tree (AST) from tokens
4. Expansion - Expand variables and process heredocs
5. Executor - Execute commands, handle pipes and redirections

Memory Management

The shell uses a garbage collector (t_gc) to manage memory during command execution, ensuring proper cleanup after each command.

Signal Handling

• Ctrl+C (SIGINT): Interrupt current command, display new prompt
• Ctrl+\ (SIGQUIT): Ignored in interactive mode
• Ctrl+D (EOF): Exit the shell

Known Limitations

This is an educational implementation with some limitations compared to full bash:

• No support for &&, ||, or ; operators
• No wildcards/globbing (*, ?)
• No command substitution ($(command) or `command`)
• Limited history expansion features

License

This project is part of the 42 School curriculum. See the 42 School guidelines for usage terms.