🐚 Minishell

As beautiful as a shell — 42 Network project

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📖 About

Minishell is a 42 school project that challenges you to create your own simplified version of bash. It involves building a fully functional shell from scratch in C, capable of parsing user input, managing processes, and executing commands — just like a real terminal.

This project is a deep dive into how shells work under the hood: lexing, parsing, process creation, file descriptor management, and signal handling.

✨ Features

• 🔍 Command Execution — Run any system binary via PATH resolution or absolute paths
• 🔀 Pipes — Chain commands with | (e.g., ls -la | grep .c | wc -l)
• 📁 Redirections — Input <, output >, append >>, and heredoc <<
• 💲 Environment Variables — Expand $VAR and $? (last exit status)
• 🏠 Built-in Commands:
  • echo (with -n flag)
  • cd (relative and absolute paths)
  • pwd
  • export / unset
  • env
  • exit
• 🔔 Signal Handling — Ctrl+C, Ctrl+D, Ctrl+\ behave like in bash
• 📝 Command History — Navigate previous commands with arrow keys
• 🔗 Quote Handling — Single ' and double " quotes with proper parsing

🚀 Getting Started

Prerequisites

• GCC compiler
• Make
• readline library (sudo apt install libreadline-dev on Ubuntu)
• A UNIX-based OS (Linux / macOS)

Build

git clone https://github.com/JMADIL/MINISHELL.git
cd MINISHELL
make

Usage

./minishell

You'll be greeted with a prompt where you can type commands just like in bash:

minishell$ echo "Hello World"
Hello World
minishell$ ls -la | grep .c | wc -l
3
minishell$ export MY_VAR="42"
minishell$ echo $MY_VAR
42
minishell$ exit

📂 Project Structure

MINISHELL/
├── Makefile            # Build system
├── minishell.c         # Entry point & main loop (prompt, read, execute)
├── minishell.h         # Header with structs, prototypes & includes
├── cleaning.c          # Memory cleanup & free functions
├── pars/               # Parsing module (lexer, tokenizer, AST)
└── exec/               # Execution module (builtins, pipes, redirections)

🏗️ Architecture

┌─────────────────────────────────────────────────────┐
│                     MINISHELL                       │
├─────────────────────────────────────────────────────┤
│                                                     │
│   Input ──► Lexer ──► Parser ──► Executor ──► Output│
│     │                    │            │              │
│  readline()         Token List    fork/execve        │
│                     + AST         + pipes            │
│                                   + redirections     │
│                                                     │
├─────────────────────────────────────────────────────┤
│  Built-ins: echo, cd, pwd, export, unset, env, exit │
└─────────────────────────────────────────────────────┘

🔑 Key Concepts Learned

Concept	Description
Lexing & Parsing	Tokenizing raw input and building an abstract syntax tree
Process Management	Creating child processes with fork() and execve()
Pipes	Inter-process communication via pipe() and file descriptors
Redirections	Manipulating stdin/stdout with dup2()
Signals	Handling SIGINT, SIGQUIT, SIGTERM in parent and child
Environment	Managing environment variables as a linked list
Memory Management	Preventing leaks with proper cleanup routines

👤 Author

Adil Jamoun — @JMADIL & @ilyasrf

🏫 1337 Coding School (42 Network) — Morocco