---

📖 About

Minishell is a lightweight POSIX-compliant shell built entirely in C as part of the 42 School curriculum. It replicates core behaviors of bash, including command execution, pipes, redirections, environment variable expansion, and signal handling — all implemented from scratch using raw system calls.

"As beautiful as a shell." — 42 Subject

---

✨ Features

Category	Details
Prompt	Interactive prompt with command history (readline)
Builtins	echo, cd, pwd, export, unset, env, exit
Execution	Searches and launches executables via PATH or absolute/relative paths
Pipes	Full pipe chain support (`cmd1
Redirections	Input <, Output >, Append >>, Here-document <<
Env Variables	Expansion of $VAR and $? (last exit status)
Quotes	Single quotes ' ' (literal) and double quotes " " (with expansion)
Signals	Ctrl+C, Ctrl+D, Ctrl+\ behave like in bash

---

🏗️ Architecture

Minishell/
├── includes/
│   └── minishell.h          # Main header — structs, prototypes, macros
├── srcs/
│   ├── builtins/            # Built-in command implementations
│   │   ├── cd.c
│   │   ├── echo.c / echo_utils.c
│   │   ├── env.c
│   │   ├── exit.c / exit_utils.c
│   │   ├── export.c / export_utils.c
│   │   ├── pwd.c
│   │   └── unset.c
│   ├── lexer.c / lexer_utils.c        # Tokenization
│   ├── parser.c                        # AST construction
│   ├── make_token.c / token_utils.c    # Token management
│   ├── expand.c / expand_utils.c       # Variable expansion
│   ├── no_expand_quote.c / no_expand_utils.c  # Quote handling
│   ├── exec.c / exec_utils.c          # Command execution & fork
│   ├── pipe.c                          # Pipe management
│   ├── change_fd.c                     # File descriptor redirections
│   ├── init_cmd.c / cmd_utils.c        # Command struct init
│   ├── init_data.c / init_data_utils.c # Shell data initialization
│   ├── init_global.c                   # Global state
│   ├── signal.c                        # Signal handlers
│   ├── main.c / main_utils.c          # Entry point & REPL loop
│   ├── add_link.c / new_link.c        # Linked list operations
│   └── free_data.c                     # Memory cleanup
├── libft/                   # Custom C standard library (42)
└── Makefile                 # Build system

---

🔧 Shell Pipeline

Input ──▶ Lexer ──▶ Parser ──▶ Expander ──▶ Executor
  │         │         │           │            │
  │      Tokenize   Build      Resolve      Fork &
  │      input      command    $VARS &      execve()
  │      string     tree       quotes       with pipes
  │                                         & redirects
  ▼
Prompt (readline)

---

🚀 Getting Started

Prerequisites

• GCC or Clang
• Make
• readline library (libreadline-dev on Debian/Ubuntu)

Build & Run

# Clone the repository
git clone https://github.com/Wesper-Dev/Minishell.git
cd Minishell

# Compile
make

# Launch
./minishell

Usage Examples

minishell$ echo "Hello, World!"
Hello, World!

minishell$ ls -la | grep ".c" | wc -l
24

minishell$ cat < input.txt > output.txt

minishell$ export USER=Arnaud && echo $USER
Arnaud

minishell$ << EOF cat
> line 1
> line 2
> EOF
line 1
line 2

---

🧪 Tested Against

• Bash reference behavior for all builtins
• Edge cases: empty commands, unclosed quotes, multiple pipes, nested redirections
• Signal handling in parent and child processes
• Memory leaks checked with Valgrind

---

📚 Key Concepts Learned

• Process creation — fork(), execve(), waitpid()
• Inter-process communication — pipe(), dup2()
• File descriptor management — redirections, here-documents
• Lexing & Parsing — tokenization, recursive descent
• Signal handling — sigaction(), terminal control
• Memory management — custom allocators, leak-free design

---