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📖 About

Minishell is a small bash-like shell built 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, implemented from scratch with UNIX system calls.

Built in a pair with @juaugry at 42 Paris; I focused on command execution, pipes and redirections.

"As beautiful as a shell." (42 subject)

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✨ 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

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🏗️ 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

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🔧 Shell Pipeline

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

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🚀 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

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🧪 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

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📚 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

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