Minishell

As beautiful as a shell

Introduction

Minishell is a project from the 42 curriculum that involves creating a simple UNIX shell. The goal is to understand processes, file descriptors, and how a shell interprets and executes commands.

This project was successfully completed with a perfect score of 125/100, including the mandatory and bonus parts.

Features

Mandatory Features

• A prompt that waits for user input.
• Command execution with support for:
  • Relative and absolute paths.
  • The PATH environment variable.
• Handling of:
  • Single (') and double (") quotes.
  • Redirections:
    • < (input redirection)
    • > (output redirection)
    • << (here-document)
    • >> (append output redirection)
  • Pipes (|): connecting multiple commands.
  • Environment variables ($VAR).
  • The special variable $? (exit status of the last command).
  • Signals:
    • Ctrl+C (interrupts current command and displays a new prompt).
    • Ctrl+D (exits the shell).
    • Ctrl+\ (ignored).
• Built-in commands:
  • echo (with -n option)
  • cd (with absolute or relative paths)
  • pwd (prints the working directory)
  • export (sets environment variables)
  • unset (removes environment variables)
  • env (displays the environment variables)
  • exit (exits the shell)

Bonus Features

• Logical operators && and ||, with support for parentheses to manage priorities.
• Wildcard * expansion for matching files in the current directory.

Implementation Details

To implement the shell, we chose to understand and implement an Abstract Syntax Tree (AST) as close as possible to the one used in the original Bash, to fully fulfill the spirit of the project. This approach ensures correct parsing and execution of complex command structures while maintaining scalability and efficiency.

Installation

1. Clone the repository:

   git clone <repository_url>
   cd minishell

2. Compile the project:

   make

3. Run the shell:

   ./minishell

Usage

• Type commands as you would in Bash.
• Use redirections, pipes, and environment variables.
• Exit the shell using exit or Ctrl+D.

Compilation

• The project follows the 42 Norm.
• Uses Makefile with the following rules:
  • make: Compiles the project.
  • make clean: Removes object files.
  • make fclean: Removes compiled binaries.
  • make re: Recompiles the project.
  • make bonus: Compiles the bonus features.

External Functions Used

• readline, add_history
• Standard system calls: fork, execve, pipe, dup2, waitpid, etc.

Author

• tarrapunchia (fzucconi@student.42firenze.it)

This project was an invaluable learning experience in process handling, memory management, parsing, data structures...
In summary: in shell behavior (which i loved :).

Contributors

This project is part of the 42 School Network (42Luiss Firenze) and was done together with three other amazing programmers: Ulisse Colla (ucolla), Stefano Montuori (smontuor) and Tommaso Picchio (tpicchio).