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Minishell_42

Minishell_42 is a simplified shell program designed to mimic the behavior of a UNIX shell. It is a part of the 42 Network curriculum and is meant to help students learn about the core functionalities of shell commands, environment variables, and process management. The project involves implementing a shell from scratch, providing fundamental shell features such as command parsing, file redirection, environment variable expansion, command execution, and more.

Features

  • Command Parsing: The shell parses user input and interprets commands.
  • Environment Variables: Support for handling environment variables like $HOME, $PATH, etc.
  • Process Management: Executes commands in a separate process and supports piping and redirection.
  • Built-in Commands: Implements common shell built-ins like cd, echo, exit, pwd, export, unset, and env.
  • File Redirection: Handles file redirection for input/output, including >, >>, and <.
  • Piping: Supports piping between commands using |.
  • Herodoc: Implements heredoc functionality to handle multi-line input redirection.

Table of Contents

  1. Project Structure
  2. Compilation & Installation
  3. Usage
  4. Key Components
  5. Built-in Commands
  6. Parser
  7. Execution
  8. Memory Management
  9. Error Handling
  10. Contributing

Project Structure

This project is organized into multiple directories and files, each serving a specific purpose:

Main Directories:

  • src/: Contains the core functionality of the shell program.
  • lib/: Includes helper functions used throughout the project, such as string manipulation, memory management, and utility functions.
  • memory/: Implements memory management utilities for efficient handling of dynamic memory.
  • components/: A collection of smaller submodules, each dedicated to specific parts of the shell (like parsing, lexer, execution).
  • parser/: Responsible for breaking down the input commands into tokens and interpreting them.
  • prompt/: Handles user input and displays the shell prompt.
  • lexer/: Implements the lexical analyzer, converting raw input into structured tokens.
  • expander/: Expands environment variables and handles command substitution.
  • herdoc/: Handles heredoc functionality.
  • execution/: Executes commands and manages processes.
  • env/: Manages environment variables.
  • builtin/: Implements built-in shell commands like cd, echo, exit, etc.
  • execute/: Handles the execution flow, including file redirection and pipes.

Key Files:

  • Makefile: Automates the build process, defining how to compile and link the project.
  • minishell.h: The header file containing declarations for the main program functions.
  • execution.h: Declares functions related to command execution.
  • parser.h: Defines functions for parsing user input and handling syntax.

Notable Functions & Files:

  • lib/ft_*.c: Functions that provide basic utilities such as string manipulation (e.g., ft_atoi.c, ft_strncpy.c, ft_strlen.c, etc.).
  • parser/parser.c: Main file responsible for parsing the input.
  • lexer/lexer.c: Handles lexical analysis of user input.
  • expander/expander.c: Expands variables and processes them before execution.
  • execution/execution.c: Executes commands and processes.
  • builtin/builtin.c: Handles built-in commands (e.g., echo, pwd, cd, etc.).

Compilation & Installation

Requirements:

  • C Compiler (e.g., GCC or Clang)
  • Make (to build the project)
  • Unix-like system (Linux/macOS)

To Compile:

  1. Clone the repository:
git clone https://github.com/iaceene/Minishell_42.git
cd Minishell_42
  1. Build the project using Makefile:
make
  1. To clean the build files:
make clean
  1. To remove all generated files (including binaries):
make fclean
  1. To recompile everything:
make re

Running the Program:

After compiling the project, you can run the shell program with:

./minishell

This will start an interactive shell where you can enter commands.

Usage

Once the shell is running, you can type Unix commands, and it will execute them just like any other shell. Here are some basic features:

  • Command Execution: You can run programs by typing their name (e.g., ls, pwd).

  • Piping: You can chain commands using pipes (|).

    echo "hello" | tr "a-z" "A-Z"

  • Redirection: Input and output redirection works with >, >>, and <.

    echo "Hello" > output.txt
cat < output.txt

  • Built-in Commands: These commands are built into the shell and don’t require external binaries:

    • cd: Change directory.
    • echo: Print text to standard output.
    • exit: Exit the shell.
    • pwd: Print working directory.
    • export: Set environment variables.
    • unset: Remove environment variables.
    • env: Print all environment variables.

Examples:

$ ./minishell
$ echo "Hello World"
Hello World
$ ls
src  lib  memory  components  parser  prompt  lexer  expander  execution  env  builtin
$ cd src
$ ./minishell
$ echo $PWD
/home/user/minishell/src

Key Components

1. Parser

The parser takes user input and splits it into tokens (commands, arguments, and operators). It checks for valid syntax and prepares the data for execution.

2. Lexer

The lexer breaks down the input string into tokens such as words, operators, and symbols. It plays a crucial role in interpreting the user’s intentions.

3. Expander

The expander is responsible for replacing variables in the commands, such as $PATH or $HOME, with their actual values from the environment.

4. Execution

The execution component is responsible for forking new processes, redirecting input/output, handling pipes, and executing commands. It uses system calls like execve() and fork().

5. Memory Management

Efficient memory management is implemented using custom memory tracking functions to avoid leaks. Dynamic memory allocation is handled manually.

Built-in Commands

The following built-in commands are implemented:

  • cd: Changes the current directory.
  • echo: Prints a message to the standard output.
  • exit: Exits the shell.
  • pwd: Prints the current working directory.
  • export: Sets environment variables.
  • unset: Removes environment variables.
  • env: Lists all environment variables.

Example:

$ cd /home/user/projects
$ pwd
/home/user/projects

Error Handling

The shell ensures that errors are caught at every stage:

  • Syntax Errors: If the user inputs a command with invalid syntax, an error message is displayed.
  • Command Not Found: If a command doesn’t exist or is incorrectly typed, the shell will print an error message.
  • Memory Errors: If memory allocation fails, the program gracefully exits with an error message.

Contributing

If you'd like to contribute to Minishell_42, feel free to fork the repository and submit a pull request. Please make sure to:

  • Follow the coding standards used throughout the project.
  • Provide clear and concise commit messages.
  • Write tests where applicable.

License

This project is licensed under the MIT License - see the LICENSE file for details.