Minishell Project

Index

• Minishell Project
  • Index
  • Introduction
  • Project Overview
    • Key Features:
  • Technologies Used
  • Project Difficulty
  • Implementation Details
    • Shell Behavior
    • Built-in Commands
    • Redirection and Piping
  • Usage Guide
    • Installation
    • Running the Shell
    • Exiting the Shell
  • Available Commands

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Introduction

Welcome to the Minishell project! This project involves creating a simple shell similar to Bash. Through this project, you will gain deep insights into how processes and file descriptors work in Unix-based systems. Minishell is designed to offer a journey back to the origins of command-line interfaces, allowing you to explore fundamental IT concepts and the challenges faced by developers before the advent of graphical user interfaces.

Project Overview

The goal of this project is to build a functional shell that can interpret and execute user commands in a Unix-like environment. The shell will support basic features such as executing commands, handling input/output redirection, managing pipes, and expanding environment variables. Additionally, the project involves implementing several built-in commands to simulate the behavior of a standard shell.

Key Features:

• Command execution based on the PATH environment variable.
• Input/output redirection and piping.
• Built-in commands such as echo, cd, pwd, export, unset, env, and exit.
• Signal handling for interactive command-line behavior (e.g., ctrl-C, ctrl-D).

Technologies Used

This project is implemented in C and adheres to strict coding norms to ensure reliability and maintainability. Key technologies and libraries include:

• readline for command-line input handling.
• Standard C libraries for memory management, file I/O, and process control.
• Libft, a custom C library, is used for various utility functions.

Project Difficulty

The Minishell project is considered to be of moderate to high difficulty. It requires a solid understanding of process management, memory handling, and Unix system calls. Additionally, careful attention to detail is needed to avoid issues like memory leaks and segmentation faults. The project also demands strict adherence to coding standards and efficient management of resources such as file descriptors and environment variables.

Implementation Details

Shell Behavior

The shell displays a prompt and waits for user input. It processes the input to:

• Parse and interpret commands.
• Handle quoted strings and special characters.
• Implement redirections and pipelines.

Built-in Commands

The shell includes several built-in commands that are executed internally rather than by spawning new processes. These include:

• echo: Outputs text to the terminal with an optional -n flag.
• cd: Changes the current directory.
• pwd: Prints the current working directory.
• export: Sets environment variables.
• unset: Removes environment variables.
• env: Displays the current environment variables.
• exit: Exits the shell.

Redirection and Piping

The shell supports standard input and output redirection using >, <, >>, and <<. Redirection allows commands to read input from a file or write output to a file. Piping allows the output of one command to be used as the input to another, using the pipe | operator.

Usage Guide

Installation

1. Clone the repository to your local machine.
2. Navigate to the project directory.
3. Compile the project using the following command:

make

This will generate the minishell executable.

Running the Shell

To start the shell, simply run the following command:

./minishell

You will be greeted with a prompt where you can start entering commands.

Exiting the Shell

To exit the shell, use the exit command or press ctrl-D.

Available Commands

The following built-in commands are available in Minishell:

• echo: Prints text to the terminal. Usage: echo [-n] [string ...]
• cd: Changes the current directory. Usage: cd [directory]
• pwd: Displays the current working directory.
• export: Sets environment variables. Usage: export [variable=value]
• unset: Removes environment variables. Usage: unset [variable]
• env: Displays all environment variables.
• exit: Exits the shell. Usage: exit [status]