Minishell - a custom-built shell

Table of Contents

1. Overview
2. Features
3. Implementation Details
4. How to use
5. Contributors
6. Acknowledgements

Overview

Minishell is a custom-built shell that replicates essential functionalities of a Unix shell environment. This project serves as a minimalistic shell interpreter with core features to handle command execution, redirections, pipes, environment variable management, and built-in commands. The shell is designed to offer an interactive command-line interface with a focus on simplicity and efficiency.

Features

• Command Prompt: Displays a prompt for user input when waiting for new commands.
• Command History: Maintains a history of previously executed commands.
• Executable Search: Searches for and executes commands based on the PATH variable or a provided relative/absolute path.
• Signal Handling: Utilizes a single global variable to handle signals, ensuring the signal handler does not access the main data structures.
• Quoting:
  • Handles single quotes (') to prevent interpretation of meta-characters within quoted sequences.
  • Handles double quotes (") to prevent interpretation of meta-characters, except for dollar signs ($).
• Redirections:
  • < redirects input.
  • > redirects output.
  • << reads input until a delimiter line is encountered (does not update history).
  • >> appends output to an existing file.
• Pipes: Connects the output of one command to the input of the next command using pipes (|).
• Environment Variables:
  • Expands environment variables ($) to their values.
  • Expands $? to the exit status of the most recently executed foreground pipeline.
• Signal Handling:
  • Ctrl-C displays a new prompt on a new line.
  • Ctrl-D exits the shell.
  • Ctrl-\ does nothing.
• Built-in Commands:
  • echo -n: Outputs text without a trailing newline.
  • cd: Changes the current directory (supports relative and absolute paths).
  • pwd: Prints the current working directory.
  • export: Sets environment variables (no options).
  • unset: Removes environment variables (no options).
  • env: Displays environment variables (no options or arguments).
  • exit: Exits the shell (no options).

Implementation Details

• Signal Handling: Uses a single global variable to capture signal numbers, avoiding direct manipulation of main data structures within the signal handler.
• Memory Management: The readline() function, used for command input, may cause memory leaks, which are not fixed in this implementation. However, the shell’s own code is managed to avoid memory leaks.

How to use

Installation

1. Clone the Repository:

   git clone <repository-url>

2. Compile the Project:

   make

3. Run the Shell:

   ./minishell

Usage

• Command Execution: Type commands at the prompt and press Enter.
• Redirections: Use <, >, <<, and >> to manage input and output redirections.
• Pipes: Connect commands using |.
• Built-ins: Utilize the implemented built-in commands for various shell functionalities.

Contributors

• Alexandru Mitcul
• Andre Silva

Acknowledgements

• The 42 School for providing the project specifications and environment.