Simple Shell

Overview

Simple Shell is a basic UNIX command line interpreter developed as a collaborative project. This project involves implementing essential features of a shell in C, adhering to the requirements and constraints typical of a UNIX environment.

Contributors

• Name: Paschal Ugwu
• Email: ugwupaschal@gmail.com

Table of Contents

• Introduction
• Features
• Usage
• Compilation
• Tasks
  • Task 0: Betty would be proud
  • Task 1: Simple shell 0.1
  • Task 2: Simple shell 0.2
  • Task 3: Simple shell 0.3
  • Task 4: Simple shell 0.4
  • Task 5: Simple shell 1.0
  • Advanced Tasks
• Resources
• Testing
• Acknowledgments

Introduction

This project implements a simple UNIX command interpreter, commonly known as a shell. It covers fundamental aspects of shell functionality, including command execution, environment management, and built-in commands.

Features

• Interactive Mode: Prompts the user for commands and executes them.
• Non-Interactive Mode: Executes commands from a file or standard input.
• Command Execution: Executes commands located in directories specified by the PATH environment variable.
• Built-in Commands: Supports built-in commands like exit and env.

Usage

Interactive Mode

$ ./hsh
($) /bin/ls
($) exit

Non-Interactive Mode

$ echo "/bin/ls" | ./hsh
$ cat commands.txt | ./hsh

Compilation

Compile the shell with:

gcc -Wall -Werror -Wextra -pedantic -std=gnu89 *.c -o hsh

Ensure to use gcc with the provided options to meet project requirements.

Tasks

Task 0: Betty would be proud

• Objective: Ensure all code adheres to the Betty style guide.
• Implementation: Verify code style using betty-style.pl and betty-doc.pl.

Task 1: Simple shell 0.1

• Objective: Implement a basic shell that:
  • Displays a prompt and waits for user input.
  • Executes simple commands without arguments.
  • Handles "end of file" (Ctrl+D) and errors.
• Limitations: No support for advanced features like pipes, redirections, or multiple commands.

Task 2: Simple shell 0.2

• Objective: Extend the shell to handle command lines with arguments.
• Enhancements: Parse and execute commands with arguments.

Task 3: Simple shell 0.3

• Objective: Integrate PATH handling.
• Enhancements: Search for commands in directories specified by the PATH environment variable.

Task 4: Simple shell 0.4

• Objective: Implement the exit built-in command.
• Enhancements: Support exiting the shell using the exit command.

Task 5: Simple shell 1.0

• Objective: Implement the env built-in command.
• Enhancements: Display the current environment variables.

Advanced Tasks

1. Simple shell 0.1.1: Implement a custom getline function using a buffer.
2. Simple shell 0.2.1: Implement custom tokenization without strtok.
3. Simple shell 0.4.1: Handle arguments for the exit built-in command.
4. setenv, unsetenv: Implement setenv and unsetenv built-ins for environment variable management.
5. cd: Implement the cd built-in command.
6. ;: Handle command separator ;.
7. && and ||: Implement logical operators && and ||.

Resources

• Unix shell: Wikipedia
• Thompson shell: Wikipedia
• Ken Thompson: Wikipedia
• Shell Programming Guide: Everything you need to know to start coding your own shell

Testing

Test the shell in both interactive and non-interactive modes. Ensure it handles common edge cases and adheres to expected behavior as outlined in the tasks.

Acknowledgments

This project was developed as part of the ALX Software Engineering curriculum. Special thanks to the ALX community for their guidance and support.