🐚💻 Mini Shell using C++

This project implements a custom Unix-like command-line shell built entirely in C++.
It supports command execution, pipelines, I/O redirection, background job control, and several built-in commands — providing a hands-on exploration of how real Linux shells work internally.

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📂 Files

✅ myshell.cpp

• Main source file of the project.
• Implements core shell functionalities:
  • Command parsing and execution using fork(), execvp(), and waitpid().
  • Supports input/output redirection using dup2() and open().
  • Handles pipelines via pipe().
  • Manages background and foreground processes.
  • Integrates built-in commands like:
    • cd, exit, history, jobs, fg, bg, export.

✅ Built-in Commands Overview

Command	Usage	Description
cd	cd [dir]	Change directory (default: HOME).
exit	exit	Exit the shell.
history	history	Show command history.
jobs	jobs	List running background jobs.
fg	fg [job_id]	Bring job to foreground.
bg	bg [job_id]	Resume stopped job in background.
export	export VAR=value	Export environment variable.

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🚀 Features

• Execute any standard Linux commands (ls, cat, grep, etc.)
• Chain commands using pipes (|)
• Perform I/O redirection:
  • < input.txt for input
  • > output.txt for overwrite
  • >> output.txt for append
• Run commands in background using &
• Maintain command history
• Manage jobs, foreground/background tasks
• Implemented using core Linux system calls: fork, execvp, pipe, dup2, and waitpid

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⚙️ Installation

🧰 Prerequisites

• Linux / POSIX environment
• g++ compiler (tested on g++ 11.3.0 or higher)

🧪 Setup

git clone https://github.com/Vraj2309/Mini-Shell.git cd Mini-Shell g++ -std=c++17 -Wall -Wextra -o myshell myshell.cpp ./myshell

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🧠 Example Usage

myshell:/home/user$ ls -l myshell:/home/user$ cat file.txt | grep "example" myshell:/home/user$ sort < input.txt > output.txt myshell:/home/user$ sleep 5 & myshell:/home/user$ jobs myshell:/home/user$ fg 1 myshell:/home/user$ export PATH=/usr/local/bin:$PATH myshell:/home/user$ history

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🧬 Concepts Demonstrated

• Process creation and management (fork, execvp, waitpid)
• Inter-process communication via pipe
• File I/O and descriptor duplication using dup2
• Signal handling for background processes
• Implementation of classic shell features from scratch

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⚡ Design Philosophy

Mini-Shell demonstrates how a basic Unix shell works under the hood — designed as an educational project for students learning Operating Systems, Systems Programming, and Linux internals.

Key challenges include:

• Pipeline chaining through multiple processes.
• Proper file descriptor management.
• Background job handling and signal forwarding.
• Error management without external libraries.

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🛠 Future Enhancements

• Persistent command history file.
• Support for command-line autocompletion.
• Improved quoting/parsing mechanics.
• Additional built-in commands.
• Integration with a Makefile build system.

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📜 License

This project is licensed under the MIT License.
See the LICENSE file for more details.

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👨‍💻 Author

Developed by Vraj Patel

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🧩 “Mini-Shell is a deep-dive experiment into how Linux commands, processes, and pipes truly work behind the scenes.”