Mini Unix Shell in C

A lightweight Unix-like shell implemented in C using POSIX system calls. This project demonstrates fundamental operating system concepts such as process creation, inter-process communication, file descriptor management, and signal handling.

✨ Features

• Execute external commands using fork() and execvp()
• Built-in commands:
  • cd
  • pwd
  • help
  • exit
• Input redirection (<)
• Output redirection (>)
• Append output redirection (>>)
• Command pipelines (|)
• Background process execution (&)
• Signal handling (Ctrl+C / SIGINT)
• Modular command parsing and execution

🛠 Technologies Used

• C
• POSIX System Calls
• GCC
• Linux

📚 Operating System Concepts Demonstrated

• Process Creation (fork)
• Program Execution (execvp)
• Parent-Child Process Synchronization (wait, waitpid)
• Pipes and Inter-Process Communication (pipe)
• File Descriptor Duplication (dup2)
• File Operations (open, close)
• Signal Handling (sigaction)
• Input/Output Redirection

🚀 Building the Project

Compile using GCC:

gcc shell.c -o shell

▶️ Running

./shell

Example prompt:

Madhan-Shell :>

💻 Example Commands

Execute a command

ls

Change directory

cd Documents

Print current directory

pwd

Input redirection

sort < input.txt

Output redirection

ls > files.txt

Append output

echo Hello >> output.txt

Pipeline

cat file.txt | grep hello | wc -l

Background process

sleep 10 &

📁 Project Structure

.
├── shell.c
└── README.md

📌 Future Enhancements

• Command history
• Tab completion
• Environment variable expansion
• Wildcard (*) support
• Job control (jobs, fg, bg)
• Command chaining (&&, ||, ;)
• Quote-aware command parsing

🎯 Learning Outcomes

This project provided hands-on experience with:

• Process management in Unix/Linux
• Inter-process communication
• Shell command parsing
• File descriptor manipulation
• Signal handling
• POSIX programming

📄 License

This project is open source and available under the MIT License.