Custom Unix Shell

A fully functional Unix shell implemented in C, supporting process management, job control, signal handling, redirection, piping, and command history.

Features 🚀

• Process Creation & Execution (fork(), exec(), wait())
• Foreground & Background Process Management (& support)
• Signal Handling (SIGCHLD, SIGINT, SIGTSTP)
• Built-in Commands (cd, exit)
• Input & Output Redirection (<, >)
• Piping (|)
• Command History (using readline library)
• Tab Auto-Completion (via readline)

Installation & Usage 🔧

Clone the Repository

git clone https://github.com/your-username/custom-shell.git
cd custom-shell

Compile the Shell

gcc -o custom_shell custom_shell.c -lreadline

Run the Shell

./custom_shell

Usage Examples

✅ Running Basic Commands

custom-shell$ ls -l
custom-shell$ echo "Hello, Unix Shell!"

✅ Background Execution

custom-shell$ sleep 10 &
[Background Job] PID: 12345

✅ Job Control (Foreground & Background)

custom-shell$ fg 12345   # Brings process 12345 to foreground
custom-shell$ bg 12345   # Resumes process 12345 in background

✅ Input & Output Redirection

custom-shell$ cat < input.txt
custom-shell$ ls > output.txt

✅ Piping

custom-shell$ ls | grep ".c" | wc -l

✅ Built-in Commands

custom-shell$ cd /home/user
custom-shell$ exit

✅ Command History & Auto-Completion

- Use Arrow keys (Up/Down) to browse history.
- Type part of a command and press Tab for auto-completion.

Implementation Details

1️⃣ Process Creation & Execution

• Uses fork() to create child processes.
• Executes commands using execvp().
• Waits for foreground processes using waitpid().

2️⃣ Signal Handling

• SIGINT (Ctrl+C): Terminates foreground processes.
• SIGTSTP (Ctrl+Z): Sends process to background.
• SIGCHLD: Handles background process termination.

3️⃣ Redirection (<, >)

• Redirects standard input/output using dup2() and open().

4️⃣ Piping (|)

• Implements inter-process communication via pipe().
• Spawns multiple child processes and connects input/output streams.

5️⃣ Built-in Commands

• cd (change directory)
• exit (terminate shell)

License 📜

This project is licensed under the MIT License.

👨‍💻 Author

Srinath Duvvuri 📧 duvvurisrinath@gmail.com