🐚 UNIX Shell Project

A custom UNIX shell implementation built from scratch in C as part of BRACU CSE321 (Operating Systems) Lab.

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📋 Table of Contents

• Features
• Getting Started
• Usage
• Built-in Commands
• Team Members
• Contributions

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✨ Features

Feature	Description
Command Prompt	Interactive shell prompt (UNIX Shell >) for user input
Command Execution	Parse and execute system commands using fork() and exec()
Multiple Commands	Execute multiple commands inline using semicolon (;) separator
Logical AND	Sequential command execution with && (stops on failure)
Input Redirection	Redirect input from files using < operator
Output Redirection	Redirect output to files using > (overwrite) or >> (append)
Piping	Chain commands with | for unlimited pipe operations
Signal Handling	Graceful CTRL+C handling without shell termination
Command History	Maintains history of last 20 executed commands

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🚀 Getting Started

Prerequisites

• GCC compiler
• Linux/Unix environment (or WSL on Windows)

Compilation

gcc -o shell "UNIX Shell.c"

Running the Shell

./shell

Or use the provided script:

./run-shell

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💻 Usage

Basic Commands

UNIX Shell > ls -la
UNIX Shell > pwd
UNIX Shell > echo "Hello World"

Multiple Commands with Semicolon

UNIX Shell > ls ; pwd ; whoami

Sequential Execution with AND

UNIX Shell > mkdir test && cd test && touch file.txt

Input/Output Redirection

UNIX Shell > cat < input.txt
UNIX Shell > ls -la > output.txt
UNIX Shell > echo "append this" >> output.txt

Piping Commands

UNIX Shell > ls -la | grep ".c"
UNIX Shell > cat file.txt | sort | uniq
UNIX Shell > ps aux | grep bash | head -5

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📌 Built-in Commands

Command	Description
cd [dir]	Change directory (defaults to $HOME if no argument)
history	Display command history (last 20 commands)
ABOUT	Show program details and contributor information
EXIT	Terminate the shell gracefully

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👥 Team Members

Name	Student ID	GitHub
Al Saihan Tajvi	23301219	—
Farhan Zarif	23301692	@Faustus-Faber
Sadik Mina Dweep	22101837	@sadikmina

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🛠 Contributions

Al Saihan Tajvi

• ✅ Command prompt display and user input handling
• ✅ Command parsing and execution using fork() and exec() system calls
• ✅ Multiple inline commands with semicolon (;) separator
• ✅ Sequential command execution with logical AND (&&)

Farhan Zarif

• ✅ Input redirection (<) using dup() and dup2()
• ✅ Output redirection (>, >>) using dup() and dup2()
• ✅ Command piping (|) supporting unlimited pipes

Sadik Mina Dweep

• ✅ Signal handling (CTRL+C) using signal() and sigaction()
• ✅ Command history maintenance and display

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📄 License

This project was developed for educational purposes as part of the CSE321 Operating Systems course at BRAC University.

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It was an incredible experience collaborating on this project! 🚀