Simple Interactive SHell (sish)

👩‍💻 Overview

This project is a basic Linux shell implementation called sish. It supports:

• Executing system commands
• Built-in commands: cd, exit, history
• A command history buffer (last 100 commands)
• Multi-process Unix-style pipes (|)

📁 Files

• sish.c: Main source code
• hist100: Input file to test if only 100 commands are stored in history (from stdin redirection)

⚙️ How to Compile and Run

Compile (on a Linux machine):

gcc sish.c -o sish -Wall -Werror -std=gnu99

🔨 Features

Command Execution

• Prompts with: sish>
• Tokenizes input and executes basic Linux commands (e.g., ls, pwd, echo)
• Uses fork() + execvp()

Built-in Commands

Command	Description
exit	Exit the shell
cd [dir]	Change directory using chdir()
history	Show the last 100 commands
history -c	Clear all command history
history [n]	Execute command at offset n

Pipe Support

• Executes commands with pipes like ls | wc
• Supports multi-level pipes like cat hist100 | grep cat | wc

🧪 Test Cases

Please refer to the file testcases.txt for all test case inputs and expected behaviors.

Ensure you test:

• Basic command execution (ls, pwd, echo, etc.)
• Built-in commands (cd, exit, history)
• History overflow and offset execution
• Piped commands (ls | wc, cat hist100 | grep ... | wc)

You can also run:

./sish < hist100