Muski Shell

A lightweight, custom shell implementation in C with essential command-line utilities. Built from scratch to understand how shells work at a low level using system calls and process management.

🚀 Features

Built-in Commands

• cd [directory] - Change directory with home directory support (cd ~)
• exit - Exit the shell gracefully

External Commands

• echo [text] - Print text to standard output
• ls [directory] - List files and directories with color coding
  • 🔵 Blue for directories
  • 🟢 Green for files
• clear - Clear the terminal screen
• touch [filename] - Create empty files
• edit [filename] - Simple text editor with save/quit functionality

Core Shell Features

• Real-time current working directory display
• Command parsing and tokenization
• Process management with fork() and execv()
• Error handling for invalid commands and system calls
• Custom prompt: Muski-shell: /current/path>

📦 Build Instructions

Prerequisites

• GCC compiler
• Linux/Unix environment
• Standard C library

Compilation Steps

1. Clone or navigate to the project directory:

   cd /path/to/Muski-shell

2. Create the build directory:

   mkdir -p build

3. Compile all command utilities:

   gcc commands/echo.c -o build/echo
   gcc commands/ls.c -o build/ls
   gcc commands/clear.c -o build/clear
   gcc commands/touch.c -o build/touch
   gcc commands/edit.c -o build/edit

4. Compile the main shell:

   gcc main.c -o terminal

5. Run the shell:

   ./terminal

Quick Build Script

Create a build.sh file for easier compilation:

#!/bin/bash
mkdir -p build
gcc commands/echo.c -o build/echo
gcc commands/ls.c -o build/ls
gcc commands/clear.c -o build/clear
gcc commands/touch.c -o build/touch
gcc commands/edit.c -o build/edit
gcc main.c -o terminal
echo "Build complete! Run ./terminal to start."

Then run: chmod +x build.sh && ./build.sh

📖 Command Reference

Basic Commands

# Display text
echo Hello, World!

# List files in current directory
ls

# List files in specific directory
ls /home/user

# Change directory
cd /path/to/directory
cd ~  # Go to home directory
cd .. # Go to parent directory

# Create empty file
touch myfile.txt

# Clear screen
clear

# Exit shell
exit

Text Editor (edit)

# Open or create a file
edit myfile.txt

# Editor commands:
:w      # Save file
:q      # Quit without saving
:wq     # Save and quit
:l      # List all lines with numbers
:d5     # Delete line 5

📂 Project Structure

Muski-shell/
├── main.c              # Main shell loop and built-in commands
├── commands/           # External command implementations
│   ├── echo.c         # Echo command
│   ├── ls.c           # List files with colors
│   ├── clear.c        # Clear terminal
│   ├── touch.c        # Create files
│   └── edit.c         # Simple text editor
├── build/             # Compiled binaries (gitignored)
├── terminal           # Main shell executable (gitignored)
├── .gitignore         # Git ignore rules
└── README.md          # This file

💡 Usage Examples

Example Session

Muski-shell: /home/user/projects>
ls
file1.txt    folder1    script.sh    README.md

Muski-shell: /home/user/projects>
echo Creating a new file...
Creating a new file...

Muski-shell: /home/user/projects>
touch notes.txt

Muski-shell: /home/user/projects>
edit notes.txt
=== Simple Text Editor ===
edit> This is my first line
Added line 1
edit> This is my second line
Added line 2
edit> :wq
File saved and quit (2 lines)

Muski-shell: /home/user/projects>
cd ~

Muski-shell: /home/user>
exit

🔮 Future Ideas

Planned Features

1. I/O Redirection (High Priority)

• Output redirection: ls > output.txt
• Input redirection: cat < input.txt
• Append mode: echo "text" >> file.txt
• Error redirection: command 2> error.log

2. Pipes (High Priority)

• Chain commands: ls | grep .txt
• Multiple pipes: cat file.txt | grep pattern | wc -l

3. Background Processes

• Run processes in background: command &
• Job control: jobs, fg, bg
• Process status display

4. Command History

• Arrow key navigation (↑/↓)
• history command to view past commands
• !n to execute command n from history
• Persistent history across sessions

5. Tab Completion

• Auto-complete file and directory names
• Command name completion
• Path completion with multiple suggestions

6. Advanced Text Editor

• Insert/replace mode switching
• Line editing (insert at position)
• Search and replace functionality
• Undo/redo capability
• Syntax highlighting
• Multiple buffer support

7. Signal Handling

• Ctrl+C to interrupt current process
• Ctrl+Z to suspend processes
• Proper cleanup on signals

🛠️ Technical Details

System Calls Used

• fork() - Create child processes
• execv() - Execute external commands
• wait() - Wait for child process completion
• chdir() - Change working directory
• getcwd() - Get current working directory
• opendir(), readdir(), closedir() - Directory operations
• stat() - File information

Key Concepts

• Process Management: Parent-child process relationships
• File Descriptors: Standard input/output/error
• Path Resolution: Finding executables in custom paths
• String Parsing: Tokenizing command-line input
• Error Handling: Proper cleanup and error messages

🐛 Known Limitations

• No pipe support yet
• No I/O redirection
• No signal handling (Ctrl+C kills entire shell)
• Limited command history
• No tab completion
• Commands must be in /build directory

🤝 Contributing

This is a learning project! Feel free to:

• Add new commands
• Implement planned features
• Fix bugs
• Improve documentation

📝 License

This project is for educational purposes. Feel free to use and modify.

👨‍💻 Author

Built with ❤️ to learn systems programming and shell internals.

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Note: This shell is a learning project and not intended for production use. For daily work, use bash, zsh, or other mature shells.