Minishell

Minishell is a simplified UNIX shell developed as part of the Hive Helsinki curriculum.
It is a from-scratch implementation of core shell features like command execution,
process handling, input/output redirection, pipes, and signal handling.

📌 What This Project Demonstrates

This project is an exercise in system programming in C.
It showcases key low-level programming concepts, including:

• System calls: fork(), execve(), pipe(), dup2(), waitpid(), etc.
• Process control: Managing child processes, job control.
• Memory management: Avoiding leaks, handling dynamic allocations.
• File descriptors & redirections: Implementing <, >, <<, >>.
• Signal handling: Handling SIGINT (Ctrl+C), SIGQUIT (Ctrl+\).
• Environment management: Handling $PATH, variable expansion.

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👥 Collaborators

• Markus Laaksonen
• Lionel

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🚀 Features

✅ Execute commands like Bash
✅ Built-in commands: cd, echo, pwd, export, unset, env, exit
✅ Pipes (|): Chain multiple commands
✅ Input/output redirection: <, >, <<, >>
✅ Signal handling: Handle Ctrl-C, Ctrl-D, Ctrl-\
✅ Environment variables: $PATH, $HOME, $?, etc.
✅ Command history (via readline)

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⚠️ Compatibility

✅ Currently supports: Linux
❌ MacOS support is currently broken due to Readline differences.

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🛠 Installation

1. Clone the repository:

   $ git clone https://github.com/liocle/minishell.git
   $ cd minishell

2. Install dependencies:

   $ sudo apt update && sudo apt install libreadline-dev libncurses-dev

3. Compile the project:

   $ make

4. Run Minishell:

   $ ./minishell

📌 Usage Examples

$ ls -l              # List files 
$ echo Hello World   # Print "Hello World"
$ export PAGER=less  # Set an environment variable
$ cd /home/user      # Change directory
$ cat file | grep foo > output.txt  # Use pipes and redirections

💡 What I Learned

This project deepened my understanding of C and UNIX internals, including:

• Process creation & management (fork(), execve(), waitpid())
• File descriptors (open(), close(), dup2())
• Signal handling (SIGINT, SIGQUIT, signal(), sigaction())
• Memory management (malloc(), free(), detecting leaks)
• Inter-process communication (pipe())
• I now have hands-on experience writing system-level C code and working with complex debugging scenarios.

💡 Real-World Applications

✅ Real-world C experience → This project mimics real shell behavior, reinforcing key system programming skills.
✅ System calls knowledge → I now understand how UNIX shells execute commands, handle pipes, and manage processes.
✅ Debugging skills → Learned to debug memory leaks, segmentation faults.
✅ Handling edge cases → Unclosed quotes, invalid input, redirections, $? expansion, etc.

🛠 Implemented Built-in Commands

• cd
• echo -n
• pwd
• export
• unset
• env
• exit

Minishell also executes any external command found in $PATH.

🤝 Contributing

Want to improve Minishell? Follow these steps:

1. Fork the repository.
2. Create a feature branch.
3. Commit your changes.
4. Submit a pull request.

📜 License

This project was built as part of the Hive Helsinki curriculum and is intended for educational purposes.