Eigen Shell

A lightweight, custom Unix-like shell written in C from scratch to explore OS concepts, system calls, and low-level memory management.

Features & To-Do List

Core Execution & Memory

• Basic REPL loop with standard Fork-Exec-Wait process execution.
• Script execution (batch mode) with support for ignoring # comments.
• Lexical analysis with basic double-quote ("") state handling.
• Robust memory model using deep copy (strdup) and clean garbage collection.

Built-ins & Environment

• Custom dynamic Hash Map built from scratch for environment variables.
• export command with OS environment synchronization (setenv).
• cd command supporting ~ (home) and - (previous directory).
• Basic utilities: help, clear, and exit.
• Variable expansion ($VAR) supporting suffix concatenation.

Interactive CLI (via Linenoise)

• Command history saving and loading (history.txt).
• Tab-completion for basic built-in commands.
• Contextual syntax hints for specific commands.

🚧 Roadmap (Pending)

• Extend ~ (tilde) expansion globally (e.g., ls ~/Documents).
• Implement Inter-Process Communication (Pipes |).
• Implement I/O Redirection (>, <, >>).
• Add Signal Handling (intercept SIGINT/SIGTSTP to protect the shell).
• Implement Background Jobs & Job Control (&, jobs, fg, bg).