Magnolia Shell (mash)

A lightweight, feature-rich Unix shell written in C++17. Designed to be clean, responsive, and independent of heavy terminal dependency libraries (like readline), using direct POSIX system APIs and terminal raw mode configuration.

Features

1. Interactive Line Editing & Autocomplete

• Tab Completion: Auto-complete command names (built-ins & executables in $PATH) and file/folder paths. Directory completions automatically append a trailing slash /. Supports double-tab listing of matches.
• Command History: Navigate through previous commands using the Up and Down arrow keys. Unsaved current drafts are preserved when navigating.
• Cursor Control: Move the cursor back and forth using Left and Right arrows, or jump to boundaries using Home and End.
• Editing Tools: Modify inputs in place using Backspace and Delete keys.
• Ctrl+C / Ctrl+D Support: Pressing Ctrl+C cancels the current input line without terminating the shell. Pressing Ctrl+D on an empty line cleanly exits the shell.

2. Multi-Stage Pipelines & Redirections

• Pipelines (|): Pipe the output of one command to another (e.g., uptime | grep uptime).
• File Redirection: Redirect standard input using < and standard output using > (overwrite) or >> (append). (e.g., echo "output" > log.txt).
• Wildcard Globbing (*): Expands file glob patterns automatically (e.g., ls header/*.h or rm *.o).

3. Robust Signal & Terminal Control

• Raw terminal mode is disabled automatically before child processes execute, so full-screen applications (like nano, vim, or interactive commands like sudo) function perfectly.
• Parent process ignores SIGINT (Ctrl+C) while waiting for children, allowing child termination without exiting the shell.
• Terminal configurations are safely restored to cooked mode upon exits or abnormal terminations.

4. Smart Path & Command Parsing

• Quote Awareness: Handles arguments wrapped in single quotes '...' or double quotes "..." (e.g. mkdir "my directory").
• Escape Sequences: Supports backslash escapes \ for paths with special characters.
• Tilde Expansion: Automatically expands ~ to the user's home directory.
• Environment Variables: Automatically expands $VAR expressions (like $USER or $HOME) in commands or double quotes.

5. Rich Set of Core Built-in Commands

In addition to running external programs via execvp, mash implements the following built-ins directly:

• Navigation & Info: cd, pwd, ls (colorized table-format output), which, uptime, free.
• File & Directory Ops: mkdir, rm, touch, cp, mv, cat, head, tail, find (recursive name search).
• Ownership & Permissions: chmod, chown, chgrp.
• System Utilities: echo, date, uname, whoami, version, help, history, clear.
• Environment & Aliases: env, export, alias, unalias, source (executes shell script files).

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Build Requirements

• A compiler with support for C++17 (e.g., g++ 8+ or clang++).
• A POSIX-compliant environment (Linux or macOS).

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Getting Started

Download Pre-built Binary

You can download the compiled binaries directly from the Releases page of this repository:

• Linux (amd64): mash-linux-amd64
• macOS (Universal - Intel & Apple Silicon): mash-macos

After downloading, grant execution permissions and run:

chmod +x mash-linux-amd64 # or mash-macos
./mash-linux-amd64

Compile from Source

Compile the shell executable using the provided build script:

./build.sh

Run

Launch the shell:

./mash

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License

This project is licensed under the MIT License. See the LICENSE file for details.