k-shell 🐚

A custom Unix shell implementation written in C. Designed to explore core Operating System concepts including process creation, memory management, and system calls.

🚀 Features

Phase 1: The Foundation (Current)

• REPL Interface: A robust Read-Eval-Print Loop handling interactive user input.
• Process Execution: Uses fork(), execvp(), and wait() to run external programs (e.g., ls, grep, git).
• Native File Management: Built-in implementation of cp, mv, rm, touch, mkdir, and rmdir using standard C I/O streams.
• System Diagnostics: Built-in tools to check system time, uptime, and network identity (date, uptime, hostname).
• Text Processing: Native string and file analysis tools (head, wc, rev).
• Environment Control: Ability to modify the shell environment dynamically using export and unset.
• Productivity Tools: Includes mkcd (atomic make-and-enter) and a built-in calc (arithmetic engine).
• Documentation System: Context-aware help system (e.g., typing help cd gives specific usage examples).
• Visuals: Colored ANSI output and custom kfetch system branding.

🛠️ Built-in Commands

Core & Navigation

Command	Description
cd <dir>	Change the current working directory.
mkcd <dir>	Create a directory and immediately enter it.
pwd	Print the current working directory.
exit	Terminate the shell session safely.
help [cmd]	Display the user guide or specific command manual.

File Management

Command	Description
touch <file>	Create a new empty file or update timestamp.
rm <file>	Delete a file permanently.
mkdir <dir>	Create a new directory.
rmdir <dir>	Remove an empty directory.
cat <file>	Display file contents to the terminal.
cp <src> <dst>	Copy a file from source to destination.
mv <src> <dst>	Move or rename a file.

System & Time

Command	Description
date	Display the current date and time.
uptime	Show how long the system has been running.
hostname	Display the network name of the computer.
sleep <sec>	Pause the shell for a specific number of seconds.
kfetch	Display system information and shell branding.

Text Tools

Command	Description
head <file> [n]	Print the first N lines of a file (default 5).
wc <file>	Count lines, words, and bytes in a file.
rev <text>	Reverse a string (e.g., hello -> olleh).
echo <text>	Print text to the standard output.

Environment & Misc

Command	Description
env	Print all environment variables.
export <k=v>	Create or update an environment variable.
unset <key>	Remove an environment variable.
whoami	Display the current username.
type <cmd>	Identify if a command is a built-in or external executable.
calc <expr>	Perform basic arithmetic (e.g., calc 10 + 5).
clear	Clear the terminal screen and scrollback.

⚙️ Installation & Usage

Prerequisites

• OS: Linux (Ubuntu/Fedora) or Windows (via WSL2).
• Compiler: GCC.
• Build Tool: Make.

Building the Shell

1. Clone the repository:

   git clone git@github.com:Kedrich/k-shell.git
   cd k-shell

2. Compile using the Makefile:

   make

3. Run the shell:

   ./k-shell

🧠 Learning Objectives

The primary goal of this project is to demystify Operating System internals by building them from scratch. Core Objectives:

• To understand System Calls: specifically how fork, exec, and wait interact with the kernel.
• To practice Low-Level String Parsing: handling raw C strings without high-level abstractions.
• To master Process Management: managing the lifecycle of child processes and signals.
• To explore Memory Management: (Upcoming in Phase 2) transitioning from stack to heap allocation.

🗺️ Roadmap

• Phase 1: Basic Execution & Built-ins (Completed)
• Phase 2: Dynamic Memory Management (Heap allocation)
• Phase 3: I/O Redirection (>, <) & Pipes (|)
• Phase 4: Command History & Configuration

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Created by Kedrich.