Tiny Shell

A small C program that builds shell-style command arguments from user input. Written on macOS using Clang and LLDB.

This project implements command parsing, process lifecycles, signal handling, parent-level built-ins, file stream redirection, and multi-process pipelines.

Features & Implementation Details

• Reads input using fgets() with pointer protection against blank lines/empty returns
• Cleans trailing newlines dynamically via string span offsets
• Tokenizes raw buffer layouts into an optimized, NULL-terminated pointer array (my_argv[])
• Fork-replicates running processes (fork()) and overwrites child execution space with execvp()
• Pauses parent contexts securely via kernel-level wait(NULL) to maintain interface synchronization
• Supports native path manipulation built-ins (cd, exit) with full $HOME environment fallback protection
• Intercepts physical keyboard interrupts (Ctrl-C) using modern, restart-safe sigaction structures
• Swaps hardware plumbing streams (File Descriptors 0 and 1) to support robust I/O file redirection (< and >) using open() and bitwise-configured kernel permissions
• Implements concurrent multi-stage pipelines (|) by splitting memory layouts using pointer arithmetic and binding child processes together via synchronized kernel data tunnels (pipe())

Examples

Input: ls -la > files.txt
Output: Creates or overwrites files.txt with a long-form directory listing instead of outputting to the screen.

Input: ls -l | grep test
Output: Spawns two concurrent children, tunnels the directory list straight into the pattern matcher, and displays only the filtered results.

Usage

To compile and run the project locally on macOS:

# Compile with Clang
clang -Wall -Wextra -g sh.c -o sh

# Run the program
./sh

Completed Requirements

• Process execution with fork() and execvp()
• Built-in commands (cd, exit)
• Pipelines using pipe()
• I/O redirection using dup2()
• Signal handling (SIGINT)