Abyss Shell

A custom, fully functional Unix shell built from scratch in bare-metal C.

This project was developed to gain a deep, unabstracted understanding of operating system mechanics, process management, and kernel-level inter-process communication (IPC). It directly interacts with Linux system calls to manage memory, execute programs, and route data streams.

Features

• Process Creation & Control: Utilizes fork(), execvp(), and wait() to spawn and manage child processes safely within the parent shell environment.
• Pipeline Support: Handles complex multi-stage pipelines (e.g., ls -la | grep .c | wc -l) with dynamic pipe allocation, efficient file descriptor routing, and proper cleanup to prevent deadlocks.
• Two-Phase Parsing: Implements a strict parsing algorithm to handle both pipe operators and command arguments without strtok state corruption.
• Built-in Commands: Supports cd and exit commands executed directly in the parent process.
• Error Handling: Comprehensive error checking and reporting for system calls.

Technical Details

Component	Details
Language	C (C99 standard)
Build System	GNU Make
Environment	Linux (kernel 4.4+)
Key APIs	fork(), execvp(), pipe(), dup2(), wait(), chdir()
Compiler	GCC with strict warnings enabled

Installation & Build

Ensure you have gcc and make installed:

# Clone the repository
git clone https://github.com/yansh07/abyss-shell.git
cd abyss-shell

# Build the shell
make

# Run the shell
make run

Usage

Once built, run the shell:

./bin/abyss-shell

Then use standard Unix commands:

abyss-shell> ls -l | grep .c
abyss-shell> cat file.txt | sort | uniq
abyss-shell> pwd
abyss-shell> cd /path/to/dir
abyss-shell> exit

Build Targets

• make — Compile the executable
• make run — Build and run the shell
• make clean — Remove build artifacts
• make help — Show available targets

License

MIT License — See LICENSE file for details.