MyShelf - Custom Unix Shell

Advanced Systems Programming

Paris 8 University (Bachelor Legacy) 2019 Original Development

2026 Refactored for Translation.

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📌 Overview

MyShelf is a functional Unix-like shell developed in C. It was created as the final project for the Operating Systems course at Paris 8 University. It implements the core mechanics of a command-line interpreter, focusing on process lifecycle management, environment handling, and I/O stream manipulation.

Starting from a foundational academic version, this 2026 edition focuses on code translation.

🚀 Implemented Features

📂 Built-in Commands

• cd [path]: Manual implementation of directory navigation.
  - Supports relative and absolute paths with call of chdir().
  - Handles special symbols: . (current), .. (parent), and ~ (home).
  - Includes a security check to prevent navigating above the /home directory.

• exit: Gracefully terminates the shell session.

⚙️ Process Management

• Execution: Launches external binaries using fork(), execv(), and wait().

• Background Tasks (&): Supports non-blocking process execution.
  - Displays the Process ID (PID) upon launch.
  - Monitors child processes to provide termination notifications and prevent zombie processes (using waitpid logic).

• PATH Resolution: Automatically searches for executables within the directories defined in the system's PATH environment variable.

⚙️ I/O & IPC

• Redirections: Implements standard input (<) and output (>) redirection to files using dup2 and fcntl logic.

• Pipes (|): Supports sequential command chaining where the output of one process is piped as the input to the next.

✨ Bonus Feature

• File Auto-completion: Advanced implementation allowing users to complete filenames using the Tab key, integrated within the terminal read logic.

🏗 Architecture & Internal Logic

The shell follows a modular REPL (Read-Eval-Print Loop) design:

• Lexer/Parser: A custom decouper function tokenizes the input string based on delimiters (spaces, tabs, newlines)

• String Manipulation: Specific internal functions like cutstr and selectstr are used for complex parsing of command arguments.

• System Headers: Uses a dedicated sys.h to manage critical includes like unistd.h, sys/wait.h, and sys/stat.h.

• Executor: Handles the logic of forking, searching the PATH, and executing system calls.

• Process Monitor: A core routine that monitors background tasks (&) and ensures terminated child processes are properly reaped to prevent system resource exhaustion (zombie processes).

🛠 2026 Refactoring

• Memory Management: Fixed specific memory leaks (e.g., in the stat buffer and string duplications) to ensure stability.

• Language Translation: All internal code comments and user-facing messages have been translated from French to English.

📦 Installation & Usage

Bash

Clone the repository

git clone https://github.com/your-repo/myshelf.git

cd myshelf

Compile using the provided Makefile

 make

Launch MyShelf

 ./myshelf