IMCSH

Introduction

IMCSH is a lightweight shell designed for Unix-based systems. It provides essential command-line functionality, including process management, input/output redirection, background execution, and user environment interactions.

This document serves as the official documentation, outlining the usage and implementation details of IMCSH.

Installation and Compilation

Prerequisites

IMCSH requires a Unix-like operating system (Linux, macOS), Windows is not and will not be supported.

Compilation

C compiler (e.g., GCC, Clang) is needed for development. IMCSH includes a Makefile for easy compilation. Run the following command to compile:

make

To clean up compiled files:

make clean

For immediate debugging:

make debug

Usage

Running IMCSH

To start the shell, simply execute the imcsh bin, found in the build dir.

Built-in Commands

IMCSH supports several built-in commands:

• help: Displays available commands.
• globalusage: Shows the version and authors.
• exec <program> <args>: Executes an external command.
• jobs: Lists background processes.
• exit/quit: Exits the shell, optionally terminating background processes.
• cd <directory>: Changes the current working directory.

Input/Output Redirection

IMCSH supports redirection for output:

• command > file: Redirects standard output to file (overwrites if exists).
• command >> file: Appends standard output to file.

Background Execution

Appending & to a command runs it in the background:

sleep 10 &

Use jobs to list background processes.

Implementation Details

IMCSH is implemented in C, focusing on simplicity and modularity. The core components include:

Process Management

• Uses fork() to create child processes.
• Uses execvp() to execute external commands.
• Manages background processes with waitpid().

Input Handling

• Tokenizes input using strtok().
• Detects and handles special tokens such as &, >, and >>.

Redirection Handling

• Uses open() with appropriate flags to handle file output.
• Uses dup2() to redirect output streams.

Built-in Commands

• Implemented directly in the main shell loop.
• Custom handlers for cd, exit, and jobs.

Future Enhancements

• Environment variable handling (e.g., export, unset, variable expansion).
• Additional redirection features (e.g., 2> for stderr, < for input redirection).
• Command history and alias support.
• Arrow navigation through command history
• Ctrl+C, Ctrl+D, and other control combinations
• Improved job control (e.g., suspend/resume, foreground/background management).
• Tab completion and syntax highlighting.
• Ability to execute script files.