Simple Shell Program in C

This is a simple shell program implemented in C. The program reads user input, tokenizes the command, and uses fork() and execvp() system calls to execute the command. The current time is displayed before each command prompt.

Features

• Displays the current time before each command prompt.
• Supports basic shell commands like ls, pwd, etc.
• Exits when the user types exit.
• Handles child process creation and execution using fork() and execvp().
• Error handling for unknown commands and unsuccessful child process creation.

Prerequisites

Ensure that GCC (GNU Compiler Collection) is installed on your system.

Installing GCC

On Linux:

Ubuntu or Debian-based systems:

sudo apt update
sudo apt install gcc

Fedora, RHEL, or CentOS:

sudo dnf install gcc

Arch Linux:

sudo pacman -S gcc

To verify the installation:

gcc --version

On Windows:

To install GCC on Windows, you can use MinGW (Minimalist GNU for Windows) or Cygwin.

MinGW Installation Steps:

1. Download the MinGW installer from the MinGW website.
2. Run the installer and select the gcc package.
3. Follow the prompts to complete the installation.
4. Add the path to MinGW (C:\MinGW\bin) to your system’s PATH environment variable:
   • Right-click on This PC or Computer > Properties > Advanced system settings > Environment Variables.
   • Find the Path variable in System variables, click Edit, and add C:\MinGW\bin.

To verify the installation:

gcc --version

Cygwin Installation:

1. Download and run the Cygwin installer from Cygwin’s official site.
2. During installation, select the gcc-core package.
3. Follow the steps to complete the installation.
4. Add the Cygwin bin directory (e.g., C:\cygwin64\bin) to your PATH environment variable.

Building the Program

Clone the repository and navigate to the directory containing the source file. Use GCC to compile the program:

gcc -o simple_shell simple_shell.c

This will create an executable file named simple_shell.

Running the Program

On Linux or macOS:

Run the compiled program using:

./simple_shell

On Windows:

Run the compiled program using:

simple_shell.exe

If you encounter issues with fork() or execvp() on Windows, consider running the program in a Linux environment using Windows Subsystem for Linux (WSL) or using a virtual machine with Linux installed.

Usage

• The program displays the current time before each command prompt.
• Type any valid shell command and press Enter to execute it.
• To exit the shell, type exit and press Enter.

References

• GeeksforGeeks - Array of Strings in C
• Stack Overflow - Split String into Tokens
• Tutorials Point - Local Time Function
• Execvp Documentation

For more details, check out the comments and links within the code.

License

This project is licensed under the MIT License.