My Shell

A simple yet powerful custom shell implementation in C. This shell supports basic command execution, environment variable handling, I/O redirection, and pipeline functionality.

Features

• Command Execution: Execute standard shell commands.
• Environment Variables: Handle environment variables (e.g., VAR=value).
• I/O Redirection: Supports input (<), output (>), and append (>>) redirection.
• Pipelines: Execute multiple commands in a pipeline (e.g., cmd1 | cmd2 | cmd3).
• Change Directory: Built-in cd command to change directories.
• Error Handling: Robust error handling for invalid commands, directories, or redirections.

Prerequisites

• GCC: To compile the C code.
• Linux/Unix Environment: The shell is designed to run on Unix-like systems.

Usage

Clone the Repository:

git clone https://github.com/your-username/my-shell.git
cd my-shell

Compile the Shell:

gcc -o my_shell main.c my_shell.c

Run the Shell:

./my_shell

Code Structure

Files

• main.c: The main entry point for the shell.

  • Handles user input, command execution, and pipeline detection.
  • Manages the shell loop and exit conditions.

• my_shell.c: Contains the core functionality of the shell.

  • handle_variable: Handles environment variable assignments.
  • read_command: Reads user input.
  • build_args: Tokenizes the input into arguments.
  • set_program_path: Sets the full path for command execution.
  • change_directory: Implements the cd command.
  • io_redirection: Handles input/output redirection.
  • pipeline: Executes commands in a pipeline.

• my_shell.h: Header file containing function declarations and constants.

Key Functions

• handle_variable: Processes environment variable assignments (e.g., VAR=value).
• read_command: Reads and processes user input.
• build_args: Splits the input command into arguments.
• set_program_path: Constructs the full path for command execution.
• change_directory: Implements the cd command.
• io_redirection: Handles input/output redirection.
• pipeline: Executes commands in a pipeline.

Example Workflow

Start the shell:

./my_shell

Run commands:

MY_VAR=world
echo $MY_VAR > output.txt
cat output.txt
ls -l | grep "output.txt"
cd /home/user

Exit the shell:

exit