Simple Shell in C

Overview

This C-written custom shell application offers a simple command-line interface along with a number of sophisticated capabilities. It guarantees that all instructions are executed as child processes of the shell and enables users to handle signal interruptions, control background processes, and execute normal shell commands.

Features

• Shell supports all standard shell commands like exit, pwd, clear, cd, echo, top, ps, grep, wc, cat, etc.
• Commands can be executed in the background by appending an & at the end of the command. Shell supports simultaneous execution of background commands.
• Piping is implemented (<cmd1> | <cmd2>) via pipe and dup2 syscalls. Multiple piping is allowed.
• I/O Redirection is also supported. You can overwrite a file, append to a file, or give input to a shell command from a file.
• Shell handles the CTRL+C shortcut to kill long-running commands (the shell is not exited).
• Program invocation is done by forking and child processes.

Source Code Structure

• my_shell.c: Main source file containing the shell implementation.
• utils/commands.h: Header file for command execution functions.
• utils/signalHandler.h: Header file for handling interrupts.
• utils/tokenizer.h: Header file for tokenization of the given command.
• utils/vars.h: Header file containing the global variables.

Compilation and Usage

Recommended operating system for running this program is Ubuntu.

1. To compile and run the program, execute the following in the directory that contains the my_shell.c file:

make  

./shell

2. Executing commands in foreground:

> ls -al

3. Executing command in the background:

> sleep 50 &

4. Execute some commands with pipe:

> cat my_shell.c | grep "main" | wc -l

5. Perform I/O Redirection:

   • Overwrite a file with ">"

     echo "Hello World" > test.txt
     

   • Append to a file with ">>"

     echo "Hello" >> test.txt
     

   • Input redirection with "<"

     cat < test.txt
     

6. Terminate a long-running process running in the foreground with Ctrl + C

7. Exit the custom shell and kill all background processes:

> exit

8. Clean Object files:

make clean