LAB 2 - GRP - 13

Introduction

Welcome to myshell, a simple command-line interpreter that mimics basic Unix shell functionality. This README serves as a guide for users to understand how to operate myshell effectively.

Features

myshell supports the following internal commands:

1. cd <directory>: Change the current default directory to <directory>. If <directory> is not provided, it reports the current directory. An appropriate error is reported if <directory> does not exist. This command also updates the PWD environment variable.
2. clr: Clear the screen.
3. dir <directory>: List the contents of directory <directory>.
4. environ: List all the environment strings.
5. echo <comment>: Display <comment> on the display followed by a new line. Multiple spaces/tabs may be reduced to a single space.
6. help: Display the user manual using the more filter.
7. pause: Pause operation of the shell until 'Enter' is pressed.
8. quit: Quit the shell.

myshell supports external command as well using the fork and exec method by following these step :

• If the command is recognized as an internal command, it is executed directly.

• If it's not an internal command, the shell forks a child process.

• In the child process, we set the parent environment variable using the setenv function.

• The external command is then executed using execvp.

• The parent process waits for the child process to finish using wait(NULL)

  Try these to test out:

1. pwd: prints the current working directory.
2. ls: is a basic command that lists the contents of the current directory.
3. echo: is used to print a message.
4. date: prints the current date and time.

myshell able to take its command line input from a file.

Try these to test out:

• create a simple batch file named batchfile with a few commands. You can modify it or add more commands as needed. Open a text editor and create a file named batchfile. Add the following commands to the file:

  1. echo This is a batch file
  2. ls
  3. pwd

• Save the file. Now, you can run your shell in batch mode using the following command:

  ./myshell batchfile

Installation & Usage

To install myshell, follow these steps:

1. Clone the repository to your local machine.

   git clone OS-LAB-2

2. Navigate to the directory containing the source code.

   cd myshell

3. Compile the source code using the provided Makefile.

   make

4. Run the compiled executable file.

   ./myshell
   

I/O Redirection

myshell supports I/O redirection using the following symbols:

• <: Redirects input from a file.
• >: Redirects output to a file.
• >>: Appends output to a file.

Exiting myshell

To exit myshell, simply type the quit command or press Ctrl + C.

Contributers

• Jumaana Aslam - 100778027
• Hasan Khan - 100820450
• Somya Babar - 100851536