LAB 2 - GROUP 1 - CRN: 74026

Contributors

• Harsh Tamakuwala - ID: 100824220
• Syed Nasir Hussain Naqvi - ID: 100809447
• David Hanna - ID: 100828635

Overview

myshell is a basic command-line interpreter designed to replicate fundamental Unix shell functionalities. This README offers comprehensive guidance for users to effectively navigate and utilize myshell.

Key Features

myshell offers several internal commands:

1. cd <directory>: Changes the current default directory to <directory>. If <directory> is unspecified, the current directory is displayed. An appropriate error message is shown if <directory> does not exist. This command also updates the PWD environment variable.
2. clr: Clears the screen.
3. dir <directory>: Lists the contents of directory <directory>.
4. environ: Displays all environment strings.
5. echo <comment>: Shows <comment> on the display followed by a new line. Multiple spaces/tabs are reduced to a single space.
6. help: Exhibits the user manual using the more filter.
7. pause: Halts operation of the shell until 'Enter' is pressed.
8. quit: Exits the shell.

myshell also supports external commands through the fork and exec method:

• 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, the parent environment variable is set 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 commands to explore:

1. pwd: Displays the current working directory.
2. ls: Lists the contents of the current directory.
3. echo: Prints a message.
4. date: Shows the current date and time.

Additionally, myshell is capable of taking command line input from a file.

To test this functionality:

• Create a simple batch file named batchfile with desired commands.
• Run the shell in batch mode using: ./myshell batchfile

Installation & Usage

To install myshell, follow these steps:

1. Clone the repository to your local machine.

   git clone OS_LAB2-MyShell

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.