Authorize: Jonathan Elgarisi

Shell Program

This is a simple shell program written in C for Linux-based machines. It reads commands from the user or a script file, executes them, and handles special commands like "alias", "unalias", and "source". It also counts the number of commands, script lines, and commands that contains quotes. It uses a stack to check for quotes in the input.

Features

• Execute commands from user input or a script file. -Handle special commands: "alias", "unalias", and "source".
• Count the number of commands, script lines, and commands that contain quotes. - Check for matching quotes in the input using a stack.
• Support for && and || operators.
• Support for & operator.
• Support for 2> operator.
• Support for jobs command.

How to Run

To compile the program, use the following command:

#!/bin/bash gcc -Wall ex1.c -o ex1

Or use the run_me.sh script file as an alternative to compiling it yourself.

How to Use

After succesfully launching the script or the command lines provided above you can enter Linux commands or using one of the special commands.

*Special Commands: -alias: creates a shortcut for a command in the format alias <name>='<command>' and will save it in a linked-list strcture. In order to see the aliases list enter the word alias.

        alias ll='ls -l' #will assaign ll as a shortcut for the command ls -l. then, typing alias will result with the output: ll='ls -l'

-unalias: to remove a shortcut from the aliases list

        unalias ll #will remove the shortcut ll from the aliases linked-list) 

-source: running script files, in order to use this command enter this format source <script_file_name.including_extention>

        source script.sh will run the script.sh file located at the same folder as this shell)

-exit_shell: closes the shell program and prints the number of commands that contained quotes.

-jobs: displays all processes running in the background. Example:

        sleep 50 & 
        sleep 50 &
        sleep 50 &
        #Starts 3 background processes.

        jobs #Shows all running background processes with their PIDs.
        [1] sleep 50 & 
        [2] sleep 50 & 
        [3] sleep 50 &

Additional Features:

• && and || operators: These operators allow conditional execution of commands.
• &&: Command2 will run only if Command1 successfully executed.
• ||: Command2 will run only if Command1 failed to execute. Example:

                asdf && ls #asdf is not a valid command, so ls will not be executed. 
                asdf || ls asdf is not a valid command, so ls will be executed.

& operator: The & character at the end of a command will run the command in the background, allowing the user to run more commands immediately. Example:

        sleep 5 #Runs sleep for 5 seconds, and the shell is "stuck" during this time.
        sleep 5 & #Runs sleep for 5 seconds in the background, allowing immediate command input.

2> operator: Redirects error output (stderr) to a file. Example:

         command 2> error_log #Runs the command, writing any error messages to the file error_log. 
         aaaa 2\> E #aaaa is not a valid command, so its error message is written to E. cat E will print the error message from the file.
         (aaa && ls) 2\> EE #If aaa is invalid, its error message is written to EE, and ls will not be executed.

Output

According to your commands. Errors will be provide information if occurs.

Files

• ex1.c: The main file containing the shell program.
• Stack.h: Contains the definition and functions for a stack data structure used for checking matching quotes.
• Alias.h: Contains the definition and functions for handling command aliases.
• Jobs.h: Contains the definition and functions for handling background jobs.
• runData.h: Contains the definition for tracking script lines and quote counts.
• run_me.sh: A script file to run the shell program.
• README.txt: The text file you're currently reading.

License

MIT- https://choosealicense.com/licenses/mit/