DonutShell

A simple Linux shell, completely written in C.

Created by Dylan Maltos.

Goals & Objectives

• Implement a unique shell start-up sequence that immediately occurs when program is run.
• Properly handle UNIX external commands such as: ls, emacs, cd, etc.
• Properly handle internal commands such as:
  • exit: Terminate DonutShell.
  • print: Print the current PID to console.
  • help: Print the a help page to console, listing available commands for the shell.
• Support using the ampersand character (&) to seperate commands in user input, results in the given commands executing concurrently.
• Truncate a given user input line back down to 100 characters, if the input line is longer than 100 characters.
• Support arguments for commands.
• If an invalid character is found in an argument or command, print an error message, then ignore the rest of the user input line.
  • Valid characters: A-Z, a-z, 0-9, -, ., /, and _.

Build Instructions

How to correctly build and run DonutShell:

gcc -o DonutShell DonutShell.c -lm

./DonutShell

Shell Structure

• Start-up sequence:

  • A loading screen stating that DonutShell is initializing.
  • A spinning donut.
  • A screen welcomes the user to DonutShell.
  • Prompts the user for a line of input.

• Main loop:

  • Reads a given user input line and checks for:

    • Multiple commands seperated by the ampersand character (&).
    • If the input line is over 100 characters.
    • Command arguments.
    • Invalid characters in commands or arguments.

  • Executes the given user input line:

    • Commands seperated by ampersand character (&) execute concurrently.
    • Truncates user input line down to 100 characters, if over 100 characters.
    • Executes command arguments properly (ex. cd Folder/ will bring you to directory Folder/).
    • Invalid characters in given commands or arguments, result in a error message, the rest of user input line is ignored.

  • Repeats:

    • Until CTRL-C signal or internal command exit is given.