“The Gates of Shell”, by Spencer Cheng, featuring Julien Barbier It’s time for the famous Simple Shell project. This is one of the most anticipated project and also one that will challenge you a lot about everything you have learn so far:
Basics of C Basics of thinking like an engineer Group work and Learning how to learn #Learning Objectives At the end of this project, you are expected to be able to explain to anyone, without the help of Google: Who designed and implemented the original Unix operating system Who wrote the first version of the UNIX shell Who invented the B programming language (the direct predecessor to the C programming language) Who is Ken Thompson How does a shell work What is a pid and a ppid How to manipulate the environment of the current process What is the difference between a function and a system call How to create processes What are the three prototypes of main How does the shell use the PATH to find the programs How to execute another program with the execve system call How to suspend the execution of a process until one of its children terminates What is EOF / “end-of-file”? 0. Betty would be proud
- Write a beautiful code that passes the Betty checks
- Simple shell 0.1
- Write a UNIX command line interpreter.
Usage: simple_shell Your Shell should:
Display a prompt and wait for the user to type a command. A command line always ends with a new line. The prompt is displayed again each time a command has been executed. The command lines are simple, no semicolons, no pipes, no redirections or any other advanced features. The command lines are made only of one word. No arguments will be passed to programs. If an executable cannot be found, print an error message and display the prompt again. Handle errors. You have to handle the “end of file” condition (Ctrl+D) You don’t have to:
use the PATH implement built-ins handle special characters : ", ', `, , *, &, # be able to move the cursor handle commands with arguments execve will be the core part of your Shell, don’t forget to pass the environ to it… 2. Simple shell 0.2
- Handle command lines with arguments
- Simple shell 0.3
- Handle the PATH fork must not be called if the command doesn’t exist
- Simple shell 0.4 *Implement the exit built-in, that exits the shell Usage: exit You don’t have to handle any argument to the built-in exit
- Simple shell 1.0
- Implement the env built-in, that prints the current environment