Coding Challenge #14 - Build Your Own Shell

This challenge is to build your own shell.

A shell is a program that exposes the operating system’s services to us, the user of the system. We’re going to focus on the command line versions, like sh, bash, zsh and others.

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Ok let’s get into the challenge of building a shell….

The Challenge - Building Your Own Shell

I use zsh on my MacBook, here’s what the man page says about it:

Zsh is a UNIX command interpreter (shell) usable as an 
interactive login shell and as a shell script command 
processor.        

We’re going to build our shell, which will enable us to run commands on our operating system.

Step Zero

Please set up your IDE / editor and programming language of choice and proceed directly to step 1 once you’re ready. I’ve called my project ccsh for Coding Challenges Shell.

Step 1

In this step your goal is to create the simples possible command line shell. That’s a program that starts up waits for the user to type in a command. To make it easier to see which shell is running I’ve given my shell a unique prompt: ccsh>.

When the user enters a command we’ll need to trim any trailing whitespace or newline characters and then spawn a new process to run the entered command.

For example here’s what happens when I run my ccsh:

% ccsh
ccsh> ls
Cargo.lock      Cargo.toml      src             target
%         

My shell outputs the prompt ccsh>. I have then run the command ls and it has output the results below the prompt. In this case you see the files from my Rust implementation of ccsh.

Note that ccsh immediately terminates after running the command, returning me to the normal shell.

Continued...

You can find Step 2 and beyond on the?Coding Challenges?website as?Write You Own Shell.

Or if you'd rather get the whole challenge delivered to you inbox every week, you can subscribe on the?Coding Challenges Substack.