Building a Shell (healeycodes.com)

Bit of pedantry but I don't think traditional unix shell (like this) follows repl model; the shell is not usually doing printing of the result of evaluation. Instead the printing happens more as a side effect of the commands.

Building a shell is a great exercise, but honestly having to deal with string parsing is such a bother that it robs like 2/3 of the joy along the way. I once built a very simple one in Go [0] as a learning exercise and I stopped once I started getting frustrated with all the corner cases.

[0] https://github.com/lourencovales/codecrafters/blob/master/sh...

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Had an assignment to build a shell in a week, how hard could it be?

  controlling terminal
  session leader
  job control

The parser was easy in comparison.

Some time ago I've written an article about a particular aspect of shells, job control: https://emersion.fr/blog/2019/job-control/

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Fun read. Wonder if you are able to edit text in the shell, or if you need to implement a gap buffer to allow it?

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Unix shells are conceptually simple but hide a surprising amount of complexity under the hood that we take for granted. I recently had build my own PTY controller. There were so many edge-cases to deal with. It took weeks of stress testing and writing many tests to get it right.

Interesting. I wanted to do toast | bash to let the AI drive the computer but the bash shell really got in the way. Too much complexity. The things that annoy humans, $ expansion, special characters, etc don't work for AI either. Ended up writing a custom shell for AI (and humans). When a tool gets in the way, sometimes it just time to change the tool.

Link was previously posted by author: https://news.ycombinator.com/item?id=47398749 There are other good quality articles on their site, and maybe deserves the imaginary points.

There's a very good exercise on Codecrafters (https://app.codecrafters.io/courses/shell/overview) to walk you through writing your own shell. I found it enlightening, as well as a good way to learn a new language.

Fun read! I built a minimal Linux shell [0] in c and Zig last year which does not depend on libc. It was a great way to learn about execve, the new-ish clone3 syscall and how Linux starts a process. Parsing strings is the least fun part of the building the shell.

[0] https://gist.github.com/rrampage/5046b60ca2d040bcffb49ee38e8...

Is there a (real) shell whose code is relatively short and self contained and would be valuable to read? This was always something I wanted to do but never quite spent time to look for a good one to explore.

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Great article. There are many things every developer should do when starting to learn programming or when trying to improve their skills. This is one of them. I once built a shell-like programming language (not an interpreter). If anyone reading this wants to improve their skills, I strongly suggest building your own shell from scratch.

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