- 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...
- The pipe section is the part that changes how you think about processes. Once you've manually done the dup2 dance — close write-end in parent, close read-end in child, wire them up — it stops being magic and starts being obvious why `grep | sort | uniq` works at all. The thing that surprised me building a similar toy was how late in the process job control has to come: you can get a working pipe chain surprisingly fast, and then job control (SIGTSTP, tcsetpgrp, the whole mess) costs 5x more than everything else combined.
- Some time ago I've written an article about a particular aspect of shells, job control: https://emersion.fr/blog/2019/job-control/
- 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...
- 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.
by ratzkewatzke
0 subcomment
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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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by leontloveless
0 subcomment
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