Shell Scripting

1349 readers

4 users here now

From Ash, Bash and Csh to Xonsh, Ysh and Zsh; all shell languages are welcome here!

Rules:

Follow Lemmy rules!
Posts must relate to shell scripting. (See bottom of sidebar for more information.)
Only make helpful replies to questions. This is not the place for low effort joke answers.
No discussion about piracy or hacking.
If you find a solution to your problem by other means, please take your time to write down the steps you used to solve your problem in the original post. You can potentially help others having the same problem!
These rules will change as the community grows.

Keep posts about shell scripting! Here are some guidelines to help:

Allowed: Release Announcement of a command-line program designed for scripted use (e.g. bash, bats, awk, jq, coreutils/moreutils)
Allowed: Tutorials on using shell languages or supplementary tools designed for scripted use
Allowed: Code review/help requests for shell languages or supplementary tools designed for scripted use
NOT Allowed: Announcement of a CLI or TUI program that is not designed for scripted use (Yes, your fancy Zsh plugin which pretty-prints the date and time using only builtins is very cool, but unless you actually want to discuss the code itself, please check out !commandline instead!)
NOT Allowed: Domain-specific tutorials that do not involve shell scripting as a core component (e.g. docker-compose, ansible, nix). If you really love one of these, I'm sure there's a community out there ready to talk about them!
NOT Allowed: Code review requests for non-shell programming languages and configuration languages (e.g. Python, Yaml)

In general, if your submission text is primarily shell code, then it is welcome here!

founded 1 year ago

MODERATORS

[email protected]

What are the most inscrutable lines of $SHELL you've ever written? (programming.dev)

submitted 1 year ago* (last edited 1 year ago) by [email protected] to c/[email protected]

48 comments fedilink hide all child comments

I'm sure some of you have absolute monstrosities of sigils (I know I do, in my .zshrc alone). Post them without context, and try and guess what other users's lines are. If you want to provide context or guess, use the markdown editor to spoiler-tag your guesses and explanations!

you are viewing a single comment's thread
view the rest of the comments

[–] [email protected] 3 points 1 year ago

Two of the most expensive things a shell does are call fork and call execve for an external program. pwd is a builtin (at least for bash) but the former still applies. $PWD exists even if you don't want that shortening; just like your backticks be sure to quote it once so it doesn't get expanded when assigning to PS1.

In general, for most things you might want to do, you can arrange for variables to be set ahead of time and simply expanded at use time, rather than recalculating them every time. For example, you can hook cd/pushd/popd to get an actually-fast git prompt. Rather than var=$(some_function) you should have some_function output directly to a variable (possibly hard-coded - REPLY is semi-common; you can move the value later); printf -v is often useful. Indirection should almost always be avoided (unless you do the indirect-unset bash-specific hack or don't have any locals) due to shadowing problems (you have to hard-code variable name assumptions anyway so you might as well be explicit).