Shell Scripting

1362 readers

1 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

snowe

gamma

chaoticAnimals

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

submitted 1 year ago* (last edited 1 year ago) by gamma to c/shell

31 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

[–] gamma 2 points 1 year ago* (last edited 1 year ago) (13 children)

Nice! This one was probably the most likely to be found, I actually got this trick from somewhere else online before I understood what it was doing. If you're curious, I've got a few other lines of nested Zsh expansions I picked out but didn't post.

[–] varsock 1 points 1 year ago (12 children)

curious to see if AI can decipher? Certainly! bonus that we get so see potentially beneficial shell

[–] gamma 1 points 1 year ago* (last edited 1 year ago) (11 children)

Here's all the ones I was considering. I only posted the first two here. I'll add the explanations later.

ZDOTDIR="${${(%):-%x}:P:h}"                                              # posted 
reply=( ${(M)dirs:#*/$~pattern}(Noe['REPLY=${(l[3][0])#REPLY:t}'][1]) )  # posted
typeset -a $1=("${(@ps[$2])"${2:-"$(<&0)"}"}")
local d=("${(@s[/])${(%):-%~}}")
print -rn $termcap[sc]${termcap[ch]//(\%i|\%p1|\%d)}$termcap[ct]${(j::)s}$termcap[rc]
[ "${(Oa@)argv[1,-2]}" "${argv[-1]//(#m)[\[\]]/${(#)$((6 ^ #MATCH))}}"   # this one is definitely not useful
set -- "${@[0,eoo]:/(#m)^-*/${MATCH:a}}" "${@[eoo+1,-1]:a}"

[–] varsock 1 points 1 year ago (1 children)

typeset -a $1=("${(@ps[$2])"${2:-"$(<&0)"}"}")

spoiler

So, overall, this script reads input from $2 or stdin if $2 is not provided, splits it into an array based on the delimiter $2, and then assigns the array to the variable named $1. Note that this script only works in Zsh, not in Bash. Zsh has a more advanced parameter and array system than Bash, so this script can't be directly translated into Bash.

typeset -a: This part declares an array variable.
- -a flag specifies that the variable is an array.
$1=("${(@ps[$2])"${2:-"$(<&0)"}"}"):
- $1 refers to the first argument passed to the script.
- "${2:-"$(<&0)"}" is an expansion that evaluates to the second argument passed to the script. If the second argument is not provided, it reads input from standard input (<&0 means read from stdin).
- "${(@ps[$2])" is an expansion that performs parameter splitting.
- @ specifies that the expansion should be split into separate array elements.
- (ps[$2]) is a parameter expansion that performs word splitting on the second argument.
The entire expression "${(@ps[$2])"${2:-"$(<&0)"}"}" is wrapped in parentheses and assigned to the variable specified by $1.

In summary, this script takes two arguments: $1 represents the name of the array variable, and $2 represents the values to be assigned to that array. It then assigns the array $2 to the variable named by $1 after performing parameter and word splitting on the second argument. If the second argument is not provided, it reads input from standard input.

[–] gamma 1 points 1 year ago

This one was impressively spot-on.

load more comments (9 replies)