I created a simple alias for xargs, with the intend to pipe it when needed. It will simply run a command for each line of it. My question to you is, is this useful or are there better ways of doing this? This is just a little bit of brainstorming basically. Maybe I have a knot in my head.

# Pipe each line and execute a command. The "{}" will be replaced by the line.
# Example:
#   find . -maxdepth 2 -type f -name 'M*' | foreach grep "USB" {}
alias foreach='xargs -d "\n" -I{}'

For commands that already operate on every line from stdin, this won’t be much useful. But in other cases, it might be. A more simplified usage example (and a useless one) would be:

find . -maxdepth 1 | foreach echo "File" {}

It’s important to use the {} as a placeholder for the “current line” that is processed. What do you think about the usefulness? Have you any idea how to use it?

  • davel [he/him]@lemmy.ml
    3·
    5 months ago

    A bit of a tangent, but I almost never use xargs in the shell anymore, and instead use “while read line ; do *SOMETHING* $line ; done”, because xargs doesn’t have access to the shell’s local variables, aliases, or functions.

    • thingsiplay@beehaw.orgOP
      1·
      5 months ago

      Good point! A while loop is probably more flexible here and easier to expand too. I will experiment a bit more and maybe I’ll change to a while readline implemented as a Bash function.

    • dcdc@programming.dev
      1·
      5 months ago

      True that the loop is easier to work with, though you can still pass args/env into the sub shell, and xargs’ -P is one of my favorites depending on the task (may not be desired in this case). Sometimes I’ve done both: echo assembled commands in a loop/find -exec, sanity check output, then pipe to xargs … bash -c to run in parallel.

  • kittenroar@beehaw.orgEnglish
    3·
    5 months ago

    Great minds, lol. I have almost the exact same command set up as a little script. Mine has an extra modification for my use case, and I named mine iter, but foreach is a good name for it too.

      • kittenroar@beehaw.orgEnglish
        2·
        5 months ago

        Here’s the code:

        #!/bin/bash
cmd=$@
if echo $cmd | grep '/$'
then
    xargs -rd '\n' -I {} $cmd{}
else
    xargs -rd '\n' -I {} $cmd {}
fi

        Usage is like:

        ls *zip | iter shasum

        or

        ls *zip | iter shasum ../zipfile_archive/

        The second one would get the shasum of zip files that have the same name as ones in the cwd

        This assumes, of course, that the input files have sane names, ie, no spaces, etc

        • thingsiplay@beehaw.orgOP
          2·
          5 months ago

          Thanks for posting. I find the echo part and extra use of variable is a little bit flaky. Here is a modified version. But I am not 100% sure if its doing what your script is doing.

          I skipped the extra variable and echo and grep, by comparing its content with ${*}, which is similar to ${@}, but won’t separate each argument and create a single string instead. The =~ /$ is a regex comparison, which Bash supports native. Then I am using ${@} for the call, which separates each argument. Maybe this could be done with ${*} instead. I’m not sure which of them is the correct one for this case. At least it seems filenames with spaces work. Otherwise, not claiming it would be better. Just giving some food for thoughts.

          #!/usr/bin/bash

if [[ "${*}" =~ /$ ]]; then
    xargs -rd '\n' -I {} "${@}"{}
else
    xargs -rd '\n' -I {} "${@}" {}
fi
  • F04118F@feddit.nl
    2·
    5 months ago

    How to call xargs is typically one of those things I always forget. The foreach alias is a great solution!

    My current solution was to use tldr for all of these tools, but yeah if I find myself having to do a for each line, I’ll definitely steal your alias.

    Luckily (knocks on wood) I almost exclusively work with yaml and json nowadays so I should just learn yq.