copy multiple directories in multiple directories without loop

Question

I want to copy directories from one variable to directories from another one but without loop.

from="fromdir1 fromdir2"
to="todir1 todir2"

I mean fromdir1 to todir1, fromdir2 to todir2.

I think it can be done with xargs but I don't know how.

Hi. You've not completely stated what you want: do you want to copy each directory from from to each directory in to, or do you just want to copy the first entry of from to the first entry of to, the second entry of from to the second entry of to and so on? — Marcus Müller, Jun 21 '23 at 08:14
Hello. Thanks for the correction. I edited the post. I meant fromdir1 to todir1 and fromdir2 to todir2 — trilisser, Jun 21 '23 at 08:20
But then xargs is the wrong tool and you already have gotten a solution in a previous question of yours. You need a loop, and it goes like this: — Marcus Müller, Jun 21 '23 at 08:26
yes, I know, but that can't work. xargs doesn't do what you say you think it does, so the answer you've already gotten is the best you can get. — Marcus Müller, Jun 21 '23 at 09:04
yeah, I got it, but it was just an assumption, so the parallel solution below is appropriate — trilisser, Jun 22 '23 at 07:43

FelixJN · Accepted Answer · 2023-06-21T09:18:35.997

You could use GNU parallel with linked arguments:

parallel --link cp {1} {2} ::: from1 from2 from3 ::: to1 to2 to3

If the from and to-files are in respectives text lists, use

parallel --link cp {1} {2} :::: fromlist :::: tolist

note the 4 colons vs. 3 colons previously. More info on GNU parallel on the website.

For reading them from bash array variables, this will do:

parallel --link cp {1} {2} ::: "${from[@]}" ::: "${to[@]}"

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