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At xargs man page there is a usage example

cut -d: -f1 < /etc/passwd | sort | xargs echo

Why in this case echo is used with xargs, and sort without,

even both command has similar syntax where arguments follows command?

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  • Have you tried it? Commented May 1, 2021 at 22:24
  • @ctrl-alt-delor Try what? It's a teorethical question about man page example. Commented May 2, 2021 at 11:27
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    Is it? both do different things. Therefore is not about the way the man page authors decided to do it. (try it: if you try it, then you will know why I asked you to try it.) Commented May 3, 2021 at 10:11

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| connects the output of the left side with the input of the right side.

echo prints its arguments. It doesn't do anything with the data sent to its input. Therefore, xargs is used to call echo with the input.

sort, on the other hand, doesn't sort its arguments, but its input data.

Therefore, it makes sense to directly put input into sort.

(However, xargs echo really makes no sense. That really only converts the output of sort to arguments, just to convert these back to output. It's not quite sure what the intention here: cut -d: -f1 < /etc/passwd | sort would have worked just the same; ok, it would have a newline after every user, but in all honesty, this isn't a job for xargs, but for sed or awk, which would have directly done what the user would've wanted in the first place, on /etc/passwd; however, I'm pretty sure you're not very interested in the sensibility of that command line, more in why xargs is used that way.)

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  • The xargs echo will end up putting the sorted values all on a single line Commented May 1, 2021 at 20:17
  • yes, I know; that's why I wrote that without, there would be a newline after every user name. Commented May 1, 2021 at 20:22
  • That difference is precisely why xargs is being used, though Commented May 1, 2021 at 21:43
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    well, yes, but it's really not a very good example of what you'd use xargs for (putting a couple thousand arguments to echo can indeed become problematic, and a single line of sed could've done the same). Anyways, I feel that's really not OP's focus, at all. Commented May 1, 2021 at 21:59
  • And xargs will do that without echo’s help — sort | xargs is sufficient here. (Or sort | tr '\n' ' '.) Commented May 1, 2021 at 21:59

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