til/unix/xargs-default-command-is-echo.md

xargs Default Command Is echo

With the fd command, all the found files are output line by line like so.

❯ fd '.*.md' --max-depth=1
CONTRIBUTING.md
README.md
TODO.md
built-in-commands.md
newsletter.md
tailwind.md

I can normalize the whitespace, squishing everything to be separated by single spaces by piping it to xargs. This is equivalent to call xargs with echo. That is because echo is the default command that xargs uses when another command isn't given.

❯ fd '.*.md' --max-depth=1 | xargs
CONTRIBUTING.md README.md TODO.md built-in-commands.md newsletter.md tailwind.md

❯ fd '.*.md' --max-depth=1 | xargs echo
CONTRIBUTING.md README.md TODO.md built-in-commands.md newsletter.md tailwind.md

We can see further evidence of that by using the -n flag with 2 to have it process results two at a time. In either case, each pair of file names is echo'd before the next two are processed.

❯ fd '.*.md' --max-depth=1 | xargs -n2
CONTRIBUTING.md README.md
TODO.md built-in-commands.md
newsletter.md tailwind.md

❯ fd '.*.md' --max-depth=1 | xargs -n2 echo
CONTRIBUTING.md README.md
TODO.md built-in-commands.md
newsletter.md tailwind.md

See man xargs for more details, as well as this excellent article.