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Help me understand bash syntax (programming.dev)
submitted 10 months ago by to c/linux@programming.dev
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I was trying to find all symbolic links in /usr/lib and use file on the first entry in the list, which I delimited with head -n 1.

Why does find /usr/lib -maxdepth 1 -type l | file $(head -n 1) work but find /usr/lib -maxdepth 1 -type l | head -n 1 | file does not?

It complains that I am not using file correctly. Probably because it lacks an argument, but - programmatically/syntactically - why can't file grab it's argument from the pipe?

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[–] 18 points 10 months ago (4 children)

Your syntax is fine, but not all commands/programs accept input from the pipe, or more accurately from stdin. Looking at the man page for file (https://www.man7.org/linux/man-pages/man1/file.1.html) I can't see a stdin option, so you have to pass each of the files from your head output as arguments to file.

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  • [–] 6 points 10 months ago (2 children)

    I learned this the hardway with ffmpeg... In my defense... Their documentation IS huge !!!

    Kinda interested if 2>&1 would also work in this case?

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  • [–] 10 points 10 months ago (1 child)

    2>&1 pipes stderr to stdout, which would not affect a binary like file which doesn't parse stdin. You would need something like xargs file which would convert the stdout to command line arguments.

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