Unix pipe into ls

linux unix pipe ls
hcarver picture hcarver · Aug 13, 2013 · Viewed 20.8k times · Source

I thought I understood *nix pipes until now... I have an executable called studio which symlinks to my install of Android Studio and I had assumed I could get the linked-to location with 

which studio | ls -l

But that doesn't work. What it gives me is equivalent to having just run ls -l in the current directory.

If I run which studio, I get /home/me/bin/studio. And if I run ls -l /home/me/bin/studio I get the expected output showing me the symlink location.

So why doesn't the piped version work? What haven't I grokked about pipes?

Answer

fedorqui 'SO stop harming' picture fedorqui 'SO stop harming' · Aug 13, 2013

To do that you need xargs:

which studio | xargs ls -l

From man xargs:

xargs - build and execute command lines from standard input

To fully understand how pipes work, you can read What is a simple explanation for how pipes work in BASH?:

A Unix pipe connects the STDOUT (standard output) file descriptor of the first process to the STDIN (standard input) of the second. What happens then is that when the first process writes to its STDOUT, that output can be immediately read (from STDIN) by the second process.

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