Hbcdev Hbcdev - 1 month ago 13
Linux Question

Unix pipe into ls

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

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.