Why "which cp | ls -l " is not treate as "ls -l $(which cp)"?

Question

According to pipe methodology in Linux, the output of the first command should be treated as input for the second command. So when I am doing which cp | ls -l, it should be treated as ls -l $(which cp)

But the output is showing something else.

Why so ?

Answer 1

ls does not take input from stdin. You can work around this if you need to by using xargs:

which cp | xargs ls -l

This will invoke ls -l with the (possibly multiple, if which were to return more than one) filenames as command line arguments, with no standard input.