Take the tour ×  I was wondering how to understand the
following:   In other words, can process substitution do
whatever pipe can do?  What can process substitution do, but
pipe cannot?  share|improve this question add comment  4 Answers
up vote 20 down vote accepted  A good way to grok the difference
between them is to do a little experimenting on the command
line. In spite of the visual similarity in use of the <
character, it does something very different than a redirect or
pipe.  Let's use the date command for testing.  $ date | cat Thu
Jul 21 12:39:18 EEST 2011  This is a pointless example but it
shows that cat acceptedthe output ofdate` on STDIN and spit it
back out. The same results can be achieved by process
substitution:  $ cat <(date) Thu Jul 21 12:40:53 EEST 2011
However what just happened behind the scenes was different.
Instead of being given a STDIN stream, cat was actually passed
the name of a file that it needed to go open and read. You can
see this step by using echo instead of cat.  $ echo