[ Thanks to Andrew
Weber for this link. ]
“Stream Filtering Utilities Stream filtering allows you
to take a text file, extract only the specific data that you want
to see, and then to display it in the manner that you want to see
it. You’ll get to see several text-stream filtering utilities to
help you do this. In order to show you the full power of these
utilities, here is a quick review on the concepts of pipes and
redirectors.“When you work with text-stream filtering utilities, it only
makes sense that you would need a way to feed them some sort of
input. It also makes sense that you would need a way to see the
output, and to see error messages if something goes wrong. For
these purposes, we have stdin, stdout, and stderr.“stdin–This is short for “standard input”.”