grep as a Filter

You can use the grep command as a filter with other commands, enabling you to filter out unnecessary information from the command output. To use grep as a filter, you must pipe the output of the command through grep. The symbol for pipe is “|”.

The following example displays files that end in “.ps” and were created in the month of September.

$ ls -l *.ps | grep Sep

The first part of this command line produces a list of files ending in .ps.

$ ls -l *.ps
-rw-r--r--   1 user2    users     833233 Jun 29 16:22 buttons.ps
-rw-r--r--   1 user2    users      39245 Sep 27 09:38 changes.ps
-rw-r--r--   1 user2    users     608368 Mar  2  2000 clock.ps
-rw-r--r--   1 user2    users     827114 Sep 13 16:49 commands.ps
$

The second part of the command line pipes that list through grep, looking for the pattern Sep.

| grep Sep

The search provides the following results.

$ ls -l *.ps | grep Sep
-rw-r--r--   1 user2    users      39245 Sep 27 09:38 changes.ps
-rw-r--r--   1 user2    users     827114 Sep 13 16:49 commands.ps
$