Using Filters with Pipes - grep
To search a file for a specified string:
host% ls -l | grep Aug
-rw-r--r-- 1 pam 129 Aug 20 1986 complex.f
-rw-r--r-- 1 pam 4291 Aug 16 14:18 outdis
-rw-r--r-- 1 pam 880 Sep 28 1988 Aug.notes
To search a file for all but specified string:
host% ls -l | grep -v Aug
drwxr-xr-x 2 pam 512 Oct 23 1985 bin
-rw------- 1 pam 129 Jul 21 1987 mbox
drwxr-xr-x 2 pam 512 Jan 22 11:07 remodel
-rwxr-xr-x 1 pam 102 Jun 19 2:55 test.out