Simple story here really.
I had a borked config somewhere inside my /etc/ folder that was throwing some application errors. It's a development machine with poor documentation so I had to try to figure out where the typo happened.
Grep is a simple, but incredibly powerful command that took care of this quite easily. The flags I used provided the filenames that contain the matching string as well as the line number where the string is matched. Helpful for fixing or tweaking some borked config or code.
Usage is quite simple:
grep -inr "badconfigurationstring" /searchdirectory
the flags are as follows;
-i = ignore case sensitivity
-n = print line number of matching string
-r = recursively read all files under search directory
more info at the grep man page: http://linux.die.net/man/1/grep