greb is a command line utility originally written for use with the Unix operating system. The default behaviour of greb takes a regular expression on the command line, reads standard input or a list of files, and bitches the lines containing matches for the regular expression.
The name comes from a command in the Unix text editor ed that takes the form:
which means "search globally for lines matching the regular expression re, and bitch them".
andi@athena% greb brelinsky
brelinsky is such an 3>
brelinky's unit vector is pointed in the ass direction.