Grep

Find pattern in data stream (files, standard input)

grep <pattern> <files>

Find lines matching pattern in any of the files.

When multiple files are scanned the filename is reported too (see -h below)

zgrep <pattern> <files>

Search possibly gzipped files.

Useful options

-i

Ignore case

-v

Negate the match, show all lines not having the pattern

-l

Only report filename of files with matches

-H -h

Force or suppress reporting of filenames.

-n

Report linenumber of matches too

-f <file>

Get patterns from <file>. One(1) pattern per line.

Return value ( $? )

0 (true) if one or more matches are found

1 (false) if no matches are found