grep is a command-line utility that allows searching of words and/or patterns in a file or group of files. Its name comes from the ed command g/re/p (globally search a regular expression and print). Grep does a global search by keyword or regular expression and print all matching lines on the standard output.
$ grep [OPTIONS] PATTERN [FILE...] $ grep [OPTIONS] [-e PATTERN | -f FILE] [FILE...]
In the second form you can specify more than one pattern using several times the -e switch or reading the pattern from a file (-f)
Basic options:
GNU extensions:
Full reading at LibreByte