grep, egrep, fgrep - print lines matching a pattern given

FORMAT
       grep [options] PATTERN [FILE...]
       grep [options] [-e PATTERN | -f FILE] [FILE...]

DESCRIPTION
       Grep  searches the named input FILEs (or standard input if no files are named, or the file name - is given) for lines containing a match to the given PATTERN.
       By default, grep prints the matching lines.

In addition, two variant programs egrep and fgrep are available.  

• Egrep is the same as grep -E.  
• Fgrep is the same as grep -F.