/regex/ Match lines matching the regular expression regex. Addr1,+N Will match addr1 and the N lines following addr1. Cregexc Match lines matching the regular expression regex. The c may be any character. Addr1,N Will match addr1 and the lines following addr1 until the next line whose input line number is a multiple of N. A regular expression, regex or regexp is a sequence of characters that define a search pattern. Usually such patterns are used by string searching algorithms for 'find' or 'find and replace' operations on strings, or for input validation.
Grep is a handy command-line utility that enables you to search text or files.
More formally: Grep (Global Regular Expression Print) is a utility for searching plain-text datasets for lines that match a given regular expression.
Grep was developed for Unix, but is now available for all unix-like systems (e.g. Linux).
Basic Command Syntax
Ignore Case
Use -i:
Recursive Search
Use -r:
To suppress the filename. use the -h option. This example shows suppressed filenames and sends the result output to a file:
Search for Whole Words
Grep will return lines that contain the target string - it may be a fragment of another string. To return only lines containing the target string as a distinct word, use the -w option:
Regular Expression Examples Linux
Search for many words requires egrep (extended grep), or escaping the pipe character:
Regex Cheat Sheet
References