A Practical Guide to Red Hat Linux: Fedora Core and Red Hat Enterprise Linux, Second Edition

Appendix A. Regular Expressions

IN THIS APPENDIX
Characters
Delimiters
Simple Strings
Special Characters
Rules
Bracketing Expressions
The Replacement String
Extended Regular Expressions

A regular expression defines a set of one or more strings of characters. Several of the Linux utilities, including vi, emacs, grep, gawk, and sed, use regular expressions to search for and replace strings. A simple string of characters is a regular expression that defines one string of characters: itself. A more complex regular expression uses letters, numbers, and special characters to define many different strings of characters. A regular expression is said to match any string it defines.

This appendix describes the regular expressions used by ed, vi, emacs, ...