A Practical Guide to Linux® Commands, Editors, and Shell Programming

Appendix A. Regular Expressions

IN THIS APPENDIX

Characters 828

Delimiters 828

Simple Strings 828

Special Characters 828

Rules 831

Bracketing Expressions 832

The Replacement String 833

Extended Regular Expressions 834

A regular expression defines a set of one or more strings of characters. 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, vim, emacs, grep, gawk, sed, and other utilities. The regular expressions used in shell ambiguous file references are different ...