UNIX® Shells by Example, Third Edition

2.1. Regular Expressions

2.1.1. Definition and Example

For users already familiar with the concept of regular expression metacharacters, this section may be bypassed. However, this preliminary material is crucial to understanding the variety of ways in which grep, sed, and awk are used to display and manipulate data.

What is a regular expression? A regular expression^[1] is just a pattern of characters used to match the same characters in a search. In most programs, a regular expression is enclosed in forward slashes; for example, /love/ is a regular expression delimited by forward slashes, and the pattern love will be matched any time the same pattern is found in the line being searched. What makes regular expressions interesting is that they ...