6.3. Pattern-Matching Rules

In making global replacements, UNIX editors such as vi allow you to search not just for fixed strings of characters, but also for variable patterns of words, referred to as regular expressions.

When you specify a literal string of characters, the search might turn up other occurrences that you didn't want to match. The problem with searching for words in a file is that a word can be used in different ways. Regular expressions help you conduct a search for words in context. Note that regular expressions can be used with the vi search commands / and ? as well as in the ex :g and :s commands.