Learning the vi and Vim Editors, 7th Edition

Extended Regular Expressions

The metacharacters available in vi’s search and substitution regular expressions are described back in Chapter 6 in the section Metacharacters Used in Search Patterns. Each of the clones provides some form of extended regular expressions, which are either optional or always available. Typically, these are the same (or almost the same) as those provided by egrep. Unfortunately, each clone’s extended flavor is slightly different from the others’.

To give you a feel for what extended regular expressions can do, we present them in the context of nvi. The section Extended Regular Expressions describes Vim’s extended regular expressions, and each clone’s chapter in Part III describes that editor’s extended syntax, without repeating the examples.

nvi’s extended regular expressions are the Extended Regular Expressions (EREs) as defined by the POSIX standard. To enable this feature, use set extended from either your .nexrc file or from the ex colon prompt.

Besides the standard metacharacters described in Chapter 6 and the POSIX bracket expressions mentioned in POSIX Bracket Expressions in the same chapter, the following metacharacters are available:

|

Indicates alternation. For example, a|b matches either a or b. However, this construct is not limited to single characters: house|home matches either of the strings house or home.

(...)

Used for grouping, to allow the application of additional regular expression operators. For example, house|home can be shortened (if ...