12.7 Extended Regular Expressions

Extended regular expressions were introduced in Section 8.4, "Extended Regular Expressions" in Chapter 8 . vile provides essentially the same facilities as nvi 's extended option. The syntax is somewhat different though, relying upon additional backslash-escaped characters:

\|

Indicates alternation, house\|home .

\+

Matches one or more of the preceding regular expression.

\?

Matches zero or one of the preceding regular expression.

\(...\)

Provides grouping for * , \+ , and \? , as well as making matched sub-texts available in the replacement part of a substitute command (\1 , \2 , etc.).

\s \S

Match whitespace and non-whitespace characters, respectively.

\w \W

Match "word-constituent" characters (alphanumerics and the underscore, `_') and non-word-constituent characters, respectively. For example, \w\+ would match C/C++ identifiers and keywords.[3 ]

[3] For the pedantic among you, it also matches identifiers that start with a leading digit; usually this isn't much of a problem.

\d \D

Match digits and non-digits, respectively.

\p \P

Match printable and non-printable characters respectively. Whitespace is considered to be printable.

vile allows the escape sequences \b , \f , \r , \t , and \n to appear in the replacement part of a substitute command. They stand for backspace, formfeed, carriage return, tab and newline, respectively. Also, from the vile documentation:

Note that vile mimics perl 's handling of \u\L\1\E instead of vi 's. Given :s/\(abc\)/\u\L\1\E/ vi will replace with abc whereas vile and perl will replace with Abc . This is somewhat more useful for capitalizing words.