regexp.h — Regular expression declarations

This header is kept for historical reasons. It was part of the Legacy Feature in Single UNIX Specification, Version 2, but has been withdrawn and is not supported as part of Single UNIX Specification, Version 3. New applications should use regcomp(), regexec(), regerror() and regfree() functions and the header, which provide full internationalized regular expression functionality compatible with IEEE Std 1003.1-2001 Regular Expressions.

Applications conforming to Single UNIX Specification, Version 3 must not include the <regexp.h> header file.