21.2. Regular Expressions

Utilities that process regular expressions shall support Basic Regular Expressions and Extended Regular Expressions as specified in POSIX 1003.1-2008 (ISO/IEC 9945-2009), with the following exceptions:

Range expression (such as [a-z]) can be based on code point order instead of collating element order.

Equivalence class expression (such as [=a=]) and multi-character collating element expression (such as [.ch.]) are optional.

Handling of a multi-character collating element is optional.

This affects at least the following utilities:

It also affects the behavior of interfaces in the base libraries, including at least