Possible solutions and their relationships to POSIX and Unicode What should a library do to support developers and make developing applications easier? We will explore current and upcoming solutions in the next sections. In practice, it works as expected in many, but not all, locales. In theory, users should employ bracket expressions such as ] and ]. English with UTF-8 characters.įor most programs and users, therefore, a popular regular expression range such as or has undefined and ultimately unreliable behavior. Most people specify their country and language when setting up their system and get a locale such as en_US.UTF-8, in this case, indicating U.S.

This locale applies only to programs or environments whose environment variables for the locale (such as LANG or LC_ALL) specify either POSIX or C, or who don't have those environment variables set at all. Under the POSIX standard, a regular expression using a range expression has unspecified behavior in any locale other than the POSIX locale. The problem with regular expression ranges This article delves into the issues with using ranges in different locales and the solutions sought by developers of various libraries, including the GNU C Library (glibc). However, they often don't realize that these regular expressions harbor problems that can lead to unexpected behavior. Developers as well as casual grep users are accustomed to using ranges in regular expressions, such as or.

Grep regex one of two strings