> so he is required by the standard the implement \X. Which standard is that? If you're talking about Unicode, the "standard" for regular expressions[1] is an

> so he is required by the standard the implement \X. Which standard is that? If you're talking about Unicode, the "standard" for regular expressions[1] is an "Unicode Technical Standard", which according to itself isn't required for Unicode conformance: > A Unicode Technical Standard (UTS) is an independent specification. Conformance to the Unicode Standard does not imply conformance to any UTS. So awk can claim Unicode support without supporting "\X" (like many regex engines). If you're talking about POSIX, its regex chapter[2] doesn't mention "\X". In any case I don't think awk claims to conform to POSIX. [1] https://unicode.org/reports/tr18/ https://unicode.org/reports/tr18/ [2] https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap09.html https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1...