FWIW, while tar isn't even a POSIX command, -C is supported by bsdtar[1] (including macOS), AIX tar (confirmed AIX 7.1), and Solaris tar (confirmed Solaris 11.4

FWIW, while tar isn't even a POSIX command, -C is supported by bsdtar[1] (including macOS), AIX tar (confirmed AIX 7.1), and Solaris tar (confirmed Solaris 11.4). Argument ordering and bundling is really funky on AIX and Solaris, though, especially for extraction. [1] Seems like everybody except OpenBSD has migrated to libarchive's bsdtar, but OpenBSD also supports -C.