A localedef extensions description file or extensions file defines various extensions for the localedef(1) command.
The localedef extensions description file provides:
EUC code set width information via the cswidth keyword: cswidth bc1 : sw1,bc2 : sw2,bc3 : sw3 where bc1, bc2, and bc3 indicate the number of bytes (byte count) per character for EUC codesets 1, 2, and 3, respectively. sw1, sw2, and sw3 indicate screen width for EUC codesets 1, 2, and 3, respectively.
Other extensions which will be documented in a future release.