Manual Pages  — MULTIBYTE

The current locale (setlocale(3)) governs the interpretation of wide and multibyte characters. The locale category LC_CTYPE specifically controls this interpretation. The wchar_t type is wide enough to hold the largest value in the wide character representations for all locales.

Multibyte strings may contain 'shift' indicators to switch to and from particular modes within the given representation. If explicit bytes are used to signal shifting, these are not recognized as separate characters but are lumped with a neighboring character. There is always a distinguished 'initial' shift state. Some functions (e.g., mblen(3), mbtowc(3) and wctomb(3)) maintain static shift state internally, whereas others store it in an mbstate_t object passed by the caller. Shift states are undefined after a call to setlocale(3) with the LC_CTYPE or LC_ALL categories.

For convenience in processing, the wide character with value 0 (the null wide character) is recognized as the wide character string terminator, and the character with value 0 (the null byte) is recognized as the multibyte character string terminator. Null bytes are not permitted within multibyte characters.

The C library provides the following functions for dealing with multibyte characters:

Function	Description
mblen(3)	get number of bytes in a character
mbrlen(3)	get number of bytes in a character (restartable)
mbrtowc(3)	convert a character to a wide-character code (restartable)
mbsrtowcs(3)	convert a character string to a wide-character string (restartable)
mbstowcs(3)	convert a character string to a wide-character string
mbtowc(3)	convert a character to a wide-character code
wcrtomb(3)	convert a wide-character code to a character (restartable)
wcstombs(3)	convert a wide-character string to a character string
wcsrtombs(3)	convert a wide-character string to a character string (restartable)
wctomb(3)	convert a wide-character code to a character