The Open Group Base Specifications Issue 7, 2018 edition
IEEE Std 1003.1-2017 (Revision of IEEE Std 1003.1-2008)
Copyright © 2001-2018 IEEE and The Open Group


wchar.h - wide-character handling


#include <wchar.h>


[CX] [Option Start] Some of the functionality described on this reference page extends the ISO C standard. Applications shall define the appropriate feature test macro (see XSH The Compilation Environment ) to enable the visibility of these symbols in this header. [Option End]

The <wchar.h> header shall define the following types:

[CX] [Option Start] As described in <stdio.h>. [Option End]
[CX] [Option Start] As described in <locale.h>. [Option End]
An object type other than an array type that can hold the conversion state information necessary to convert between sequences of (possibly multi-byte) characters and wide characters. [CX] [Option Start]  If a codeset is being used such that an mbstate_t needs to preserve more than two levels of reserved state, the results are unspecified. [Option End]
As described in <stddef.h>.
[CX] [Option Start] As described in <stdarg.h>. [Option End]
As described in <stddef.h>.
[OB XSI] [Option Start] A scalar type of a data object that can hold values which represent locale-specific character classification. [Option End]
An integer type capable of storing any valid value of wchar_t or WEOF.

The tag tm shall be declared as naming an incomplete structure type, the contents of which are described in the <time.h> header.

The implementation shall support one or more programming environments in which the width of wint_t is no greater than the width of type long. The names of these programming environments can be obtained using the confstr() function or the getconf utility.

The <wchar.h> header shall define the following macros:

As described in <stdint.h>.
As described in <stdint.h>.
Constant expression of type wint_t that is returned by several WP functions to indicate end-of-file.
As described in <stddef.h>.

[CX] [Option Start] Inclusion of the <wchar.h> header may make visible all symbols from the headers <ctype.h>, <string.h>, <stdarg.h>, <stddef.h>, <stdio.h>, <stdlib.h>, and <time.h>. [Option End]

The following shall be declared as functions and may also be defined as macros. Function prototypes shall be provided for use with ISO C standard compilers. Arguments to functions in this list can point to arrays containing wchar_t values that do not correspond to members of the character set of the current locale. Such values shall be processed according to the specified semantics, unless otherwise stated.

wint_t        btowc(int);
wint_t        fgetwc(FILE *);
wchar_t      *fgetws(wchar_t *restrict, int, FILE *restrict);
wint_t        fputwc(wchar_t, FILE *);
int           fputws(const wchar_t *restrict, FILE *restrict);
int           fwide(FILE *, int);
int           fwprintf(FILE *restrict, const wchar_t *restrict, ...);
int           fwscanf(FILE *restrict, const wchar_t *restrict, ...);
wint_t        getwc(FILE *);
wint_t        getwchar(void);
[OB XSI][Option Start]
int           iswalnum(wint_t);
int           iswalpha(wint_t);
int           iswcntrl(wint_t);
int           iswctype(wint_t, wctype_t);
int           iswdigit(wint_t);
int           iswgraph(wint_t);
int           iswlower(wint_t);
int           iswprint(wint_t);
int           iswpunct(wint_t);
int           iswspace(wint_t);
int           iswupper(wint_t);
int           iswxdigit(wint_t);
[Option End]
size_t        mbrlen(const char *restrict, size_t, mbstate_t *restrict);
size_t        mbrtowc(wchar_t *restrict, const char *restrict, size_t,
                  mbstate_t *restrict);
int           mbsinit(const mbstate_t *);
[CX][Option Start]
size_t        mbsnrtowcs(wchar_t *restrict, const char **restrict,
                  size_t, size_t, mbstate_t *restrict);
[Option End]
size_t        mbsrtowcs(wchar_t *restrict, const char **restrict, size_t,
                  mbstate_t *restrict);
[CX][Option Start]
FILE         *open_wmemstream(wchar_t **, size_t *);
[Option End]
wint_t        putwc(wchar_t, FILE *);
wint_t        putwchar(wchar_t);
int           swprintf(wchar_t *restrict, size_t,
                  const wchar_t *restrict, ...);
int           swscanf(const wchar_t *restrict,
                  const wchar_t *restrict, ...);
[OB XSI][Option Start]
wint_t        towlower(wint_t);
wint_t        towupper(wint_t);
[Option End]
wint_t        ungetwc(wint_t, FILE *);
int           vfwprintf(FILE *restrict, const wchar_t *restrict, va_list);
int           vfwscanf(FILE *restrict, const wchar_t *restrict, va_list);
int           vswprintf(wchar_t *restrict, size_t,
                  const wchar_t *restrict, va_list);
int           vswscanf(const wchar_t *restrict, const wchar_t *restrict,
int           vwprintf(const wchar_t *restrict, va_list);
int           vwscanf(const wchar_t *restrict, va_list);
[CX][Option Start]
wchar_t      *wcpcpy(wchar_t *restrict, const wchar_t *restrict);
wchar_t      *wcpncpy(wchar_t *restrict, const wchar_t *restrict, size_t);
[Option End]
size_t        wcrtomb(char *restrict, wchar_t, mbstate_t *restrict);
[CX][Option Start]
int           wcscasecmp(const wchar_t *, const wchar_t *);
int           wcscasecmp_l(const wchar_t *, const wchar_t *, locale_t);
[Option End]
wchar_t      *wcscat(wchar_t *restrict, const wchar_t *restrict);
wchar_t      *wcschr(const wchar_t *, wchar_t);
int           wcscmp(const wchar_t *, const wchar_t *);
int           wcscoll(const wchar_t *, const wchar_t *);
[CX][Option Start]
int           wcscoll_l(const wchar_t *, const wchar_t *, locale_t);
[Option End]
wchar_t      *wcscpy(wchar_t *restrict, const wchar_t *restrict);
size_t        wcscspn(const wchar_t *, const wchar_t *);
[CX][Option Start]
wchar_t      *wcsdup(const wchar_t *);
[Option End]
size_t        wcsftime(wchar_t *restrict, size_t,
                  const wchar_t *restrict, const struct tm *restrict);
size_t        wcslen(const wchar_t *);
[CX][Option Start]
int           wcsncasecmp(const wchar_t *, const wchar_t *, size_t);
int           wcsncasecmp_l(const wchar_t *, const wchar_t *, size_t,
[Option End]
wchar_t      *wcsncat(wchar_t *restrict, const wchar_t *restrict, size_t);
int           wcsncmp(const wchar_t *, const wchar_t *, size_t);
wchar_t      *wcsncpy(wchar_t *restrict, const wchar_t *restrict, size_t);
[CX][Option Start]
size_t        wcsnlen(const wchar_t *, size_t);
size_t        wcsnrtombs(char *restrict, const wchar_t **restrict, size_t,
                  size_t, mbstate_t *restrict);
[Option End]
wchar_t      *wcspbrk(const wchar_t *, const wchar_t *);
wchar_t      *wcsrchr(const wchar_t *, wchar_t);
size_t        wcsrtombs(char *restrict, const wchar_t **restrict,
                  size_t, mbstate_t *restrict);
size_t        wcsspn(const wchar_t *, const wchar_t *);
wchar_t      *wcsstr(const wchar_t *restrict, const wchar_t *restrict);
double        wcstod(const wchar_t *restrict, wchar_t **restrict);
float         wcstof(const wchar_t *restrict, wchar_t **restrict);
wchar_t      *wcstok(wchar_t *restrict, const wchar_t *restrict,
                  wchar_t **restrict);
long          wcstol(const wchar_t *restrict, wchar_t **restrict, int);
long double   wcstold(const wchar_t *restrict, wchar_t **restrict);
long long     wcstoll(const wchar_t *restrict, wchar_t **restrict, int);
unsigned long wcstoul(const wchar_t *restrict, wchar_t **restrict, int);
unsigned long long
              wcstoull(const wchar_t *restrict, wchar_t **restrict, int);
[XSI][Option Start]
int           wcswidth(const wchar_t *, size_t);
[Option End]
size_t        wcsxfrm(wchar_t *restrict, const wchar_t *restrict, size_t);
[CX][Option Start]
size_t        wcsxfrm_l(wchar_t *restrict, const wchar_t *restrict,
                  size_t, locale_t);
[Option End]
int           wctob(wint_t);
[OB XSI][Option Start]
wctype_t      wctype(const char *);
[Option End]
[XSI][Option Start]
int           wcwidth(wchar_t);
[Option End]
wchar_t      *wmemchr(const wchar_t *, wchar_t, size_t);
int           wmemcmp(const wchar_t *, const wchar_t *, size_t);
wchar_t      *wmemcpy(wchar_t *restrict, const wchar_t *restrict, size_t);
wchar_t      *wmemmove(wchar_t *, const wchar_t *, size_t);
wchar_t      *wmemset(wchar_t *, wchar_t, size_t);
int           wprintf(const wchar_t *restrict, ...);
int           wscanf(const wchar_t *restrict, ...);

The following sections are informative.


The iswblank() function was a late addition to the ISO C standard and was introduced at the same time as the ISO C standard introduced <wctype.h>, which contains all of the isw*() functions. The Open Group Base Specifications had previously aligned with the MSE working draft and had introduced the rest of the isw*() functions into <wchar.h>. For backwards-compatibility, the original set of isw*() functions, without iswblank(), are permitted (as part of the XSI option) in <wchar.h>. For maximum portability, applications should include <wctype.h> in order to obtain declarations for the isw*() functions. This compatibility has been made obsolescent.


In the ISO C standard, the symbols referenced as XSI extensions are in <wctype.h>. Their presence here is thus an extension.




<ctype.h>, <locale.h> , <stdarg.h>, <stddef.h> , <stdint.h>, <stdio.h>, <stdlib.h>, <string.h>, <time.h>, <wctype.h>

XSH The Compilation Environment, btowc, confstr, fgetwc, fgetws, fputwc, fputws, fwide, fwprintf, fwscanf, getwc, getwchar, iswalnum, iswalpha, iswcntrl, iswctype, iswdigit, iswgraph, iswlower, iswprint, iswpunct, iswspace, iswupper, iswxdigit, mbrlen, mbrtowc, mbsinit, mbsrtowcs, open_memstream, putwc, putwchar, towlower, towupper, ungetwc, vfwprintf, vfwscanf, wcrtomb, wcscasecmp, wcscat, wcschr, wcscmp, wcscoll, wcscpy, wcscspn, wcsdup, wcsftime, wcslen, wcsncat, wcsncmp, wcsncpy, wcspbrk, wcsrchr, wcsrtombs, wcsspn, wcsstr, wcstod, wcstok, wcstol, wcstoul, wcswidth, wcsxfrm, wctob, wctype, wcwidth, wmemchr, wmemcmp, wmemcpy, wmemmove, wmemset

XCU getconf


First released in Issue 4.

Issue 5

Aligned with the ISO/IEC 9899:1990/Amendment 1:1995 (E).

Issue 6

The Open Group Corrigendum U021/10 is applied. The prototypes for wcswidth() and wcwidth() are marked as extensions.

The Open Group Corrigendum U028/5 is applied, correcting the prototype for the mbsinit() function.

The following changes are made for alignment with the ISO/IEC 9899:1999 standard:

The type wctype_t, the isw*(), to*(), and wctype() functions are marked as XSI extensions.

IEEE Std 1003.1-2001/Cor 1-2002, item XBD/TC1/D6/26 is applied, adding the APPLICATION USAGE section.

Issue 7

The mbsnrtowcs(), open_wmemstream(), wcpcpy(), wcpncpy(), wcscasecmp(), wcsdup(), wcsncasecmp(), wcsnlen(), and wcsnrtombs() functions are added from The Open Group Technical Standard, 2006, Extended API Set Part 1.

The wcscasecmp_l(), wcsncasecmp_l(), wcscoll_l(), and wcsxfrm_l() functions are added from The Open Group Technical Standard, 2006, Extended API Set Part 4.

The wctype_t type, and the isw*(), towlower(), and towupper() functions are marked obsolescent in <wchar.h> since the ISO C standard requires the declarations to be in <wctype.h>.

This reference page is clarified with respect to macros and symbolic constants, and a declaration for the locale_t type is added.

POSIX.1-2008, Technical Corrigendum 1, XBD/TC1-2008/0081 [380] is applied.

POSIX.1-2008, Technical Corrigendum 2, XBD/TC2-2008/0088 [73] is applied.

End of informative text.


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