#include <wctype.h>
The <wctype.h> header shall define the following types:
The <wctype.h> header shall define the locale_t type as described in <locale.h>.
The <wctype.h> header shall define the following macro:
For all functions described in this header that accept an argument of type wint_t, the value is representable as a wchar_t or equals the value of WEOF. If this argument has any other value, the behavior is undefined.
The behavior of these functions shall be affected by the LC_CTYPE category of the current locale.
Inclusion of the <wctype.h> header may make visible all symbols from the headers <ctype.h>, <stdarg.h>, <stddef.h>, <stdio.h>, <stdlib.h>, <string.h>, <time.h>, and <wchar.h>.
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.
int iswalnum(wint_t); int iswalnum_l(wint_t, locale_t); int iswalpha(wint_t); int iswalpha_l(wint_t, locale_t); int iswblank(wint_t); int iswblank_l(wint_t, locale_t); int iswcntrl(wint_t); int iswcntrl_l(wint_t, locale_t); int iswctype(wint_t, wctype_t); int iswctype_l(wint_t, wctype_t, locale_t); int iswdigit(wint_t); int iswdigit_l(wint_t, locale_t); int iswgraph(wint_t); int iswgraph_l(wint_t, locale_t); int iswlower(wint_t); int iswlower_l(wint_t, locale_t); int iswprint(wint_t); int iswprint_l(wint_t, locale_t); int iswpunct(wint_t); int iswpunct_l(wint_t, locale_t); int iswspace(wint_t); int iswspace_l(wint_t, locale_t); int iswupper(wint_t); int iswupper_l(wint_t, locale_t); int iswxdigit(wint_t); int iswxdigit_l(wint_t, locale_t); wint_t towctrans(wint_t, wctrans_t); wint_t towctrans_l(wint_t, wctrans_t, locale_t); wint_t towlower(wint_t); wint_t towlower_l(wint_t, locale_t); wint_t towupper(wint_t); wint_t towupper_l(wint_t, locale_t); wctrans_t wctrans(const char *); wctrans_t wctrans_l(const char *, locale_t); wctype_t wctype(const char *); wctype_t wctype_l(const char *, locale_t);
The following sections are informative.
The System Interfaces volume of POSIX.1-2017, Section 2.2, The Compilation Environment, iswalnum(), iswalpha(), iswblank(), iswcntrl(), iswctype(), iswdigit(), iswgraph(), iswlower(), iswprint(), iswpunct(), iswspace(), iswupper(), iswxdigit(), setlocale(), towctrans(), towlower(), towupper(), wctrans(), wctype()
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