#include <ctype.h>
The <ctype.h> header shall define the locale_t type as described in <locale.h>, representing a locale object.
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 isalnum(int); int isalnum_l(int, locale_t); int isalpha(int); int isalpha_l(int, locale_t); int isascii(int); int isblank(int); int isblank_l(int, locale_t); int iscntrl(int); int iscntrl_l(int, locale_t); int isdigit(int); int isdigit_l(int, locale_t); int isgraph(int); int isgraph_l(int, locale_t); int islower(int); int islower_l(int, locale_t); int isprint(int); int isprint_l(int, locale_t); int ispunct(int); int ispunct_l(int, locale_t); int isspace(int); int isspace_l(int, locale_t); int isupper(int); int isupper_l(int, locale_t); int isxdigit(int); int isxdigit_l(int, locale_t); int toascii(int); int tolower(int); int tolower_l(int, locale_t); int toupper(int); int toupper_l(int, locale_t);
The <ctype.h> header shall define the following as macros:
int _toupper(int); int _tolower(int);
The following sections are informative.
The System Interfaces volume of POSIX.1-2017, Section 2.2, The Compilation Environment, isalnum(), isalpha(), isascii(), isblank(), iscntrl(), isdigit(), isgraph(), islower(), isprint(), ispunct(), isspace(), isupper(), isxdigit(), mblen(), mbstowcs(), mbtowc(), setlocale(), toascii(), tolower(), _tolower(), toupper(), _toupper(), wcstombs(), wctomb()
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