`islower.3p` ( 3 )

тест на строчную букву (test for a lowercase letter)

Пролог (Prolog)

This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.

Имя (Name)

islower, islower_l — test for a lowercase letter

Синопсис (Synopsis)

#include <ctype.h>

int islower(int c); int islower_l(int c, locale_t locale);

Описание (Description)

For islower(): The functionality described on this reference page is aligned with the ISO C standard. Any conflict between the requirements described here and the ISO C standard is unintentional. This volume of POSIX.1‐2017 defers to the ISO C standard.

The islower() and islower_l() functions shall test whether c is a character of class lower in the current locale, or in the locale represented by locale, respectively; see the Base Definitions volume of POSIX.1‐2017, Chapter 7, Locale.

The c argument is an int, the value of which the application shall ensure is a character representable as an unsigned char or equal to the value of the macro EOF. If the argument has any other value, the behavior is undefined.

The behavior is undefined if the locale argument to islower_l() is the special locale object LC_GLOBAL_LOCALE or is not a valid locale object handle.

Возвращаемое значение (Return value)

The islower() and islower_l() functions shall return non-zero if c is a lowercase letter; otherwise, they shall return 0.

Ошибки (Error)

No errors are defined.

The following sections are informative.

Примеры (Examples)

Testing for a Lowercase Letter
       Two examples follow, the first using islower(), the second using
       multiple concurrent locales and islower_l().

       The examples test whether the value is a lowercase letter, based
       on the current locale, then use it as part of a key value.

           /* Example 1 -- using islower() */
           #include <ctype.h>
           #include <stdlib.h>
           #include <locale.h>
           ...
           char *keystr;
           int elementlen, len;
           unsigned char c;
           ...
           setlocale(LC_ALL, "");
           ...
           len = 0;
           while (len < elementlen) {
               c = (unsigned char) (rand() % 256);
           ...
               if (islower(c))
                   keystr[len++] = c;
               }
           ...

           /* Example 2 -- using islower_l() */
           #include <ctype.h>
           #include <stdlib.h>
           #include <locale.h>
           ...
           char *keystr;
           int elementlen, len;
           unsigned char c;
           ...
           locale_t loc = newlocale (LC_ALL_MASK, "", (locale_t) 0);
           ...
           len = 0;
           while (len < elementlen) {
               c = (unsigned char) (rand() % 256);
           ...
               if (islower_l(c, loc))
                   keystr[len++] = c;
               }
           ...

Использование в приложениях (Application usage)

To ensure applications portability, especially across natural languages, only these functions and the functions in the reference pages listed in the SEE ALSO section should be used for character classification.

Обоснование (Rationale)

None.

Будущие направления (Future directions)