преобразовать верхний или нижний регистр (convert uppercase or lowercase)
Имя (Name)
toupper, tolower, toupper_l, tolower_l - convert uppercase or
lowercase
Синопсис (Synopsis)
#include <ctype.h>
int toupper(int c);
int tolower(int c);
int toupper_l(int c, locale_t locale);
int tolower_l(int c, locale_t locale);
Feature Test Macro Requirements for glibc (see
feature_test_macros(7)):
toupper_l(), tolower_l():
Since glibc 2.10:
_XOPEN_SOURCE >= 700
Before glibc 2.10:
_GNU_SOURCE
Описание (Description)
These functions convert lowercase letters to uppercase, and vice
versa.
If c is a lowercase letter, toupper() returns its uppercase
equivalent, if an uppercase representation exists in the current
locale. Otherwise, it returns c. The toupper_l() function
performs the same task, but uses the locale referred to by the
locale handle locale.
If c is an uppercase letter, tolower() returns its lowercase
equivalent, if a lowercase representation exists in the current
locale. Otherwise, it returns c. The tolower_l() function
performs the same task, but uses the locale referred to by the
locale handle locale.
If c is neither an unsigned char value nor EOF, the behavior of
these functions is undefined.
The behavior of toupper_l() and tolower_l() is undefined if
locale is the special locale object LC_GLOBAL_LOCALE (see
duplocale(3)) or is not a valid locale object handle.
Возвращаемое значение (Return value)
The value returned is that of the converted letter, or c if the
conversion was not possible.
Атрибуты (Attributes)
For an explanation of the terms used in this section, see
attributes(7).
┌──────────────────────────────────────┬───────────────┬─────────┐
│Interface │ Attribute │ Value │
├──────────────────────────────────────┼───────────────┼─────────┤
│toupper(), tolower(), toupper_l(), │ Thread safety │ MT-Safe │
│tolower_l() │ │ │
└──────────────────────────────────────┴───────────────┴─────────┘
Стандарты (Conforming to)
toupper(), tolower(): C89, C99, 4.3BSD, POSIX.1-2001,
POSIX.1-2008.
toupper_l(), tolower_l(): POSIX.1-2008.
Примечание (Note)
The standards require that the argument c for these functions is
either EOF or a value that is representable in the type unsigned
char. If the argument c is of type char, it must be cast to
unsigned char, as in the following example:
char c;
...
res = toupper((unsigned char) c);
This is necessary because char may be the equivalent signed char,
in which case a byte where the top bit is set would be sign
extended when converting to int, yielding a value that is outside
the range of unsigned char.
The details of what constitutes an uppercase or lowercase letter
depend on the locale. For example, the default "C" locale does
not know about umlauts, so no conversion is done for them.
In some non-English locales, there are lowercase letters with no
corresponding uppercase equivalent; the German sharp s is one
example.
Смотри также (See also)
isalpha(3), newlocale(3), setlocale(3), towlower(3), towupper(3),
uselocale(3), locale(7)
