NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ATTRIBUTES | CONFORMING TO | NOTES | SEE ALSO | COLOPHON

TOUPPER(3)                Linux Programmer's Manual               TOUPPER(3)

NAME         top

       toupper,  tolower, toupper_l, tolower_l - convert uppercase or lower‐
       case

SYNOPSIS         top

       #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

DESCRIPTION         top

       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.

RETURN VALUE         top

       The value returned is that of the converted letter, or c if the
       conversion was not possible.

ATTRIBUTES         top

       For an explanation of the terms used in this section, see
       attributes(7).

       ┌─────────────────────────┬───────────────┬─────────┐
       │Interface                Attribute     Value   │
       ├─────────────────────────┼───────────────┼─────────┤
       │toupper(), tolower(),    │ Thread safety │ MT-Safe │
       │toupper_l(), tolower_l() │               │         │
       └─────────────────────────┴───────────────┴─────────┘

CONFORMING TO         top

       toupper(), tolower(): C89, C99, 4.3BSD, POSIX.1-2001, POSIX.1-2008.

       toupper_l(), tolower_l(): POSIX.1-2008.

NOTES         top

       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.

SEE ALSO         top

       isalpha(3), newlocale(3), setlocale(3), towlower(3), towupper(3),
       uselocale(3), locale(7)

COLOPHON         top

       This page is part of release 4.08 of the Linux man-pages project.  A
       description of the project, information about reporting bugs, and the
       latest version of this page, can be found at
       https://www.kernel.org/doc/man-pages/.

GNU                              2016-10-08                       TOUPPER(3)