tolower

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



NAME
       toupper, tolower, toupper_l, tolower_l - convert uppercase or lowercase

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

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.

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

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

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

NOTES
       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.

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

COLOPHON
       This page is part of release 5.02 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                               2017-09-15                        TOUPPER(3)