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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 a 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

   Multithreading (see pthreads(7))
       The  toupper() and tolower() functions are thread-safe with exceptions.
       These functions can be safely used in  multithreaded  applications,  as
       long  as  setlocale(3)  is not called to change the locale during their
       execution.

CONFORMING TO

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

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

NOTES

       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),  uselocale(3),  towlower(3),
       towupper(3), locale(7)

COLOPHON

       This page is part of release 3.65 of the Linux  man-pages  project.   A
       description  of  the project, and information about reporting bugs, can
       be found at http://www.kernel.org/doc/man-pages/.



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