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 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 unde‐
       fined.

       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 possi‐
       ble.

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 3.74 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 http://www.kernel.org/doc/man-pages/.



GNU                                         2014-03-18                                 TOUPPER(3)