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NAME

       toupper, tolower - convert letter to upper or lower case

SYNOPSIS

       #include <ctype.h>

       int toupper(int c);
       int tolower(int c);

DESCRIPTION

       toupper() converts the letter c to upper case, if possible.

       tolower() converts the letter c to lower case, if possible.

       If  c  is  not  an  unsigned  char value, or EOF, the behavior of these
       functions is undefined.

RETURN VALUE

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

CONFORMING TO

       C89, C99, 4.3BSD.

BUGS

       The details of what constitutes an uppercase or lowercase letter depend
       on the current 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), setlocale(3), towlower(3), towupper(3), locale(7)

COLOPHON

       This  page  is  part of release 3.21 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/.