TOUPPER(3) Linux Programmer's Manual TOUPPER(3)NAME
toupper, tolower - convert letter to upper or lower case
SYNOPSIS
#include <ctype.h>
int toupper(int c);
int tolower(int c);
DESCRIPTIONtoupper() 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 func‐
tions is undefined.
RETURN VALUE
The value returned is that of the converted letter, or c if the conver‐
sion 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
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 corre‐
sponding uppercase equivalent; the German sharp s is one example.
SEE ALSOisalpha(3), setlocale(3), towlower(3), towupper(3), locale(7)COLOPHON
This page is part of release 3.58 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/.
GNU 2014-01-22 TOUPPER(3)
