toupper, tolower, toupper_l, tolower_l - convert uppercase or lowercase
#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)):
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.
The value returned is that of the converted letter, or c
if the conversion was not possible.