tolower, tolower_l—translate characters to lowercaseSynopsis
#include <ctype.h> int tolower(int c); int _tolower(int c); #include <ctype.h> int tolower_l(int c, locale_t locale);
Description
tolower is a macro which converts uppercase characters to lowercase,
leaving all other characters unchanged. It is only defined when
c is an integer in the range EOF to 255.
tolower_l is like tolower but performs the function based on the
locale specified by the locale object locale. If locale is
LC_GLOBAL_LOCALE or not a valid locale object, the behaviour is undefined.
You can use a compiled subroutine instead of the macro definition by
undefining this macro using ‘#undef tolower’ or ‘#undef tolower_l’.
_tolower performs the same conversion as tolower, but should
only be used when c is known to be an uppercase character (A–Z).
Returns
tolower, tolower_l return the lowercase equivalent of c when
c is an uppercase character, and c otherwise.
_tolower returns the lowercase equivalent of c when it is a
character between A and Z. If c is not one of these
characters, the behaviour of _tolower is undefined.
Portability
tolower is ANSI C. _tolower is not recommended for portable programs.
tolower_l is POSIX-1.2008.
No supporting OS subroutines are required.