_tolower() — Translate uppercase characters to lowercase

Standards

Standards / Extensions	C or C++	Dependencies
XPG4 XPG4.2 Single UNIX Specification, Version 3	both

#define _XOPEN_SOURCE
#include <ctype.h>

int _tolower(int c);

The _tolower() macro is equivalent to tolower(c) except that the argument c must be an uppercase letter.

_tolower() returns the lowercase letter corresponding to the argument passed.