a simple function to duplicate string and lower it.

strdup_lower.c

char* strdup_lower(char* str) {
	char *b;
	char *s;
	char *buf;
	
	errno = 0;
	buf = strdup(str);
	if (!buf)
		return NULL;

	b = buf;
	s = str;
	while(*b) {
		*b++ = tolower(*s++);
	}

	errno = 0;
	return buf;
}