replace(str, fill, start, stop)
{
	local out;
	local sum;

	out = galloc(strlen(str) + strlen(fill) - (stop - start) + 1);
	if (out == NULL)
		return (NULL);
	strncpy(out, str, start);
	strncpy(out + start, fill, strlen(fill));
	sum = start + strlen(fill);
	strncpy(out + sum, str + stop, strlen(str) - stop);
	[out + sum + strlen(str) - stop] = 0;
	return (out);
}