size?(p1)
public
Returns nil if file_name doesn’t exist or has zero
size, the size of the file otherwise.
file_name can be an IO object.
static VALUE
rb_file_size_p(VALUE obj, VALUE fname)
{
struct stat st;
if (rb_stat(fname, &st) < 0) return Qnil;
if (st.st_size == 0) return Qnil;
return OFFT2NUM(st.st_size);
}