What does a dot before the variable name in struct mean?

Question

looking at the linux kernel source, I found this:

static struct tty_operations serial_ops = {   .open = tiny_open,   .close = tiny_close,   .write = tiny_write,   .write_room = tiny_write_room,   .set_termios = tiny_set_termios, }; 

I've never seen such a notation in C. Why is there a dot before the variable name?

Answer 1

This is a Designated Initializer, which is syntax added for C99. Relevant excerpt:

In a structure initializer, specify the name of a field to initialize with ‘.fieldname =’ before the element value. For example, given the following structure,

struct point { int x, y; };  

the following initialization

struct point p = { .y = yvalue, .x = xvalue };  

is equivalent to

struct point p = { xvalue, yvalue };