Hands-On System Programming with Linux

Waiting forever or until a signal arrives

Often, one would like to wait forever, or until a signal arrives. One way to do so is the very simple, but very bad, terribly expensive spin on the CPU code such as this:

while (1);

Ugh! That's just ugly: please do not write code like that!

Slightly better, but still quite off, is this:

while (1)    sleep(1);

The pause can be used to effectively and efficiently set up a useful wait forever or until I receive any signal semantic, as follows:

while (1)    (void)pause();

This semantic is very useful for this wait forever or until I receive any signal situation, as it's inexpensive (hardly any CPU usage as the pause(2) has the caller immediately go to sleep), and get unblocked only when a signal arrives. ...