ualarm - set an alarm clock for delivery of a signal
int ualarm(int useconds);
ualarm arranges for a SIGALRM signal to be delivered to the
process in useconds micro seconds.
If useconds is zero, no new alarm is scheduled.
In any event any previously set alarm is cancelled.
ualarm returns the number of microseconds seconds remaining
until any previously scheduled alarm was due to be delivered, or
zero if there was no previously scheduled alarm.