alarm seconds
Instructs the system to send a SIGALRM signal in
the specified number of seconds. This is a floating point number, so
fractions of a second may be specified. If seconds is 0.0, any
previous alarm request is canceled. Only one alarm at a time may be
active; the command returns the number of seconds left in the previous
alarm. On systems without the setitimer system call,
seconds is rounded up to an even number of seconds.