redhat man page for alarm

ALARM(2)						     Linux Programmer's Manual							  ALARM(2)

NAME
       alarm - set an alarm clock for delivery of a signal

SYNOPSIS
       #include <unistd.h>

       unsigned int alarm(unsigned int seconds);

DESCRIPTION
       alarm arranges for a SIGALRM signal to be delivered to the process in seconds seconds.

       If seconds is zero, no new alarm is scheduled.

       In any event any previously set alarm is cancelled.

RETURN VALUE
       alarm  returns the number of seconds remaining until any previously scheduled alarm was due to be delivered, or zero if there was no previ-
       ously scheduled alarm.

NOTES
       alarm and setitimer share the same timer; calls to one will interfere with use of the other.

       sleep() may be implemented using SIGALRM; mixing calls to alarm() and sleep() is a bad idea.

       Scheduling delays can, as ever, cause the execution of the process to be delayed by an arbitrary amount of time.

CONFORMING TO
       SVr4, SVID, POSIX, X/OPEN, BSD 4.3

SEE ALSO
       setitimer(2), signal(2), sigaction(2), gettimeofday(2), select(2), pause(2), sleep(3)

Linux								    1993-07-21								  ALARM(2)