NAME

       alarm - set an alarm clock for delivery of a signal

LIBRARY

       Standard C library (libc, -lc)

SYNOPSIS

       #include <unistd.h>

       unsigned int alarm(unsigned int seconds);

DESCRIPTION

       alarm() arranges for a SIGALRM signal to be delivered to the calling process in seconds seconds.

       If seconds is zero, any pending alarm is canceled.

       In any event any previously set alarm() is canceled.

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 previously scheduled alarm.

STANDARDS

       POSIX.1-2008.

HISTORY

       POSIX.1-2001, SVr4, 4.3BSD.

NOTES

       alarm() and setitimer(2) share the same timer; calls to one will interfere with use of the other.

       Alarms created by alarm() are preserved across execve(2) and are not inherited by  children  created  via
       fork(2).

       sleep(3) may be implemented using SIGALRM; mixing calls to alarm() and sleep(3) is a bad idea.

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

SEE ALSO

       gettimeofday(2),   pause(2),   select(2),   setitimer(2),   sigaction(2),   signal(2),   timer_create(2),
       timerfd_create(2), sleep(3), time(7)