ALARM(3)               FreeBSD Library Functions Manual               ALARM(3)

NAME

     alarm - set signal timer alarm

LIBRARY

     Standard C Library (libc, -lc)

SYNOPSIS

     #include <unistd.h>

     unsigned int
     alarm(unsigned int seconds);

DESCRIPTION

     This interface is made obsolete by setitimer(2).

     The alarm() function sets a timer to deliver the signal SIGALRM to the
     calling process after the specified number of seconds.  If an alarm has
     already been set with alarm() but has not been delivered, another call to
     alarm() will supersede the prior call.  The request alarm(0) voids the
     current alarm and the signal SIGALRM will not be delivered.

     Due to setitimer(2) restriction the maximum number of seconds allowed is
     100,000,000.

RETURN VALUES

     The return value of alarm() is the amount of time left on the timer from
     a previous call to alarm().  If no alarm is currently set, the return
     value is 0.

SEE ALSO

     setitimer(2), sigaction(2), sigsuspend(2), signal(3), sleep(3),
     ualarm(3), usleep(3)

HISTORY

     An alarm() system call appeared in the Programmer's Workbench (PWB/UNIX)
     and was ported to Version 7 AT&T UNIX.  For 4.1cBSD, it was reimplemented
     as a wrapper around the setitimer(2) system call.

FreeBSD 15.1-STABLE-HBSD         April 2, 2022                        ALARM(3)