NAME
alarm —
set signal timer alarm
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
#include <unistd.h>
unsigned int
alarm(
unsigned
int seconds);
DESCRIPTION
The
alarm() function sets a timer to deliver the signal
SIGALRM
to the calling process
seconds after the call to
alarm(). 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. The maximum number
of
seconds allowed is 2147483647.
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. If there is an error setting the timer,
alarm() returns ((unsigned int) -1).
SEE ALSO
setitimer(2),
sigaction(2),
sigsuspend(2),
signal(3),
sigvec(3),
sleep(3),
ualarm(3),
usleep(3)
STANDARDS
The
alarm() function conforms to
IEEE Std
1003.1-1990 (“POSIX.1”).
HISTORY
An
alarm() function appeared in
Version 7 AT&T UNIX.