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 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 100000000.
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.