NAME
alarm —
set signal timer alarm
SYNOPSIS
#include
<unistd.h>
unsigned int
alarm(unsigned
int seconds);
DESCRIPTION
The
alarm()
function waits a count of seconds before asserting the
terminating signal SIGALRM. When the signal has
successfully been caught, alarm() returns the amount
of time left on the clock. The maximum number of
seconds allowed is 100000000.
If an alarm has been set with
alarm(),
another call to alarm() will supersede the prior
call. The request alarm(0)
voids the current alarm.
RETURN VALUES
If the call succeeds, any time left remaining from a previous call is returned. If an error occurs, the value -1 is returned, and a more precise error code is placed in the global variable errno.
SEE ALSO
setitimer(2), sigaction(2), sigsuspend(2), signal(3), sleep(3), ualarm(3)
STANDARDS
The alarm() function conforms to
IEEE Std 1003.1-2008 (“POSIX.1”).
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.