ALARM(3)

ALARM(3) | 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 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.

April 19, 1994 | NetBSD 8.0