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 9.0