ALARM(2) Linux Programmer s Manual ALARM(2)

NAME alarm - set an alarm clock for delivery of a signal

SYNOPSIS #include <unistd.h>

unsigned int alarm(unsigned int seconds);

DESCRIPTION alarm() arranges for a SIGALRM signal to be delivered to the calling process in seconds seconds.

If seconds is zero, no new alarm() is scheduled.

In any event any previously set alarm() is canceled.

RETURN VALUE alarm() returns the number of seconds remaining until any previously scheduled alarm was due to be delivered, or zero if there was no previ- ously scheduled alarm.


NOTES alarm() and setitimer(2) share the same timer; calls to one will inter- fere with use of the other.

sleep(3) may be implemented using SIGALRM; mixing calls to alarm() and sleep(3) is a bad idea.

Scheduling delays can, as ever, cause the execution of the process to be delayed by an arbitrary amount of time.

SEE ALSO gettimeofday(2), pause(2), select(2), setitimer(2), sigaction(2), sig- nal(2), sleep(3), time(7)

COLOPHON This page is part of release 3.22 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at

Linux 2008-06-12 ALARM(2)