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alarm
<html> <head> <title>alarm</title> <META NAME="KEYWORDS" CONTENT="alarm"> </head> <body BGCOLOR="#ffffff" LINK="#0000ff" VLINK="#0000ff" ALINK="#0000ff" TEXT="#000000"> <center> <h1><b>alarm</b></h1></center> <PRE> <STRONG><A HREF="/man2/ALARM">ALARM(2)</A></STRONG> Linux Programmer's Manual <STRONG><A HREF="/man2/ALARM">ALARM(2)</A></STRONG> 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, any pending alarm is canceled. 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. CONFORMING TO POSIX.1-2001, POSIX.1-2008, SVr4, 4.3BSD. NOTES alarm() and <STRONG><A HREF="/man2/setitimer">setitimer(2)</A></STRONG> share the same timer; calls to one will inter- fere with use of the other. Alarms created by alarm() are preserved across <STRONG><A HREF="/man2/execve">execve(2)</A></STRONG> and are not inherited by children created via <STRONG><A HREF="/man2/fork">fork(2)</A></STRONG>. <STRONG><A HREF="/man3/sleep">sleep(3)</A></STRONG> may be implemented using SIGALRM; mixing calls to alarm() and <STRONG><A HREF="/man3/sleep">sleep(3)</A></STRONG> 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 <STRONG><A HREF="/man2/gettimeofday">gettimeofday(2)</A></STRONG>, <STRONG><A HREF="/man2/pause">pause(2)</A></STRONG>, <STRONG><A HREF="/man2/select">select(2)</A></STRONG>, <STRONG><A HREF="/man2/setitimer">setitimer(2)</A></STRONG>, <STRONG><A HREF="/man2/sigaction">sigaction(2)</A></STRONG>, sig- <STRONG><A HREF="/man2/nal">nal(2)</A></STRONG>, <STRONG><A HREF="/man2/timer_create">timer_create(2)</A></STRONG>, <STRONG><A HREF="/man2/timerfd_create">timerfd_create(2)</A></STRONG>, <STRONG><A HREF="/man3/sleep">sleep(3)</A></STRONG>, <STRONG><A HREF="/man7/time">time(7)</A></STRONG> COLOPHON This page is part of release 5.05 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at https://www.kernel.org/doc/man-pages/. Linux 2017-05-03 <STRONG><A HREF="/man2/ALARM">ALARM(2)</A></STRONG></PRE> <center> <h6>Man Pages Copyright Respective Owners. Site Copyright (C) 1994 - 2025 <a href="http://www.he.net">Hurricane Electric</a>. All Rights Reserved.</h6></center> </body> </html>