alarm (2)
Leading comments
This manpage is Copyright (C) 1992 Drew Eckhardt;
and Copyright (C) 1993 Michael Haardt, Ian Jackson.
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NAME
alarm - set an alarm clock for delivery of a signalSYNOPSIS
#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 previously scheduled alarm.CONFORMING TO
POSIX.1-2001, POSIX.1-2008, SVr4, 4.3BSD.NOTES
alarm() and setitimer(2) share the same timer; calls to one will interfere with use of the other.Alarms created by alarm() are preserved across execve(2) and are not inherited by children created via fork(2).
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.