alarm(2) System Calls Manual alarm(2)
NAME
alarm - set an alarm clock for delivery of a signal
LIBRARY
Standard C library (libc, -lc)
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.
STANDARDS
POSIX.1-2008.
HISTORY
POSIX.1-2001, SVr4, 4.3BSD.
NOTES
alarm() and setitimer(2) share the same timer; calls to one will inter-
fere with use of the other.
Alarms created by alarm() are preserved across execve(2) and are not in-
herited 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.
SEE ALSO
gettimeofday(2), pause(2), select(2), setitimer(2), sigaction(2), sig-
nal(2), timer_create(2), timerfd_create(2), sleep(3), time(7)
Linux man-pages 6.9.1 2024-05-02 alarm(2)
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