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NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | STANDARDS | HISTORY | NOTES | SEE ALSO | COLOPHON |
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alarm(2) System Calls Manual alarm(2)
alarm - set an alarm clock for delivery of a signal
Standard C library (libc, -lc)
#include <unistd.h>
unsigned int alarm(unsigned int seconds);
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.
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.
POSIX.1-2008.
POSIX.1-2001, SVr4, 4.3BSD.
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.
gettimeofday(2), pause(2), select(2), setitimer(2), sigaction(2),
signal(2), timer_create(2), timerfd_create(2), sleep(3), time(7)
This page is part of the man-pages (Linux kernel and C library
user-space interface documentation) project. Information about
the project can be found at
⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report
for this manual page, see
⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
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2025-02-02. If you discover any rendering problems in this HTML
version of the page, or you believe there is a better or more up-
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part of the original manual page), send a mail to
man-pages@man7.org
Linux man-pages 6.10 2024-07-23 alarm(2)
Pages that refer to this page: tload(1), fork(2), getitimer(2), seccomp(2), sigaction(2), signal(2), syscalls(2), sleep(3), ualarm(3), usleep(3), systemd.exec(5), signal(7), signal-safety(7), time(7)
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HTML rendering created 2025-02-02 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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