ALARM(2) - man page online | system calls

Set an alarm clock for delivery of a signal.

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, 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.
SEE ALSO gettimeofday(2), pause(2), select(2), setitimer(2), sigaction(2), signal(2), sleep(3), time(7)
COLOPHON This page is part of release 4.04 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
Linux 2015-08-08 ALARM(2)
This manual Reference Other manuals
alarm(2) referred by fork(2) | getitimer(2) | IO::Async::Loop(3pm) | Mail::SpamAssassin::Timeout(3pm) | Modem::Vgetty(3pm) | ObjCmdWrite(3tclx) | randtype(1) | seccomp(2) | signal(2) | signal(7) | sleep(3) | snmp_alarm(3) | Sys::SigAction(3pm) | syscalls(2) | time(7) | Time::Out(3pm) | tload(1) | ualarm(3) | usleep(3)
refer to execve(2) | fork(2) | getitimer(2) | gettimeofday(2) | pause(2) | select(2) | sigaction(2) | signal(2) | sleep(3) | time(7)