mirror of https://github.com/mkerrisk/man-pages
89 lines
2.6 KiB
Groff
89 lines
2.6 KiB
Groff
.\" Hey Emacs! This file is -*- nroff -*- source.
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.\"
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.\" This manpage is Copyright (C) 1992 Drew Eckhardt;
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.\" 1993 Michael Haardt, Ian Jackson.
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.\"
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.\" Permission is granted to make and distribute verbatim copies of this
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.\" manual provided the copyright notice and this permission notice are
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.\" preserved on all copies.
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.\"
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.\" Permission is granted to copy and distribute modified versions of this
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.\" manual under the conditions for verbatim copying, provided that the
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.\" entire resulting derived work is distributed under the terms of a
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.\" permission notice identical to this one.
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.\"
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.\" Since the Linux kernel and libraries are constantly changing, this
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.\" manual page may be incorrect or out-of-date. The author(s) assume no
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.\" responsibility for errors or omissions, or for damages resulting from
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.\" the use of the information contained herein. The author(s) may not
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.\" have taken the same level of care in the production of this manual,
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.\" which is licensed free of charge, as they might when working
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.\" professionally.
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.\"
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.\" Formatted or processed versions of this manual, if unaccompanied by
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.\" the source, must acknowledge the copyright and authors of this work.
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.\"
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.\" Modified Wed Jul 21 19:42:57 1993 by Rik Faith <faith@cs.unc.edu>
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.\" Modified Sun Jul 21 21:25:26 1996 by Andries Brouwer <aeb@cwi.nl>
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.\" Modified Wed Nov 6 03:46:05 1996 by Eric S. Raymond <esr@thyrsus.com>
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.\"
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.TH ALARM 2 1993-07-21 Linux "Linux Programmer's Manual"
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.SH NAME
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alarm \- set an alarm clock for delivery of a signal
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.SH SYNOPSIS
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.nf
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.B #include <unistd.h>
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.sp
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.BI "unsigned int alarm(unsigned int " seconds );
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.fi
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.SH DESCRIPTION
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.BR alarm ()
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arranges for a
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.B SIGALRM
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signal to be delivered to the process in
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.I seconds
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seconds.
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If
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.I seconds
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is zero, no new
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.BR alarm ()
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is scheduled.
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In any event any previously set
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.BR alarm ()
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is cancelled.
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.SH "RETURN VALUE"
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.BR alarm ()
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returns the number of seconds remaining until any previously scheduled
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alarm was due to be delivered, or zero if there was no previously
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scheduled alarm.
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.SH NOTES
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.BR alarm ()
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and
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.BR setitimer ()
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share the same timer; calls to one will interfere with use of the
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other.
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.PP
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.BR sleep ()
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may be implemented using
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.BR SIGALRM ;
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mixing calls to
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.BR alarm ()
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and
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.BR sleep ()
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is a bad idea.
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Scheduling delays can, as ever, cause the execution of the process to
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be delayed by an arbitrary amount of time.
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.SH "CONFORMING TO"
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SVr4, POSIX.1-2001, 4.3BSD
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.SH "SEE ALSO"
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.BR gettimeofday (2),
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.BR pause (2),
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.BR select (2),
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.BR setitimer (2),
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.BR sigaction (2),
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.BR signal (2),
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.BR sleep (3)
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