mirror of https://github.com/mkerrisk/man-pages
179 lines
4.8 KiB
Groff
179 lines
4.8 KiB
Groff
.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved
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.TH "SLEEP" 1P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
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.\" sleep
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.SH PROLOG
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This manual page is part of the POSIX Programmer's Manual.
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The Linux implementation of this interface may differ (consult
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the corresponding Linux manual page for details of Linux behavior),
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or the interface may not be implemented on Linux.
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.SH NAME
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sleep \- suspend execution for an interval
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.SH SYNOPSIS
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.LP
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\fBsleep\fP \fItime\fP
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.SH DESCRIPTION
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.LP
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The \fIsleep\fP utility shall suspend execution for at least the integral
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number of seconds specified by the \fItime\fP
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operand.
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.SH OPTIONS
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.LP
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None.
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.SH OPERANDS
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.LP
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The following operand shall be supported:
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.TP 7
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\fItime\fP
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A non-negative decimal integer specifying the number of seconds for
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which to suspend execution.
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.sp
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.SH STDIN
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.LP
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Not used.
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.SH INPUT FILES
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.LP
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None.
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.SH ENVIRONMENT VARIABLES
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.LP
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The following environment variables shall affect the execution of
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\fIsleep\fP:
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.TP 7
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\fILANG\fP
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Provide a default value for the internationalization variables that
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are unset or null. (See the Base Definitions volume of
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IEEE\ Std\ 1003.1-2001, Section 8.2, Internationalization Variables
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for
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the precedence of internationalization variables used to determine
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the values of locale categories.)
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.TP 7
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\fILC_ALL\fP
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If set to a non-empty string value, override the values of all the
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other internationalization variables.
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.TP 7
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\fILC_CTYPE\fP
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Determine the locale for the interpretation of sequences of bytes
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of text data as characters (for example, single-byte as
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opposed to multi-byte characters in arguments).
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.TP 7
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\fILC_MESSAGES\fP
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Determine the locale that should be used to affect the format and
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contents of diagnostic messages written to standard
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error.
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.TP 7
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\fINLSPATH\fP
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Determine the location of message catalogs for the processing of \fILC_MESSAGES
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\&.\fP
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.sp
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.SH ASYNCHRONOUS EVENTS
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.LP
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If the \fIsleep\fP utility receives a SIGALRM signal, one of the following
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actions shall be taken:
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.IP " 1." 4
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Terminate normally with a zero exit status.
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.LP
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.IP " 2." 4
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Effectively ignore the signal.
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.LP
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.IP " 3." 4
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Provide the default behavior for signals described in the ASYNCHRONOUS
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EVENTS section of \fIUtility Description Defaults\fP . This could
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include terminating with a non-zero exit
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status.
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.LP
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.LP
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The \fIsleep\fP utility shall take the standard action for all other
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signals.
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.SH STDOUT
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.LP
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Not used.
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.SH STDERR
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.LP
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The standard error shall be used only for diagnostic messages.
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.SH OUTPUT FILES
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.LP
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None.
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.SH EXTENDED DESCRIPTION
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.LP
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None.
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.SH EXIT STATUS
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.LP
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The following exit values shall be returned:
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.TP 7
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\ 0
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The execution was successfully suspended for at least \fItime\fP seconds,
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or a SIGALRM signal was received. See the
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ASYNCHRONOUS EVENTS section.
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.TP 7
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>0
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An error occurred.
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.sp
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.SH CONSEQUENCES OF ERRORS
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.LP
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Default.
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.LP
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\fIThe following sections are informative.\fP
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.SH APPLICATION USAGE
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.LP
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None.
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.SH EXAMPLES
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.LP
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The \fIsleep\fP utility can be used to execute a command after a certain
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amount of time, as in:
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.sp
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.RS
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.nf
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\fB(sleep 105;\fP \fIcommand\fP\fB) &
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\fP
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.fi
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.RE
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.LP
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or to execute a command every so often, as in:
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.sp
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.RS
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.nf
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\fBwhile true
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do
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\fP \fIcommand\fP \fB sleep 37
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done
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\fP
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.fi
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.RE
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.SH RATIONALE
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.LP
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The exit status is allowed to be zero when \fIsleep\fP is interrupted
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by the SIGALRM signal because most implementations of
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this utility rely on the arrival of that signal to notify them that
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the requested finishing time has been successfully attained.
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Such implementations thus do not distinguish this situation from the
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successful completion case. Other implementations are allowed
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to catch the signal and go back to sleep until the requested time
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expires or to provide the normal signal termination
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procedures.
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.LP
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As with all other utilities that take integral operands and do not
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specify subranges of allowed values, \fIsleep\fP is required
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by this volume of IEEE\ Std\ 1003.1-2001 to deal with \fItime\fP requests
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of up to 2147483647 seconds. This may mean that
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some implementations have to make multiple calls to the delay mechanism
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of the underlying operating system if its argument range is
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less than this.
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.SH FUTURE DIRECTIONS
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.LP
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None.
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.SH SEE ALSO
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.LP
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\fIwait\fP, the System Interfaces volume of IEEE\ Std\ 1003.1-2001,
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\fIalarm\fP(), \fIsleep\fP()
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.SH COPYRIGHT
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Portions of this text are reprinted and reproduced in electronic form
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from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
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-- Portable Operating System Interface (POSIX), The Open Group Base
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Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
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Electrical and Electronics Engineers, Inc and The Open Group. In the
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event of any discrepancy between this version and the original IEEE and
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The Open Group Standard, the original IEEE and The Open Group Standard
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is the referee document. The original Standard can be obtained online at
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http://www.opengroup.org/unix/online.html .
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