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sleep(P) sleep(P)
NAME
sleep - suspend execution for an interval
SYNOPSIS
sleep time
DESCRIPTION
The sleep utility shall suspend execution for at least
the integral number of seconds specified by the time op-
erand.
OPTIONS
None.
OPERANDS
The following operand shall be supported:
time A non-negative decimal integer specifying the
number of seconds for which to suspend execution.
STDIN
Not used.
INPUT FILES
None.
ENVIRONMENT VARIABLES
The following environment variables shall affect the
execution of sleep:
LANG Provide a default value for the internationaliza-
tion variables that are unset or null. (See the
Base Definitions volume of IEEE Std 1003.1-2001,
Section 8.2, Internationalization Variables for
the precedence of internationalization variables
used to determine the values of locale cate-
gories.)
LC_ALL If set to a non-empty string value, override the
values of all the other internationalization
variables.
LC_CTYPE
Determine the locale for the interpretation of
sequences of bytes of text data as characters
(for example, single-byte as opposed to multi-
byte characters in arguments).
LC_MESSAGES
Determine the locale that should be used to
affect the format and contents of diagnostic mes-
sages written to standard error.
NLSPATH
Determine the location of message catalogs for
the processing of LC_MESSAGES .
ASYNCHRONOUS EVENTS
If the sleep utility receives a SIGALRM signal, one of
the following actions shall be taken:
Terminate normally with a zero exit status.
Effectively ignore the signal.
Provide the default behavior for signals described in
the ASYNCHRONOUS EVENTS section of Utility Description
Defaults . This could include terminating with a non-
zero exit status.
The sleep utility shall take the standard action for all
other signals.
STDOUT
Not used.
STDERR
The standard error shall be used only for diagnostic
messages.
OUTPUT FILES
None.
EXTENDED DESCRIPTION
None.
EXIT STATUS
The following exit values shall be returned:
0 The execution was successfully suspended for at
least time seconds, or a SIGALRM signal was
received. See the ASYNCHRONOUS EVENTS section.
>0 An error occurred.
CONSEQUENCES OF ERRORS
Default.
The following sections are informative.
APPLICATION USAGE
None.
EXAMPLES
The sleep utility can be used to execute a command after
a certain amount of time, as in:
(sleep 105; command) &
or to execute a command every so often, as in:
while true
do
command sleep 37
done
RATIONALE
The exit status is allowed to be zero when sleep is
interrupted by the SIGALRM signal because most implemen-
tations of this utility rely on the arrival of that sig-
nal to notify them that the requested finishing time has
been successfully attained. Such implementations thus
do not distinguish this situation from the successful
completion case. Other implementations are allowed to
catch the signal and go back to sleep until the
requested time expires or to provide the normal signal
termination procedures.
As with all other utilities that take integral operands
and do not specify subranges of allowed values, sleep is
required by this volume of IEEE Std 1003.1-2001 to deal
with time requests of up to 2147483647 seconds. This may
mean that some implementations have to make multiple
calls to the delay mechanism of the underlying operating
system if its argument range is less than this.
FUTURE DIRECTIONS
None.
SEE ALSO
wait , the System Interfaces volume of
IEEE Std 1003.1-2001, alarm(), sleep()
COPYRIGHT
Portions of this text are reprinted and reproduced in
electronic form from IEEE Std 1003.1, 2003 Edition,
Standard for Information Technology -- Portable Operat-
ing System Interface (POSIX), The Open Group Base Speci-
fications Issue 6, Copyright (C) 2001-2003 by the Insti-
tute of Electrical and Electronics Engineers, Inc and
The Open Group. In the event of any discrepancy between
this version and the original IEEE and The Open Group
Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be
obtained online at http://www.open-
group.org/unix/online.html .
POSIX 2003 sleep(P)
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