sleep(1p) — Linux manual page
SLEEP(1P) POSIX Programmer's Manual SLEEP(1P)
PROLOG
This manual page is part of the POSIX Programmer's Manual. The
Linux implementation of this interface may differ (consult the
corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
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 operand.
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 internationalization
variables that are unset or null. (See the Base
Definitions volume of POSIX.1‐2017, Section 8.2,
Internationalization Variables for the precedence of
internationalization variables used to determine the
values of locale categories.)
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 messages 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:
1. Terminate normally with a zero exit status.
2. Effectively ignore the signal.
3. Provide the default behavior for signals described in the
ASYNCHRONOUS EVENTS section of Section 1.4, 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 implementations of this
utility rely on the arrival of that signal 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 POSIX.1‐2017 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(1p)
The Base Definitions volume of POSIX.1‐2017, Chapter 8,
Environment Variables
The System Interfaces volume of POSIX.1‐2017, alarm(3p),
sleep(3p)
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic
form from IEEE Std 1003.1-2017, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The
Open Group Base Specifications Issue 7, 2018 Edition, Copyright
(C) 2018 by the Institute 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.opengroup.org/unix/online.html .
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