Originální popis anglicky:
sleep - suspend execution for an interval
Návod, kniha: POSIX Programmer's Manual
sleep time
The
sleep utility shall suspend execution for at least the integral
number of seconds specified by the
time operand.
None.
The following operand shall be supported:
- time
- A non-negative decimal integer specifying the number of
seconds for which to suspend execution.
Not used.
None.
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
IEEE Std 1003.1-2001, 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 .
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 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.
Not used.
The standard error shall be used only for diagnostic messages.
None.
None.
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.
Default.
The following sections are informative.
None.
The
sleep utility can be used to execute a command after a certain amount
of time, as in:
or to execute a command every so often, as in:
while true
do
command sleep 37
done
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
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.
None.
wait , the System Interfaces volume of
IEEE Std 1003.1-2001,
alarm(),
sleep()
Portions of this text are reprinted and reproduced in electronic form from IEEE
Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable
Operating System Interface (POSIX), The Open Group Base Specifications Issue
6, Copyright (C) 2001-2003 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
.
