posix man page for sleep

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 correspond-
       ing 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.1-2008,	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.1-2008 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 Base Definitions volume of POSIX.1-2008, Chapter 8, Environment Variables

       The System Interfaces volume of POSIX.1-2008, alarm(), sleep()

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2013 Edition, Standard for Information Technol-
       ogy  --	Portable  Operating  System  Interface (POSIX), The Open Group Base Specifications Issue 7, Copyright (C) 2013 by the Institute of
       Electrical and Electronics Engineers, Inc and The Open Group.  (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) 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 Stan-
       dard is the referee document. The original Standard can be obtained online at http://www.unix.org/online.html .

       Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source
       files to man page format. To report such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE
/The Open Group						       2013								 SLEEP(1P)