centos 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
	      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 .

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 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
       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 Technol-
       ogy -- 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 .

IEEE
/The Open Group						       2003								 SLEEP(1P)