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Linux 2.6 - man page for sleep (linux section 1posix)

SLEEP(P)			    POSIX Programmer's Manual				 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 operand.

OPTIONS
       None.

OPERANDS
       The following operand shall be supported:

       time   A non-negative decimal integer specifying the number of seconds for which  to  sus-
	      pend 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, Inter-
	      nationalization 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  interna-
	      tionalization 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  argu-
	      ments).

       LC_MESSAGES
	      Determine the locale that should be used to affect the format and contents of diag-
	      nostic 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  implementa-
       tions  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	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 orig-
       inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group			       2003					 SLEEP(P)


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