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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 dif-
       fer (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 IEEE Std 1003.1-2001, Section 8.2, Internationalization Variables for the prece-
              dence 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 exam-
              ple, 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  writ-
              ten 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 Descrip-
           tion 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 implementa-
       tions 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 operat-
       ing 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, Stan-
       dard  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 .



IEEE/The Open Group                  2003                            SLEEP(1P)