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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 differ (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 sec-
                 onds 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 vari-
                 ables that are unset or null. (See the Base Definitions  vol-
                 ume  of POSIX.1-2008, Section 8.2, Internationalization Vari-
                 ables 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 ASYNCHRO-
           NOUS  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  sec-
             onds,  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  dis-
       tinguish  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 termi-
       nation 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 Technology
       -- Portable Operating System Interface (POSIX),  The  Open  Group  Base
       Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri-
       cal 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 Standard
       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.ker-
       nel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group                  2013                            SLEEP(1P)