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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 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 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 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  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 original Standard can be  obtained  online
       at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group                  2003                            SLEEP(1P)