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 (con-
       sult 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 precedence  of  international-
              ization 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 stan-
              dard 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 imple-
       mentations 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, Copy-
       right (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.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                                     SLEEP(1P)