sleep(P)                                               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 op-
       erand.

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 internationaliza-
              tion  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 internationalization  variables
              used  to  determine  the  values  of locale cate-
              gories.)

       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 mes-
              sages 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:

       Terminate normally with a zero exit status.

       Effectively ignore the signal.

       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 implemen-
       tations of this utility rely on the arrival of that sig-
       nal 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 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 Operat-
       ing System Interface (POSIX), The Open Group Base Speci-
       fications Issue 6, Copyright (C) 2001-2003 by the Insti-
       tute 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 .



POSIX                         2003                     sleep(P)
