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 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 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 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  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 .