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 .