% @(#)set_back.hlq	13.1.1.1 (ESO-IPG) 06/02/98 18:14:55 
%++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
%.COPYRIGHT  (c)  1990 European Southern Observatory
%.IDENT      set_back.hlq
%.AUTHOR     KB, IPG/ESO
%.KEYWORDS   MIDAS, help files, SET/BACKGROUND
%.PURPOSE    On-line help file for the command: SET/BACKGROUND
%.VERSION    1.0  12-MAR-1990 : Creation, KB
%.VERSION    1.1  22-FEB-1993 : Update, KB
%----------------------------------------------------------------
\se
SECTION./BACKGROUND
\es\co
SET/BACKGROUND					19-JAN-1999  KB
\oc\su
SET/BACKGROUND [method] [echo] [sleep_time]
	put Midas session into "background" mode
\us\pu
Purpose:
        Put Midas session into "background" mode
\up\sy
Syntax:
         SET/BACKGROUND [method] [echo] [sleep_time]
\ys\pa
         method = SOCKETS or FILES, if we want to communicate via Unix
              sockets or via ASCII files.
\\
              For the SOCKETS method the communicating Midas sessions may
              run on the same host or different hosts in the network.
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              If the Midas session from which we will receive commands is not
              running on the same host , the "SOCKETS,remote" has to be used.
\\
              For the FILES method the communicating Midas sessions have
              to run on the same host.
\ap\pa
         echo = ON or OFF, to echo the no. of bytes received and the unit
              of the sending Midas or not;
\\
              defaulted to ON
\ap\pa
         sleep_time = no. of seconds to wait before looking for input;
\\
              only applicable for `method'=FILES, defaulted to 1
\ap\sa
See also:
         CLEAR/BACKGROUND, CONNECT/BACK_MIDAS
\as\no
Note:  
         This command currently works only in Unix, not in VMS!
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         In background mode Midas does not accept input typed at the keyboard.
         Instead Midas waits for commands sent by other Midas sessions
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         If communicating Midas sessions run on the same host, they must be
         started in parallel mode.
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         If the communication is based on files, the background Midas receives
         a signal from the sending Midas when a command has been sent.
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         The par. `sleep_time' is only needed for those cases where the
         sender is not another Midas session but a stand-alone program 
         on a different host executing in a different environment, e.g.
         OS/9 or "Rocky Mountain Basic" from HP.
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         If the communication is based on sockets, i.e. the Unix OSX interfaces
         are used, the SET/BACKGROUND command has to be given before any other
         Midas connects to this session via the CONNECT/BACK_MIDAS command 
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         The echo can be updated later on by another call to SET/BACK,
         however, the method remains fixed.
\on\exs
Examples:
\ex
         SET/BACKGR 
          Put current Midas into background mode, use ASCII files for 
          communication and echo the sender Midas unit for incoming commands.
\xe \ex
         SET/BACKGR sockets off
          Put current Midas into background mode, use the osx interfaces 
          communication and do not echo the sender Midas unit for incoming
          commands.
\\
          Only input from Midas sessions running on the same host is received.
\xe \ex
         SET/BACKGR sockets,remote off
          As above, but input from Midas sessions running on other hosts in
          the network is received.
\xe \sxe