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OpenDarwin 7.2.1 - man page for dde (opendarwin section n)

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dde(n)				       Tcl Bundled Packages				   dde(n)

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NAME
       dde - Execute a Dynamic Data Exchange command

SYNOPSIS
       package require dde 1.2

       dde servername ?topic?

       dde execute ?-async? service topic ?data?

       dde poke service topic item data

       dde request ?-binary? service topic ?data?

       dde services service topic ?data?

       dde eval ?-async? service topic ?data?
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DESCRIPTION
       This  command  allows an application to send Dynamic Data Exchange (DDE) command when run-
       ning under Microsoft Windows. Dynamic Data Exchange is a mechanism where applications  can
       exchange raw data. Each DDE transaction needs a service name and a topic. Both the service
       name and topic are application defined; Tcl uses the service name TclEval, while the topic
       name is the name of the interpreter given by dde servername. Other applications have their
       own service names and topics. For instance, Microsoft Excel has the service name Excel.

       The eval and execute commands accept the option -async:

       DDE COMMANDS

       The following commands are a subset of the full Dynamic Data Exchange set of commands.

       dde servername ?topic?
	      dde servername registers the interpreter as a DDE  server  with  the  service  name
	      TclEval  and  the topic name specified by topic.	If no topic is given, dde server-
	      name returns the name of the current topic or the empty string if it is not  regis-
	      tered as a service.

       dde execute ?-async? service topic data
	      dde execute takes the data and sends it to the server indicated by service with the
	      topic indicated by topic. Typically, service is the name	of  an	application,  and
	      topic  is  a  file  to work on.  The data field is given to the remote application.
	      Typically, the application treats the data field as a script, and the script is run
	      in  the application.  The -async option requests asynchronous invocation.  The com-
	      mand returns an error message if the script did not run, unless the -async flag was
	      used, in which case the command returns immediately with no error.

       dde poke service topic item data
	      dde  poke  passes  the  data to the server indicated by service using the topic and
	      item specified.  Typically, service is the name of an application.  topic is appli-
	      cation  specific	but  can be a command to the server or the name of a file to work
	      on.  The item is also application specific and is  often	not  used,  but  it  must
	      always be non-null.  The data field is given to the remote application.

       dde request ?-binary? service topic item
	      dde request is typically used to get the value of something; the value of a cell in
	      Microsoft Excel or the text of a selection in Microsoft Word. service is	typically
	      the  name  of  an application, topic is typically the name of the file, and item is
	      application-specific. The command returns the value  of  item  as  defined  in  the
	      application.   Normally  this  is interpreted to be a string with terminating null.
	      If -binary is specified, the result is returned as a byte array.

       dde services service topic
	      dde services returns a list of service-topic pairs  that	currently  exist  on  the
	      machine.	If  service  and topic are both null strings ({}), then all service-topic
	      pairs currently available on the system are returned. If service is null and  topic
	      is  not, then all services with the specified topic are returned. If service is not
	      null and topic is, all topics for a given service are returned.  If  both  are  not
	      null,  if that service-topic pair currently exists, it is returned; otherwise, null
	      is returned.

       dde eval ?-async? topic cmd ?arg arg ...?
	      dde eval evaluates a command and its arguments using the interpreter  specified  by
	      topic.  The  DDE	service  must be the TclEval service.  The -async option requests
	      asynchronous invocation.	The command returns an error message if  the  script  did
	      not run, unless the -async flag was used, in which case the command returns immedi-
	      ately with no error.  This command can be used to replace send on Windows.

DDE AND TCL
       A Tcl interpreter always has a service name of TclEval.	Each different interpreter of all
       running	Tcl  applications  must  be given a unique name specified by dde servername. Each
       interp is available as a DDE topic only if the dde servername command was used to set  the
       name of the topic for each interp. So a dde services TclEval {} command will return a list
       of service-topic pairs, where each of the currently running interps will be a topic.

       When Tcl processes a dde execute command, the data for the execute is run as a  script  in
       the interp named by the topic of the dde execute command.

       When  Tcl  processes  a dde request command, it returns the value of the variable given in
       the dde command in the context of the interp named by the  dde  topic.  Tcl  reserves  the
       variable $TCLEVAL$EXECUTE$RESULT for internal use, and dde request commands for that vari-
       able will give unpredictable results.

       An external application which wishes to run a script in Tcl should have that script  store
       its  result in a variable, run the dde execute command, and the run dde request to get the
       value of the variable.

       When using DDE, be careful to ensure that the event queue is flushed using  either  update
       or  vwait.   This  happens  by default when using wish unless a blocking command is called
       (such as exec without adding the & to place the process in the background).   If  for  any
       reason  the  event  queue  is  not flushed, DDE commands may hang until the event queue is
       flushed.  This can create a deadlock situation.

SEE ALSO
       tk(n), winfo(n), send(n)

KEYWORDS
       application, dde, name, remote execution

dde					       1.2					   dde(n)
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