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RedHat 9 (Linux i386) - man page for dde (redhat section n)

dde(n)				      Tcl Built-In Commands				   dde(n)

_________________________________________________________________________________________________

NAME
       dde - Execute a Dynamic Data Exchange command

SYNOPSIS
       package require dde 1.1

       dde servername ?topic?

       dde ?-async? command service topic ?data?
_________________________________________________________________

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 only option to the dde command is:

       -async Requests asynchronous invocation.  This is valid only for the  execute  subcommand.
	      Normally,  the  dde execute subcommand waits until the command completes, returning
	      appropriate error messages. When the -async option is  used,  the  command  returns
	      immediately, and no error information is available.

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 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 command returns an error if the script did not run. If  the
	      -async flag was used, 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 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.

       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 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.  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

Tcl					       8.1					   dde(n)


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