1dde(n) Tcl Bundled Packages dde(n)
2______________________________________________________________________________
6
8 dde - Execute a Dynamic Data Exchange command
9
11 package require dde 1.4
12 dde servername ?-force? ?-handler proc? ?--? ?topic?
14 dde execute ?-async? ?-binary? service topic data │
16 dde poke ?-binary? service topic item data
18 dde request ?-binary? service topic item
20 dde services service topic
22 dde eval ?-async? topic cmd ?arg arg ...?
24______________________________________________________________________________
25
28 This command allows an application to send Dynamic Data Exchange (DDE)
29 command when running under Microsoft Windows. Dynamic Data Exchange is
30 a mechanism where applications can exchange raw data. Each DDE transac‐
31 tion needs a service name and a topic. Both the service name and topic
32 are application defined; Tcl uses the service name TclEval, while the
33 topic name is the name of the interpreter given by dde servername.
34 Other applications have their own service names and topics. For in‐
35 stance, Microsoft Excel has the service name Excel.
36
38 The following commands are a subset of the full Dynamic Data Exchange
39 set of commands.
40 dde servername ?-force? ?-handler proc? ?--? ?topic?
42 dde servername registers the interpreter as a DDE server with
43 the service name TclEval and the topic name specified by topic.
44 If no topic is given, dde servername returns the name of the
45 current topic or the empty string if it is not registered as a
46 service. If the given topic name is already in use, then a suf‐
47 fix of the form “ #2” or “ #3” is appended to the name to make
48 it unique. The command's result will be the name actually used.
49 The -force option is used to force registration of precisely the
50 given topic name.
51 The -handler option specifies a Tcl procedure that will be
53 called to process calls to the dde server. If the package has
54 been loaded into a safe interpreter then a -handler procedure
55 must be defined. The procedure is called with all the arguments
56 provided by the remote call.
57 dde execute ?-async? ?-binary? service topic data
59 dde execute takes the data and sends it to the server indicated
60 by service with the topic indicated by topic. Typically, service
61 is the name of an application, and topic is a file to work on.
62 The data field is given to the remote application. Typically,
63 the application treats the data field as a script, and the
64 script is run in the application. The -async option requests
65 asynchronous invocation. The command returns an error message
66 if the script did not run, unless the -async flag was used, in
67 which case the command returns immediately with no error. With‐ │
68 out the -binary option all data will be sent in unicode. For dde │
69 clients which don't implement the CF_UNICODE clipboard format, │
70 this will automatically be translated to the system encoding. │
71 You can use the -binary option in combination with the result of │
72 encoding convertto to send data in any other encoding.
73 dde poke ?-binary? service topic item data
75 dde poke passes the data to the server indicated by service us‐
76 ing the topic and item specified. Typically, service is the
77 name of an application. topic is application specific but can
78 be a command to the server or the name of a file to work on.
79 The item is also application specific and is often not used, but
80 it must always be non-null. The data field is given to the re‐
81 mote application. Without the -binary option all data will be │
82 sent in unicode. For dde clients which don't implement the │
83 CF_UNICODE clipboard format, this will automatically be trans‐ │
84 lated to the system encoding. You can use the -binary option in │
85 combination with the result of encoding convertto to send data │
86 in any other encoding.
87 dde request ?-binary? service topic item
89 dde request is typically used to get the value of something; the
90 value of a cell in Microsoft Excel or the text of a selection in
91 Microsoft Word. service is typically the name of an application,
92 topic is typically the name of the file, and item is applica‐
93 tion-specific. The command returns the value of item as defined
94 in the application. Normally this is interpreted to be a string
95 with terminating null. If -binary is specified, the result is
96 returned as a byte array.
97 dde services service topic
99 dde services returns a list of service-topic pairs that cur‐
100 rently exist on the machine. If service and topic are both empty
101 strings ({}), then all service-topic pairs currently available
102 on the system are returned. If service is empty and topic is
103 not, then all services with the specified topic are returned. If
104 service is non-empty and topic is, all topics for a given ser‐
105 vice are returned. If both are non-empty, if that service-topic
106 pair currently exists, it is returned; otherwise, an empty
107 string is returned.
108 dde eval ?-async? topic cmd ?arg arg ...?
110 dde eval evaluates a command and its arguments using the inter‐
111 preter specified by topic. The DDE service must be the TclEval
112 service. The -async option requests asynchronous invocation.
113 The command returns an error message if the script did not run,
114 unless the -async flag was used, in which case the command re‐
115 turns immediately with no error. This command can be used to
116 replace send on Windows.
117
119 A Tcl interpreter always has a service name of TclEval. Each different
120 interpreter of all running Tcl applications must be given a unique name
121 specified by dde servername. Each interp is available as a DDE topic
122 only if the dde servername command was used to set the name of the
123 topic for each interp. So a dde services TclEval {} command will return
124 a list of service-topic pairs, where each of the currently running in‐
125 terps will be a topic.
126 When Tcl processes a dde execute command, the data for the execute is
128 run as a script in the interp named by the topic of the dde execute
129 command.
130 When Tcl processes a dde request command, it returns the value of the
132 variable given in the dde command in the context of the interp named by
133 the dde topic. Tcl reserves the variable $TCLEVAL$EXECUTE$RESULT for
134 internal use, and dde request commands for that variable will give un‐
135 predictable results.
136 An external application which wishes to run a script in Tcl should have
138 that script store its result in a variable, run the dde execute com‐
139 mand, and then run dde request to get the value of the variable.
140 When using DDE, be careful to ensure that the event queue is flushed
142 using either update or vwait. This happens by default when using wish
143 unless a blocking command is called (such as exec without adding the &
144 to place the process in the background). If for any reason the event
145 queue is not flushed, DDE commands may hang until the event queue is
146 flushed. This can create a deadlock situation.
147
149 This asks Internet Explorer (which must already be running) to go to a
150 particularly important website:
151 package require dde
153 dde execute -async iexplore WWW_OpenURL http://www.tcl-lang.org/
154
156 tk(n), winfo(n), send(n)
157
159 application, dde, name, remote execution
160dde 1.4 dde(n)