'\" '\" Copyright (c) 1997 Sun Microsystems, Inc. '\" Copyright (c) 2001 ActiveState Corporation. '\" '\" See the file "license.terms" for information on usage and redistribution '\" of this file, and for a DISCLAIMER OF ALL WARRANTIES. '\" '\" RCS: @(#) $Id: dde.n,v 1.1.1.1 2007/07/10 15:04:23 duncan Exp $ '\" .so man.macros .TH dde n 1.2 dde "Tcl Bundled Packages" .BS '\" Note: do not modify the .SH NAME line immediately below! .SH NAME dde \- Execute a Dynamic Data Exchange command .SH SYNOPSIS .sp \fBpackage require dde 1.2\fR .sp \fBdde eval\fR ?\fB\-async\fR? \fIservice cmd\fR ?\fIarg ...\fR? .sp \fBdde execute\fR ?\fB\-async\fR? \fIservice topic data\fR .sp \fBdde poke \fIservice topic item data\fR .sp \fBdde request\fR ?\fB\-binary\fR? \fIservice topic data\fR .sp \fBdde servername\fR ?\fItopic\fR? .sp \fBdde services \fIservice topic\fR .BE .SH DESCRIPTION .PP This command allows an application to send Dynamic Data Exchange (DDE) command when running under Microsoft Windows. Dynamic Data Exchange is a mechanism where applications can exchange raw data. Each DDE transaction needs a \fIservice name\fR and a \fItopic\fR. Both the \fIservice name\fR and \fItopic\fR are application defined; Tcl uses the service name \fBTclEval\fR, while the topic name is the name of the interpreter given by \fBdde servername\fR. Other applications have their own \fIservice name\fRs and \fItopic\fRs. For instance, Microsoft Excel has the service name \fBExcel\fR. .PP The \fBeval\fR and \fBexecute\fR commands accept the option \fB\-async\fR: .SH "DDE COMMANDS" .PP The following commands are a subset of the full Dynamic Data Exchange set of commands. .TP \fBdde servername \fR?\fItopic\fR? \fBdde servername\fR registers the interpreter as a DDE server with the service name \fBTclEval\fR and the topic name specified by \fItopic\fR. If no \fItopic\fR is given, \fBdde servername\fR returns the name of the current topic or the empty string if it is not registered as a service. .TP \fBdde execute\fR ?\fB\-async\fR? \fIservice topic data\fR \fBdde execute\fR takes the \fIdata\fR and sends it to the server indicated by \fIservice\fR with the topic indicated by \fItopic\fR. Typically, \fIservice\fR is the name of an application, and \fItopic\fR is a file to work on. The \fIdata\fR field is given to the remote application. Typically, the application treats the \fIdata\fR field as a script, and the script is run in the application. The \fB\-async\fR option requests asynchronous invocation. The command returns an error message if the script did not run, unless the \fB\-async\fR flag was used, in which case the command returns immediately with no error. .TP \fBdde poke \fIservice topic item data\fR \fBdde poke\fR passes the \fIdata\fR to the server indicated by \fIservice\fR using the \fItopic\fR and \fIitem\fR specified. Typically, \fIservice\fR is the name of an application. \fItopic\fR is application specific but can be a command to the server or the name of a file to work on. The \fIitem\fR is also application specific and is often not used, but it must always be non-null. The \fIdata\fR field is given to the remote application. .TP \fBdde request\fR ?\fB\-binary\fR? \fIservice topic item\fR \fBdde request\fR 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. \fIservice\fR is typically the name of an application, \fItopic\fR is typically the name of the file, and \fIitem\fR is application-specific. The command returns the value of \fIitem\fR as defined in the application. Normally this is interpreted to be a string with terminating null. If \fB\-binary\fR is specified, the result is returned as a byte array. .TP \fBdde services \fIservice topic\fR \fBdde services\fR returns a list of service-topic pairs that currently exist on the machine. If \fIservice\fR and \fItopic\fR are both null strings ({}), then all service-topic pairs currently available on the system are returned. If \fIservice\fR is null and \fItopic\fR is not, then all services with the specified topic are returned. If \fIservice\fR is not null and \fItopic\fR 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. .TP \fBdde eval\fR ?\fB\-async\fR? \fItopic cmd \fR?\fIarg arg ...\fR? \fBdde eval\fR evaluates a command and its arguments using the interpreter specified by \fItopic\fR. The DDE service must be the \fBTclEval\fR service. The \fB\-async\fR option requests asynchronous invocation. The command returns an error message if the script did not run, unless the \fB\-async\fR flag was used, in which case the command returns immediately with no error. This command can be used to replace \fBsend\fR on Windows. .SH "DDE AND TCL" A Tcl interpreter always has a service name of \fBTclEval\fR. Each different interpreter of all running Tcl applications must be given a unique name specified by \fBdde servername\fR. Each interp is available as a DDE topic only if the \fBdde servername\fR command was used to set the name of the topic for each interp. So a \fBdde services TclEval {}\fR command will return a list of service-topic pairs, where each of the currently running interps will be a topic. .PP When Tcl processes a \fBdde execute\fR command, the data for the execute is run as a script in the interp named by the topic of the \fBdde execute\fR command. .PP When Tcl processes a \fBdde request\fR 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 \fB$TCLEVAL$EXECUTE$RESULT\fR for internal use, and \fBdde request\fR commands for that variable will give unpredictable results. .PP An external application which wishes to run a script in Tcl should have that script store its result in a variable, run the \fBdde execute\fR command, and the run \fBdde request\fR to get the value of the variable. .PP When using DDE, be careful to ensure that the event queue is flushed using either \fBupdate\fR or \fBvwait\fR. This happens by default when using \fBwish\fR unless a blocking command is called (such as \fBexec\fR without adding the \fB&\fR 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. .SH EXAMPLE This asks Internet Explorer (which must already be running) to go to a particularly important website: .CS package require dde \fBdde execute\fR iexplore WWW_OpenURL http://www.tcl.tk/ .CE .SH "SEE ALSO" tk(n), winfo(n), send(n) .SH KEYWORDS application, dde, name, remote execution