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send(3tk) Tk Built-In Commands send(3tk) 





NAME


send - Execute a command in a different application






SYNOPSIS


send ?options? app cmd ?arg arg
  ...?








DESCRIPTION


This command arranges for cmd (and args) to be
    executed in the application named by app. It returns the result or
    error from that command execution. App may be the name of any
    application whose main window is on the display containing the sender's main
    window; it need not be within the same process. If no arg arguments
    are present, then the command to be executed is contained entirely within
    the cmd argument. If one or more args are present, they are
    concatenated to form the command to be executed, just as for the eval
    command.


If the initial arguments of the command begin with
    “-” they are treated as options. The following options are
    currently defined:



  

  
Requests asynchronous invocation. In this case the send command
      will complete immediately without waiting for cmd to complete in
      the target application; no result will be available and errors in the sent
      command will be ignored. If the target application is in the same process
      as the sending application then the -async option is ignored.

  

  
Specifies that the target application's main window is on the display of
      the window given by pathName, instead of the display containing the
      application's main window.

  
--

  
Serves no purpose except to terminate the list of options. This option is
      needed only if app could contain a leading “-”
      character.








APPLICATION NAMES


The name of an application is set initially from the name of the
    program or script that created the application. You can query and change the
    name of an application with the tk appname command.






DISABLING SENDS


If the send command is removed from an application (e.g.
    with the command rename send {}) then the application will not
    respond to incoming send requests anymore, nor will it be able to issue
    outgoing requests. Communication can be reenabled by invoking the tk
    appname command.






SECURITY


The send command is potentially a serious security
    loophole. On Unix, any application that can connect to your X server can
    send scripts to your applications. These incoming scripts can use Tcl to
    read and write your files and invoke subprocesses under your name.
    Host-based access control such as that provided by xhost is
    particularly insecure, since it allows anyone with an account on particular
    hosts to connect to your server, and if disabled it allows anyone anywhere
    to connect to your server. In order to provide at least a small amount of
    security, Tk checks the access control being used by the server and rejects
    incoming sends unless (a) xhost-style access control is enabled (i.e.
    only certain hosts can establish connections) and (b) the list of enabled
    hosts is empty. This means that applications cannot connect to your server
    unless they use some other form of authorization such as that provide by
    xauth. Under Windows, send is currently disabled. Most of the
    functionality is provided by the dde command instead.






EXAMPLE


This script fragment can be used to make an application that only
    runs once on a particular display.




if {[tk appname FoobarApp] ne "FoobarApp"} {


    send -async FoobarApp RemoteStart $argv


    exit
}
# The command that will be called remotely, which raises
# the application main window and opens the requested files
proc RemoteStart args {


    raise .


    foreach filename $args {


        OpenFile $filename


    }
}








KEYWORDS


application, dde, name, remote execution, security, send







  

    4.0
    Tk