


send(n)                Tk Built-In Commands               send(n)


NAME
       send - Execute a command in a different application

SYNOPSIS
       (send ?options? app cmd ?arg arg ...?)
       (inhibit-send)


DESCRIPTION
       This procedure arranges for cmd (and args) to be executed in the appli-
       cation named by app. It returns the result (converted to a string) that
       procedure 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 procedure to be executed is contained entirely within the cmd argu-
       ment.   If  one or more args are present, they are concatenated to form
       the procedure to be executed, just as for the eval procedure.

       If the initial arguments of the procedure begin  with  ``-''  they  are
       treated as options.  The following options are currently defined:

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

       :displayof widget-name
              Specifies that the target application's main window  is  on  the
              display  of the window given by widget-name, instead of the dis-
              play 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 ``-'' char-
              acter.


APPLICATION NAMES
       The name of an application is set initially from the name of  the  pro-
       gram  or script that created the application.  You can query and change
       the name of an application with the tk appname procedure.


DISABLING SENDS
       The send procedure can be removed from an application  by  calling  the
       inhibit-send  procedure.   If  the  send  procedure is removed then the
       application will not respond to incoming send  requests  anymore,   nor
       will it be able to issue outgoing requests.  Communication can be reen-
       abled by invoking the tk appname procedure.


SECURITY
       The send procedure is potentially a serious  security  loophole,  since



STk                            3.1                              1





send(n)                Tk Built-In Commands               send(n)


       any  application  that can connect to your X server can send scripts to
       your applications.  These incoming scripts can  use  STk  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.


SEE ALSO
       tk








































STk                            3.1                              2


