send(n) Tk (4.0) send(n)
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NAME
send - Execute a command in a different application
SYNOPSIS
send ?options? app cmd ?arg arg ...?
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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:
-async
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.
-displayof pathName
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.
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send(n) Tk (4.0) send(n)
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,
since 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.
KEYWORDS
application, name, remote execution, security, send
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