1send(3) User Contributed Perl Documentation send(3)
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6 Tk::send - Execute a command in a different application
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9 $result = $widget->send(?options,?app=>cmd?arg arg ...?)
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12 This method arranges for cmd (and args) to be 'sent' to the application
13 named by app. It returns the result or an error (hence above should
14 probably be 'wrapped' in eval{} and $@ tested). App may be the name of
15 any application whose main window is on the display containing the
16 sender's main window; it need not be within the same process. If no
17 arg arguments are present, then the string to be sent is contained
18 entirely within the cmd argument. If one or more args are present,
19 they are concatenated separated by white space to form the string to be
20 sent.
21 If the initial arguments of the call begin with ``-'' they are treated
23 as options. The following options are currently defined:
24 -async
26 Requests asynchronous invocation. In this case the send command
27 will complete immediately without waiting for cmd to complete in
28 the target application; no result will be available and errors in
29 the sent command will be ignored. If the target application is in
30 the same process as the sending application then the -async option
31 is ignored.
32 -- Serves no purpose except to terminate the list of options. This
34 option is needed only if app could contain a leading ``-''
35 character.
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38 The name of an application is set initially from the name of the
39 program or script that created the application. You can query and
40 change the name of an application with the appname method.
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43 The send mechanism was designed to allow Tcl/Tk applications to send
44 Tcl Scripts to each other. This does not map very well onto perl/Tk.
45 Perl/Tk "sends" a string to app, what happens as a result of this
46 depends on the receiving application. If the other application is a
47 Tcl/Tk4.* application it will be treated as a Tcl Script. If the
48 "other" application is perl/Tk application (including sends to self)
49 then the string is passed as an argument to a method call of the
50 following form:
51 $mainwindow->Receive(string);
53 There is a default (AutoLoaded) Tk::Receive which returns an error to
55 the sending application. A particular application may define its own
56 Receive method in any class in MainWindow's inheritance tree to do
57 whatever it sees fit. For example it could eval the string, possibly in
58 a Safe "compartment".
59 If a Tcl/Tk application "sends" anything to a perl/Tk application then
61 the perl/Tk application would have to attempt to interpret the incoming
62 string as a Tcl Script. Simple cases are should not be too hard to
63 emulate (split on white space and treat first element as "command" and
64 other elements as arguments).
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67 The send command is potentially a serious security loophole, since any
68 application that can connect to your X server can send scripts to your
69 applications. Hence the default behaviour outlined above. (With the
70 availability of Safe it may make sense to relax default behaviour a
71 little.)
72 Unmonitored eval'ing of these incoming "scripts" can cause perl to read
74 and write files and invoke subprocesses under your name. Host-based
75 access control such as that provided by xhost is particularly insecure,
76 since it allows anyone with an account on particular hosts to connect
77 to your server, and if disabled it allows anyone anywhere to connect to
78 your server. In order to provide at least a small amount of security,
79 core Tk checks the access control being used by the server and rejects
80 incoming sends unless (a) xhost-style access control is enabled (i.e.
81 only certain hosts can establish connections) and (b) the list of
82 enabled hosts is empty. This means that applications cannot connect to
83 your server unless they use some other form of authorization such as
84 that provide by xauth.
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87 "eval" in perlfunc, Safe, system's administrator/corporate security
88 guidelines etc.
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91 application, name, remote execution, security, send
92perl v5.34.0 2021-07-23 send(3)