Control Hubs: Bringing It All Together - Smart Home Automation with Linux and Raspberry Pi - page 226

Web Log
Output only.
This is the same as the standard logger but writes its output to a different file, /var/log/minerva/weblog .

Window Alert
Output only.
This displays the message on an X Window terminal using the basic kdialog program. The existing script exports
the DISPLAY variable to display the box on the current system but could be set to any suitably configured installation
of X Window on the network.
If you need this to support Windows users, then you must install some software (such as Apache) onto those
machines to listen for an incoming message and then use it to trigger a small script once the appropriate message is
received. The following code, called message.js , will use the Windows Scripting Host (WSH) to display a suitable box:

message = "";
for (i = 0; i < WScript.Arguments.length; i++) {
message += WScript.Arguments.Item(i) + " ";
}
Wscript.Echo(message);

Note that the file extension is important, as this is used to determine the particular scripting engine.

Administering Conduits
The administration of conduits is simple, as the major work is handled by the commands themselves. The task of
adding conduits to the system is processed by the msgconduit command. This command can either list the existing
conduits, shown earlier, or add a new one, like so:

msgconduit create newconduitname

or add a new command into an existing conduit:

msgconduit add conduitname conduitcommand original command with arguments

N There is also an msginstall command, which is executed automatically during the installation process. Its sole
purpose is to create the existing conduits, listed earlier. You should never need to call this.

Note

Messaging Conduits
Having now gotten some conduits to send and process messages, you need to abstract them one stage further so
they can be controlled from a single script. This is because each conduit has a lot of common functionality, such as
address book lookups, which can be unified into a single place. You therefore create two commands: msgxmit , which
sends messages into the output conduits, and msgrcv , which is called by the various daemons when an input conduit
receives a message.