If the regular mechanisms for setting classes do not produce the results
you require for your configuration, you can write your own routines to
concoct the classes of your dreams. Plugin modules are added to cfagent
programs from within the actionsequence, (see Reference manual). They
allow you to write special code for answering questions which are too
complex to answer using the other mechanisms above. This allows you to
control classes which will be switched on and the moment at which your
module attempts to evaluate the condition of the system.
Modules must lie in a special directory defined by the variable
moduledirectory.
They must have a name of the form `module:mymodule' and they
must follow a simple protocol. Cfagent will only execute a module which
is owned either by root or the user who is running cfagent, if it lies
in the special directory and has the special name. A plug-in module may
be written in any language, it can return any output you like, but lines
which begin with a `+' sign are treated as classes to be defined
(like `-D'), while lines which begin with a `-' sign are
treated as classes to be undefined (like `-N'). Lines starting
with `=' are variables/macros to be defined. Any other lines of
output are cited by cfagent, so you should normally make your module
completely silent. Here is an example module written in perl. First we
define the module in the cfagent program:
Note that the class definitions for the module can also be defined in as
AddInstallables, if this is more convenient. NOTE: you must
declare the classes before using them in the cfagent configuration, or else
those actions will be ignored.
Next we write the plugin itself.
#!/usr/bin/perl
#
# module:myplugin
#
# lots of computation....
if (special-condition)
{
print "+specialclass";
}
Modules inherit the environment variables from cfagent and accept arguments, just
as a regular shellcommand does.
#!/bin/sh
#
# module:myplugin
#
/bin/echo $*
Cfagent defines the classes as an environment variable so that programs
have access to these. E.g. try the following module:
#!/usr/bin/perl
print "Decoding $ENV{CFALLCLASSES}\n";
@allclasses = split (":","$ENV{CFALLCLASSES}");
while ($c=shift(@allclasses))
{
$classes{$c} = 1;
print "$c is set\n";
}
Modules can define macros in cfagent by outputting strings of the form
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