On Thu, Jun 23, 2011 at 5:41 PM, Daniel V. Klein <d...@lonewolf.com> wrote:
>
> ifvarclass() says "if the named class exists, do something"
>
> fileexists() says "if the named file exists, make the class expression
> 'true'" and that is used to create a named class.
>
> The two are incompatible (because the latter is only used in class promises).
> Your example isn't clear, as it appears to use the target as both a
> directory and a file. What you probably want to do is use a transformer
> attribute. But maybe not :-)
>
> -Dan
Dear Dan,
Thank you for your reply. My case is (I hope this is a clear
example): I want my system to have a certain PHP package (let's say
"Fileinfo"). I want Cfengine to install this package for me only if
it does not already exist. (I can tell if it is installed by checking
for /usr/lib64/php/modules/fileinfo.so or by checking the exit status
of "pear list fileinfo".)
I already check if /usr/lib64/php/modules/fileinfo.so exists, and if
it does, I add "extension=fileinfo.so" to /etc/php.ini and reload the
httpd.
I just don't like not being able to use the result of that check
directly to control installation of the package. (I have to set an
inverse class.)
I tried using the transformer attribute as you kindly suggested, but
it runs the command whether the file exists or not:
{{{
bundle agent example {
files:
"/usr/lib64/php/modules/fileinfo.so"
create => "true",
transformer => "/usr/bin/pecl install fileinfo";
}
}}}
Mark describes Cfengine 3 as a low-level, flexible and powerful
language. Adding an "ifnotvarclass" promise attribute (adding the
ability to AND NOT dynamically interpolated variable classes with
static classes) would increase the flexibility and power of the
Cfengine language.
Just thinking out loud, if we had an "iffunc" attribute, we could
use that to AND it with the statically set classes; and ifnotfunc,
would AND NOT it with the static classes, for example:
commands:
"/usr/bin/pecl install fileinfo"
ifnotfunc => fileexists("/usr/lib64/php/modules/fileinfo.so");
That would only run the command if the fileexists function returns
false. Very concise and powerful expression of the sysadmin's
intention, all in a single promise.
Sincerely,
Aleksey
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