RE: [Cfengine-develop] Re: Homework

[Andrews, Martin]

Cool. My first impression is that something like "with" and "over" namespace
manipulation would be perfect to resolve some of my yearnings. I have been
wanting to reuse an imported config file with different class and macro
settings within the same run. For example if I have a cfengine file that
would manage an /etc/init.d service (copies the script, manages the rc
links, makes sure the service is running). I would like to reimport that
file once for each service. I imagine something like this"

import:
  with {
        service="cfexecd"
        src_script=$(golddir)/cfexecd.init
        run_in_rc2=any
        reload=updated_config_files
        startnum=70
        killnum=30
        }
    sysvinit.cf

Note that I mix macro definitions and group/class definitions. Maybe the
difference between the two should be better indicated, but I would like
classes to be namespaced as well.

Not sure where you are going with multiple interpolation - how would you use
that. The current method to avoid single interpolation by escaping the
refence as "echo $(DOLLAR)(myvar)" has worked for me so far.

Martin

> -----Original Message-----
> From: Andrew Stribblehill [mailto:address@hidden
> Sent: Wednesday, March 05, 2003 5:24 AM
> To: address@hidden
> Subject: Re: [Cfengine-develop] Re: Homework
> 
...
> Zope has a <dtml-over> tag for iteration over a list, and <dtml-with>
> to put an associative array into the current namespace. It is used
> thus:
> 
> <dtml-over "mySimpleList">
>   <a href="&dtml-item;">This item</a>
> </dtml-over>
> 
> <dtml-over "myListOfDicts">
>   <dtml-with "item">
>     <a href="&dtml-webpage;">&dtml-description;</a>
>   </dtml-with>
> </dtml-over>
> 
> 
> By analogy, Cfengine could have something like this:
> 
> control:
>   rootCrontabs = [ { minute="05" command="gratuitousMonitor" },
>                    { minute="10" command="pkill gratuitousMonitor" } ]
> 
> editfiles:
>   linux::
>     over rootCrontabs
>       with item
>         { /etc/cron.d/local
>           AppendIfNoSuchLine "$(minute) * * * * root $(command)"
>       }
> 
> Thinking about implementation details just for a moment, the 'over'
> and 'with' keywords would overlay a namespace onto the base one so
> you'd have:
> 
> namespace of 'item'
> namespace of rootCrontabs which contains 'item' and maybe 'itemNumber'
> base namespace (contains, for ecample, sysadm)
> 
> in order of visibility. This is also pleasant because if, for
> example, you didn't want to define some properties for some
> associative arrays, you could just use the default one lower down the
> namespace stack:
> 
> 
> control:
>   minute = "10"
>   hour = "*"
>   day = "*"
>   month = "*"
>   dow = "*"
>   user = "root"
>   rootCrontabs = [ { command="hello" },
>                    { minute="13" command="goodbye"}
> 
> editfiles:
>   linux::
>     over rootCrontabs with item
>       { /etc/cron.d/local
>       AppendIfNoSuchLine "$(minute) $(hour) $(day) $(month) ". \
>         "$(dow) $(user) $(command)"
>       }
> 
> Something else we need to look at is string interpolation. How to
> stop it happening, how to cause it to be interpolated multiple times?
> 
> Perl has '' to mean don't interpolate; Python allows either '' or ""
> and doesn't interpolate unless you give it an associative array to
> work on, i.e.
>   "Charlie had %(num) pigeon%(plural)" % {num="1", plural=""}
>