Re: Need 'UncommentAndSetValue' or some such

[Adams, Russell L.]

Actually, templates should be on topic here.

However, I was not referring to the configuration files themselves. I
use m4 on my cfengine scripts, because if I repeat a section with
minor changes, it belongs in a macro. Reduces typing, typos, improves
legibility, etc.

Now, that being said, I do take advantage of m4 to fill in some of the
data going into a configuration file at the same time I'm using m4 to
macro a cfengine editfiles section. m4 allows me to perform more
sophisticated text substitution than just $(host). I've got some
examples that use a long magic one-liner inside esyscmd() to create a
chunk of text.

See the EditFiles Examples on cfwiki. I've got each (block edit, full
file replacement edit) setup in a macro, which I've been meaning to
post to cfwiki.

Russell

On Tue, Oct 25, 2005 at 12:15:13PM -0700, Brian C. Hill wrote:
>       I tend to agree. Cannonical edit directives are concise and
> clean (pretty, even?), but they will only take you so far. I mark up
> all of my config files (resolv.conf, ntp.conf, automount configs,
> /etc/system, syslog.conf, etc.) with m4. xml might be a better choice
> in the long run, but m4 has worked well for me across a large number of
> systems with different subnets, domains, roles, timezones, etc..
> 
>       I am using cfe to replace rdist now, making heavy use of
> copy:/shellcommands:. I am considering using some of the cfe mount and
> resolver functionality to replace what I am doing (which will obsolete
> the m4 files for those), but that's just a couple of pieces.
> 
>       Is anyone else using a markup language to 'templatize' their
> config files? This is slightly off-topic - probably better to reply to
> me directly.
> 
> Brian
> ======================================================================
> On Tue, Oct 25, 2005 at 11:03:59AM -0500, Adams, Russell L. wrote:
> > Thats what m4 is for.
> > 
> > Russell
> > 
> > On Tue, Oct 25, 2005 at 10:03:32AM -0400, David Scott Coburn wrote:
> > > 
> > > In many of my cfagent script I have constructs like this:
> > > 
> > > editfiles:
> > > 
> > >         { /etc/postfix/main.cf
> > >             BeginGroupIfNoSuchLine "mydestination = $(host), $(fqhost), 
> > > localhost"
> > >                 DeleteLinesMatching "^mydestination.*"
> > >                 Append "mydestination = $(host), $(fqhost), localhost"
> > >             EndGroup
> > >             BeginGroupIfNoSuchLine "mydomain = $(domain)"
> > >                 DeleteLinesMatching "^mydomain.*"
> > >                 Append "mydomain = $(domain)"
> > >             EndGroup
> > >             DefineClasses "restart_postfix"
> > >         }
> > > 
> > > The bit that bugs me the most about this construct is the repetition
> > > of the text I am searching for and the text to replace it with.
> > > 
> > > What would be nifty would be something like this:
> > > 
> > > editfiles:
> > > 
> > >         { /etc/postfix/main.cf
> > >             UncommentAndSetValue "mydestination ="  "$(host), $(fqhost), 
> > > localhost"
> > >             UncommentAndSetValue "mydomain =" "$(domain)"
> > >             DefineClasses "restart_postfix"
> > >         }
> > > 
> > > The first argument would be the variable that get its value changed,
> > > and the second argument would be what it gets set to.
> > > 
> > > If the value was already set then nothing would happen.  If a variable was
> > > changed then the DefineClass would happen.  If the variable was commented 
> > > out
> > > then it would be uncommented and set to the given value.
> > > 
> > > It seems like this kind of setting of variables in config files to some
> > > value is half of what I use cfengine for and this would be a whole lot
> > > easier to set up and then maintain.
> > > 
> > > Perhaps there is already a better way to do it that I have not found in
> > > the manual yet?
> > > 
> > > Thanks,
> > > 
> > > Scott
> > > 
> > > -- 
> > > * David Scott Coburn
> > > * Brookhaven National Laboratory
> > > * scott@bnl.gov 631.344.7110
> > > * "Assume a spherical cow of uniform density..."
> > > _______________________________________________
> > > Help-cfengine mailing list
> > > Help-cfengine@gnu.org
> > > http://lists.gnu.org/mailman/listinfo/help-cfengine
> > 
> > 
> > _______________________________________________
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> > Help-cfengine@gnu.org
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> 
> -- 
>    _____________________________________________________________________
>   / Brian C. Hill     bchill@bch.net          http://brian.bch.net    \
>   | UNIX Specialist   BCH Technical Services  http://www.bch.net      |
> 
> 
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