Adding OR editing line only if not present

[Florian Thiel]

Hi!

I'm trying to configure services with cfengine and I don't want to use
DeleteLines/AppendLines constructs because that changes config files
every cfengine run.

What I want to do is the following:
Append a certain line if it's not already there. If it's there, see if
it maches a certain regexp. If it doesn't, replace it.

I'm trying to do it like this:

--snip--
SetLine "allow=10.$(nr).0.0/255.255.0.0 127.0.0.1"
AppendIfNoLineMatching "^allow="

# the part before this adds the line if it's missing; that should work.
# The problem is that LocateLineMatching exits if it doesn't find a
# line.

LocateLineMatching "^allow="
BeginGroupIfNoMatch "^allow=10\.\$(nr)\.0\.0/255\.255\.0\.0 127\.0\.0\.1"
  ReplaceLineWith "allow=10\.$(nr)\.0\.0/255\.255\.0\.0 127\.0\.0\.1"
EndGroup
DefineClasses "restart_webmin"
--snip--

Any suggestions on how to do this more elegantly or at least in a way
that works?

tia,
   Florian
-- 
Florian Thiel - Medienzentrum Kassel
Systembetreuung Internet- und Kommunikationstechnik
Kasseler Schulen am Netz - http://www.medienzentrum-kassel.de