Puppet

Currently, it is only possible to turn an augeas resource on or off in its entirety by using the ‘onlyif’ parameter. Often, it is desirable to make different kinds of changes depending on what the augeas tree looks like precisely. For example, if in some file the setting ‘foo’ is not set to ‘1’, check whether the setting exists already; if so, jjust change its value to ‘1’. If not, create the setting and a comment about it; as a rough draft, this would could be written in the following manner:

augeas { fiddle-foo:
  context => "..."
  changes => "
  if match foo size == 0 then
    set foo '1'
    ins #comment before foo
    set #comment[following-sibling::*[1][label() = 'foo']] 'modified by puppet'
  else
    set foo '1'
  end
  "
  onlyif => "get foo != '1'"
}