Puppet defines to build a complex file across all nodes. Useful for creating config files containing IP addresses of nodes in distributed systems.

buildfile.pp

# Export a single line 
#
# == Parameters
#
# [*namevar*]
#   Line of text to include in the file to build
#
# [*file*]
#   The file the supplied line will be included in
#
# == Examples
#   exportline { "$name $ipaddress":
#     file => "/etc/app/clients"
#   }
#
define exportline($file) {
  $tag = regsubst($file, "/", "-", "G")
  @@exec { "check $name":
    command => "/bin/true",
    unless => "grep '$name' $file",
    tag => "export$tag",
    notify => Exec["clear $file"]
  }
  @@exec { "set $name":
    command => "echo '$name' >> $file",
    refreshonly => true,
    subscribe => Exec["clear $file"],
    tag => "export$tag"
  }
}

# Collect all exported lines of data and build the
# desired file.
#
# The resulting file can be referenced with the
# File["/path/to/file"} resource to meet order 
# requirement needs
#
# == Parameters
#
# [*namevar*]
#   File to build and put all lines into
#
# == Examples
#   collectfile { "/etc/app/clients": }
#
#   exec { "test":
#     require => File{"/etc/app/clients"]
#   }
#
define collectfile($trigger=false) {
  $tag = regsubst($name, "/", "-", "G")

  file {$name:
    ensure => file
  }
  exec { "clear $name":
    command => "echo '' |> $name",
    refreshonly => true
  }

  Exec<<| tag=="export$tag" |>> {
    before => File["$name"]
  }

  if $trigger {
    File["$name"] {
      notify => $trigger,
      before => $trigger
    }
  }
}