Using the in operator

The in operator tests whether one string contains another string. Here's an example:

if 'spring' in 'springfield'

The preceding expression is true if the spring string is a substring of springfield, which it is. The in operator can also test for membership of arrays as follows:

if $crewmember in ['Frank', 'Dave', 'HAL' ]

When in is used with a hash, it tests whether the string is a key of the hash:

$ifaces = { 'lo'   => '127.0.0.1', 
            'eth0' => '192.168.0.1' }
if 'eth0' in $ifaces {
  notify { "eth0 has address ${ifaces['eth0']}": }
}

How to do it…

The following steps will show you how to use the in operator:

1. Add the following code to your manifest:

   if $::operatingsystem in [ 'Ubuntu', 'Debian' ] {
     notify { 'Debian-type operating system detected': }
   } elseif $::operatingsystem in [ 'RedHat', 'Fedora', 'SuSE', 'CentOS' ] {
     notify { 'RedHat-type operating system detected': }
   } else {
     notify { 'Some other operating system detected': }
   }

2. Run Puppet:

   t@cookbook:~/.puppet/manifests$ puppet apply in.pp
   Notice: Compiled catalog for cookbook.example.com in environment production in 0.03 seconds
   Notice: Debian-type operating system detected
   Notice: /Stage[main]/Main/Notify[Debian-type operating system detected]/message: defined 'message' as 'Debian-type operating system detected'
   Notice: Finished catalog run in 0.02 seconds
   

There's more…

The value of an in expression is Boolean (true or false) so you can assign it to a variable:

$debianlike = $::operatingsystem in [ 'Debian', 'Ubuntu' ]

if $debianlike {
  notify { 'You are in a maze of twisty little packages, all alike': }
}