Variables

Variables in template are given in double curly braces:

hostname {{ name }}

interface Loopback0
 ip address 10.0.0.{{ id }} 255.255.255.255

Variable values are set based on dictionary that is passed to template.

Variable that is passed on in a dictionary may not only be a number or a string, but also for example, a list or a dictionary. Inside template, you can refer to the item by number or key.

Template example templates/variables.txt with usage of different variable variants:

hostname {{ name }}

interface Loopback0
 ip address 10.0.0.{{ id }} 255.255.255.255

vlan {{ vlans[0] }}

router ospf 1
 router-id 10.0.0.{{ id }}
 auto-cost reference-bandwidth 10000
 network {{ ospf.network }} area {{ ospf['area'] }}

And corresponding data_files/vars.yml file with variables:

id: 3
name: R3
vlans:
  - 10
  - 20
  - 30
ospf:
  network: 10.0.1.0 0.0.0.255
  area: 0

Note the use of vlans variable in template: since vlans variable is a list, you can specify which item from list we need

If a dictionary is passed (as in case of ospf variable), you can refer to dictionary objects inside template using one of the variants: ospf.network or ospf['network']

The result will be:

$ python cfg_gen.py templates/variables.txt data_files/vars.yml
hostname R3

interface Loopback0
 ip address 10.0.0.3 255.255.255.255

vlan 10

router ospf 1
 router-id 10.0.0.3
 auto-cost reference-bandwidth 10000
 network 10.0.1.0 0.0.0.255 area 0