Check if arrays are defined and not empty in ansible

Question

I have the following code

- set_fact:
    MY_HOSTNAME: "SOME VALUE"
    MY_SERVER: "00.00.00.00"
- name: Get MY server
  set_fact:
    MY_SERVER: "{{ groups[MY_HOSTNAME][0] }}"
  when: groups[MY_HOSTNAME] is defined

In the above code, groups[MY_HOSTNAME] is an array. What is the best way to check that groups[MY_HOSTNAME] is defined and also that it is not empty If it is either of that I want the value 00.00.00.00 to be assigned to MY_SERVER

Phil M · Answer 1 · 2017-12-12T15:14:13.897

53

I don't know if it's version specific, but I'm currently running ansible-2.3.2 on RHEL6 and I had to put quotes around the group name to get it to work for me:

when: groups["GROUP_NAME"] is defined and (groups["GROUP_NAME"]|length>0)

Edit: I couldn't add this as a comment to techraf's answer because I don't have enough reputation.

edited Dec 12 '17 at 15:14

answered Dec 12 '17 at 15:05

Phil M

751
4
6

Thank you... but I'm still frustrated that len(foo) (the Python way of checking length) doesn't work. – pedz Apr 12 '19 at 18:44
5

Be careful with this: `| length` works on a string as well. If the input is a string and not an array it will simply return the length of the string – EM0 Aug 28 '19 at 11:13

techraf · Answer 2 · 2017-12-08T07:53:15.913

32

list | length filter returns the number of elements. If it is zero, the list is empty.

For a conditional value use if or ternary filter (example in this answer).

For a composite conditional (groups[MY_HOSTNAME]| default([])) | length.

edited Dec 08 '17 at 07:53

answered Dec 08 '17 at 07:29

techraf

64,883
27
193
198

1

Is there a way to check if it is undefined and not empty at the same time? – kosta Dec 08 '17 at 07:37
What have you tried? What problem did you encounter? – techraf Dec 08 '17 at 07:39
2

I tried `groups[MY_HOSTNAME] is defined and groups[MY_HOSTNAME] | length > 0`, but it does not seem to work – kosta Dec 08 '17 at 07:45

stackprotector · Answer 3 · 2023-06-23T13:36:28.240

You can first check if it is indeed a list and then check if it has more than one element:

when:
  - groups['MY_GROUP_NAME'] is defined
  - groups['MY_GROUP_NAME'] is not string
  - groups['MY_GROUP_NAME'] is not mapping
  - groups['MY_GROUP_NAME'] is iterable
  - groups['MY_GROUP_NAME'] | length > 0

You can also use type_debug, but it is discouraged by the official docs:

when:
  - groups['MY_GROUP_NAME'] is defined
  - groups['MY_GROUP_NAME'] | type_debug == 'list'
  - groups['MY_GROUP_NAME'] | length > 0

Use 'MY_GROUP_NAME', if you directly provide the name of the group as a string or use MY_GROUP_NAME (without quotes), if it is a variable.

Michal Zmuda · Answer 4 · 2022-10-14T08:54:57.937

0

try this one (it checks if variable is defined and if it is a iterable like list)

when: (groups["GROUP_NAME"] is defined) and (groups["GROUP_NAME"] is iterable)

edited Oct 14 '22 at 08:54

answered Oct 10 '22 at 18:49

Michal Zmuda

5,381
3
43
39

Your answer could be improved by adding more information on what the code does and how it helps the OP. – Tyler2P Oct 12 '22 at 20:02

Check if arrays are defined and not empty in ansible

4 Answers4

Linked