Proper way to concatenate variable strings

Question

I need to create new variable from contents of other variables. Currently I'm using something like this:

- command: echo "{{ var1 }}-{{ var2 }}-{{ var3 }}"   register: newvar 

The problem is:

• Usage of {{ var1 }}...{{ varN }} brings too long strings and very ugly code.
• Usage of {{ newvar.stdout }} a bit better but confusing.
• Usage of set_fact module caches fact between runs. It isn't appropriate for me.

Is there any other solution?

Answer 1

Since strings are lists of characters in Python, we can concatenate strings the same way we concatenate lists (with the + sign):

{{ var1 + '-' + var2 + '-' + var3 }} 

If you want to pipe the resulting string to some filter, make sure you enclose the bits in parentheses:

e.g. To concatenate our 3 vars, and get a sha512 hash:

{{ (var1 + var2 + var3) | hash('sha512') }} 

Note: this works on Ansible 2.3. I haven't tested it on earlier versions.