Ansible concat default variable and literal string

Question

I'm not able to do a very simple thing.

In my task I'm trying to concat two default variables with a literal string to create a path

- name: "Uploading File"
  copy:
    src: "{{ installer_iso_src_location }}"/"{{ installer_version }}"/filename.iso
    dest: /opt/temp/filename.iso

This gives me a error. Any idea how to concatenate a variable and literal strings?

Solution

Firstly, YAML

1. Your syntax must conform to YAML:

   Strings (scalars) are ordinarily unquoted, but may be enclosed in double-quotes ("), or single-quotes (').

   So you can either write:

   parameter: value
   

   or

   parameter: 'value'
   

   or

   parameter: "value"
   

   The following is not a valid YAML:

   "{{ installer_iso_src_location }}"/"{{ installer_version }}"/filename.iso
   

2. If your value starts with a curly brace { Ansible will try to parse it as a dictionary (YAML is a supserset of JSON, so a dictionary/associative array enclosed in curly braces is a valid syntax).

   Associative arrays are represented using the colon space (: ) in the form key: value, either one per line or enclosed in curly braces ({ }) and separated by comma space (, ).

   If it's not a valid JSON array, Ansible will report a syntax error.

Secondly, Jinja2:

• The majority of parameters in Ansible (the value of when being a notable exception) are Jinja2 templates (strings).

  To refer to an Ansible-variable-value you use a Jinja2 expression delimited by {{ and }} (no quotes involved):

  {{ variable }}
  

  There are two ways to concatenate strings with variable values for your case:

  {{ installer_iso_src_location }}/{{ installer_version }}/filename.iso
  

  or

  {{ installer_iso_src_location + '/' + installer_version + '/filename.iso' }}
  

Now, YAML and Jinja2 combined:

• Since your parameter (string) starts with { character and it is not a valid YAML/JSON dictionary, the YAML parser will fail (see the point 2. of the above YAML requirements).

  In result, for your value to be considered a string by YAML parser, you must enclose the value (Jinja2 template) in quotes:

  src: "{{ installer_iso_src_location }}/{{ installer_version }}/filename.iso"
  

  or

  src: "{{ installer_iso_src_location + '/' + installer_version + '/filename.iso' }}"
  

  or other combination of single and double quotes.

• If your parameter value started with a string other than {, you could use it without quotes, as in the first example in the point 1. above.

---

Lastly, there are two notable exceptions where value is not expected to follow YAML rules:

• Ansible shorthand syntax for modules with key-value pairs joined by =
• free-form parameter, as for example in the command or shell modules