Yet another dynamic variable problem

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1

I am trying to generate a variable name dynamically, but so far I have been stymied.

I have lists whose names are based upon the OS name:

myos7:

  • os7package1
  • os7package2
  • os7package3

myos8:

  • os8package1
  • os8package2
  • os8package3

I want to access these lists dynamically in a shell command:

  • shell:
    for pkg in “{{‘myos’ + ansible_facts.distribution_major_release}}”; \

do
echo “pkg=$pkg”;
done

All I get in the output from the echo command is ‘myos7’ or ‘myos8’, but not the contents of those variables. If I output the variable in a debug task, I get the expected results, the list of packages:

  • debug:

var: “{{item}}”

with_items:

  • “{{‘myos’ + ansible_facts.distribution_major_release}}”

So what is the difference? Why does it work as expected in the debug task but not in the shell task?

2

I am trying to generate a variable name dynamically, but so far I have
been stymied.

I have lists whose names are based upon the OS name:

> myos7:
> - os7package1
> - os7package2
> - os7package3

> myos8:
> - os8package1
> - os8package2
> - os8package3

I want to access these lists dynamically in a shell command:

> - shell:
> for pkg in "{{'myos' + ansible_facts.distribution_major_release}}"; \
> do \
> echo "pkg=$pkg"; \
> done

You want

lookup('vars', 'myos' ~ ansible_facts.distribution_major_release)

All I get in the output from the echo command is 'myos7' or 'myos8',
but not the contents of those variables. If I output the variable in a
debug task, I get the expected results, the list of packages:

> - debug:
> var: "{{item}}"
> with_items:
> - "{{'myos' + ansible_facts.distribution_major_release}}"

So what is the difference? Why does it work as expected in the debug
task but not in the shell task?

You're doing a double lookup here. Once in with_items and again by using `var` instead of `msg`

V/r,
James Cassell

3

I tried that. I swear I tried that. And it kept telling me that it could not locate my variable. I thought maybe I had mistyped the variable name, but it looked good. It still would not work. But now, of course it does:

TASK [debug] *******************************************************************
ok: [ldappoc4] => (item=myos7) =>
  ansible_loop_var: item
  item: myos7
  myos7:
  - os7package1
  - os7package2
  - os7package3

TASK [shell] *******************************************************************
changed: [ldappoc4] => changed=true
  cmd: for pkg in "[u'os7package1', u'os7package2', u'os7package3']"; do echo "pkg=$pkg"; done
  delta: '0:00:00.031796'
  end: '2019-07-24 04:40:34.798245'
  rc: 0
  start: '2019-07-24 04:40:34.766449'
  stderr: ''
  stderr_lines: <omitted>
  stdout: pkg=[u'os7package1', u'os7package2', u'os7package3']
  stdout_lines: <omitted>

    That is what I expected to see. So at least now I have proof that it will work. I need to go back to my original code and see where I went wrong.
    It has been a long day, sometimes just walking away for a bit makes all the difference in the world.
    Thanks,
    -Mark

4

Okay, I did not describe the problem properly. The code looks more like the following:

vars:
    packages:
      myos7:
          - os7package1
          - os7package2
          - os7package3

      myos8:
          - os8package1
          - os8package2
          - os8package3

  - debug:
        var: "{{item}}"
    with_items:
        - "{{'packages.myos' + ansible_distribution_major_version}}"

  - shell:
        for pkg in "{{lookup('vars', 'packages.myos' ~ ansible_distribution_major_version)}}"; \
        do \
            echo "pkg=$pkg"; \
        done

And the output looks like this:

TASK [debug] *******************************************************************
ok: [ldappoc4] => (item=packages.myos7) =>
  ansible_loop_var: item
  item: packages.myos7
  packages.myos7:
  - os7package1
  - os7package2
  - os7package3

TASK [shell] *******************************************************************
fatal: [ldappoc4]: FAILED! =>
  msg: |-
    The task includes an option with an undefined variable. The error was: No variable found with this name: packages.myos7

My data is actually stored in a dictionary. The debug task is able to interpret that but the lookup plugin is not.
So now what?

5

The debug doesn't work eihter, at least not the way you think.

The debug var: takes a variable name and print out the content of that variable.
As you can see from the above output your item is "item: packages.myos7"

So you
   - debug:
       var: "{{item}}"

actually becomes
   - debug:
       var: "packages.myos7"

and the content of packages.myos7 is the list
   - os7package1
   - os7package2
   - os7package3

What you need is
{{ packages['myos' ~ ansible_distribution_major_version] }}

6

Okay, that makes sense and looks a lot simpler. I will try that.
    Thanks,
    -Mark

7

And that works. The actual 'for' line looks like the following to get one package name per iteration:

        for pkg in $(echo "{{packages['myos' ~ ansible_distribution_major_version]|to_json|regex_replace('[,\[\]]', '')}}");

    But that got me what I am trying to achieve.
    -Mark