[SOLVED] Bash Indirect expansion doesn't seem to work in cloud build bash scripts?

Bash Indirect expansion doesn't seem to work in cloud build bash scripts?

Bash has indirect expansion with the following format:

echo ${!VARIABLE}

However it doesn't seem to work in a google cloud build step using the bash entrypoint. I have set the values of _BAR and _FOO_BAR under substitutions: and I also have automapSubstitutions: true so the substitutions are being set as environment variables in bash. I'm trying to follow this answer as an example. I have the following step:

- id: Test Indirect Expansion
  name: "gcr.io/cloud-builders/gsutil"
  entrypoint: 'bash'
  args:
    - -c
    - |
      #!/usr/bin/env bash
      echo "Value of substitution _BAR: ${_BAR}"
      echo "Value of substitution _FOO_BAR: ${_FOO_BAR}"
      export foobar=_FOO${_BAR}
      echo "expansion: ${foobar}"
      echo "indirect expansion: ${!foobar}"

However the output for the step shows indirect expansion as blank:

Value of substitution _BAR: _BAR
Value of substitution _FOO_BAR: google cloud
expansion: _FOO_BAR
indirect expansion:

These commands work on my local bash terminal but not here. I cant find anything mentioning indirect substitution for cloud build. But I don't see any reason why it wouldn't support it. Can anyone shed some light on this?

Solution

Since this seems to be a rare issue, I figured that bash scripts inside of Cloud build steps don't support this kind of indirect expansion.

I was hoping to dynamically set variable names using this. Instead I just used if statements inside the bash script to do what I needed to do, in case anyone finds this in the future.