Set bash command output into an azure yml variable - azure-devops

Question

I'm working with Azure DevOps and I need to set the return of bash commands into some variables, for example I have the following:
variables:
VERSION: 7.2 # works fine
FILE_VERSION: ${{cat public/VERSION}} # syntax error
I tried some some variations from ${{}} without success and I could not found the right syntax for it, but I think it must be possible.

Answer 1

You should use a bash step for that.
Like this:
steps:
- bash: |
echo "##vso[task.setvariable variable=FILE_VERSION]$(cat public/VERSION)"

Answer 2

You need to do this in two steps
STEP 1: Set static value first
variables:
VERSION: 7.2
STEP 2: Create step to calculate the value
Note this will only be available for subsequent steps
- bash: |
FILE_VERSION="$(cat public/VERSION)"
echo "##vso[task.setvariable variable=FILE_VERSION]$FILE_VERSION"
Resources:
https://learn.microsoft.com/en-us/azure/devops/pipelines/process/variables?view=azure-devops&tabs=yaml%2Cbatch

Answer 3

We shouldn't use cat command when defining variables. The command should be located in tasks/steps.
According to your description, I assume you're trying to pass the content of public/7.2 to FILE_VERSION variable. Here's my test:
1.Azure Devops Git repo:
2.Define the VERSION variable:
variables:
VERSION: 7.2
Run the cat command and set job-scoped variable:
- bash: |
FILE_VERSION=$(cat public/$(VERSION))
echo "##vso[task.setvariable variable=FILE_VERSION]$FILE_VERSION"
The whole yaml:
trigger:
- master
pool:
vmImage: 'ubuntu-latest'
variables:
VERSION: 7.2
steps:
- bash: |
FILE_VERSION=$(cat public/$(VERSION))
echo "##vso[task.setvariable variable=FILE_VERSION]$FILE_VERSION"
#Use second bash task to test the variable.
- task: Bash#3
inputs:
targetType: 'inline'
script: |
echo $(FILE_VERSION)