Azure Pipelines overwrite pipeline variable - azure-devops

Question

How does one overwrite a pipeline variable or how does one create a pipeline variable from a job?
I'm running a prepare job where I extract the current git tag into a variable that I need in following jobs so I decided to create a pipeline variable and overwrite its value in the first job:
variables:
GIT_TAG: v0.0.1
jobs:
- job: job1
pool:
vmImage: 'ubuntu-16.04'
steps:
- powershell: |
Write-Host "##vso[task.setvariable variable=GIT_TAG]$(git describe --tags --always)"
But, in the next job GIT_TAG has the initial value of v0.0.1.

Answer 1

By default, if you overwrite a variable the value is available only to his job, not to the sequence jobs.
Passing variables between jobs in the same stage is a bit more complex, as it requires working with output variables.
Similarly to the example above, to pass the FOO variable:
Make sure you give a name to the job, for example job: firstjob
Likewise, make sure you give a name to the step as well, for example: name: mystep
Set the variable with the same command as before, but adding ;isOutput=true, like: echo "##vso[task.setvariable variable=FOO;isOutput=true]some value"
In the second job, define a variable at the job level, giving it the value $[ dependencies.firstjob.outputs['mystep.FOO'] ] (remember to use single quotes for expressions)
A full example:
jobs:
- job: firstjob
pool:
vmImage: 'Ubuntu-16.04'
steps:
# Sets FOO to "some value", then mark it as output variable
- bash: |
FOO="some value"
echo "##vso[task.setvariable variable=FOO;isOutput=true]$FOO"
name: mystep
# Show output variable in the same job
- bash: |
echo "$(mystep.FOO)"
- job: secondjob
# Need to explicitly mark the dependency
dependsOn: firstjob
variables:
# Define the variable FOO from the previous job
# Note the use of single quotes!
FOO: $[ dependencies.firstjob.outputs['mystep.FOO'] ]
pool:
vmImage: 'Ubuntu-16.04'
steps:
# The variable is now available for expansion within the job
- bash: |
echo "$(FOO)"
# To send the variable to the script as environmental variable, it needs to be set in the env dictionary
- bash: |
echo "$FOO"
env:
FOO: $(FOO)
More info you can find here.