How to receive Revision in Azure Pipelines YAML build definition - azure-devops

Question

I created a new build with Azure Pipelines (Azure DevOps) and it worked really well.
Usually, you use $(Rev:.r) to get the revision in the build. Unfortunately, it seems the variable isn't replaced/set in the build steps. The only place where you can use it is the name: property in the YAML document.
Now I set it in the name and extract it in some PowerShell, which isn't necessary if you can get it via an environment variable.
How do I get the Revision (like $(Rev)) in the new builds (outside of the name: property in the YAML document)?
(The Build Agents running on-premise, inside Docker - but this shouldn't affect the things above)

Answer 1

You can't get the revision number without parsing, it is not stored as a separate field somewhere or in an environment variable.
The $(Rev:.r) portion instructs Azure DevOps to come up with the first number that makes the build number unique (and, in that specific example, put a dot in front of it).
Like you said, the only way is to use PowerShell script to get the value:
$buildNumber = $Env:BUILD_BUILDNUMBER
$revision= $buildNumber.Substring($buildNumber.LastIndexOf('.') + 1)
Edit:
You can install the Get Revision Number extension that does it.

Answer 2

Another possible solution to the above problem could be to use counter expression for ex: we difine the variable and use it in a task to build nuget package.
variables:
counterVar: $[counter($(versionVariable),0)]
.......
- task: CmdLine#2
inputs:
script: >
nuget pack ClassLibrary1/ClassLibrary1.csproj
-OutputDirectory $(Build.ArtifactStagingDirectory)
-NonInteractive
-Properties Configuration=release
-Version $(versionVariable).$(counterVar)
-Verbosity Detailed
-IncludeReferencedProjects
Here versionVariable is a custome variable defined in pipelines->variables.And the seed value is 0(2nd param to counter).
It works as below
Let's assume the versionVariable is 1.19
Build Run 1 counterVar will be 0.
Build Run 2 counterVar will be 1.
Now say we change the versionVariable to 1.20
Build Run 3 counterVar will be 0.
https://learn.microsoft.com/en-us/azure/devops/pipelines/process/expressions?view=azure-devops
Check the counter expression in above link it reset its value for diff prefix.
P.S. Benefit of using counter over $(Rev:r) is that it can start from 0 unlike $(Rev:r)