Can I substring a variable in Azure Pipelines?

My other approach would be to use a bash task and overwrite the variable there but finding something build-in that can do this would be way better solution.

I agree with Lucas. There is no such built-in task to get the first 7 characters of $(Build.SourceVersion) in Azure DevOps.

We could use the command line/powershell task to split long sha into short sha:

echo $(Build.SourceVersion)

set TestVar=$(Build.SourceVersion)

set MyCustomVar=%TestVar:~0,7%

echo %MyCustomVar%

echo ##vso[task.setvariable variable=ShortSourceVersion]%MyCustomVar%

In this case, we could get the short versions of Build.SourceVersion and set it as environment variable.

Then we could set this command line task as a task group:

So, we could use this task to set the ShortSourceVersion directly.

Hope this helps.

You are right, there is no native way to do it. You will have to write a script to transform the variable.

Here is an example:

trigger:
- master

resources:
- repo: self

stages:
- stage: Build
  displayName: Build image
  jobs:  
  - job: Build
    displayName: Build
    pool:
      vmImage: 'ubuntu-latest'
    steps:
    - task: CmdLine@2
      inputs:
        script: ' x=`echo "$(Build.SourceVersion)" | head -c 7`; echo "##vso[task.setvariable variable=MyVar]$x"'
    - task: CmdLine@2
      inputs:
        script: 'echo "$(MyVar)"'

Here is the shortest version that I use for this job;

- bash: |
    longcommithash=$(Build.SourceVersion)
    echo "##vso[task.setvariable variable=shorthash;]$(echo ${longcommithash::9})"

It gives you the output as shown below;

On Azure devops it's possible to be done using batch technique indeed - like other answers propose in here - however I wanted to remove string from the end of string - and with batch this gets more complex ( See following link ).

Then I've concluded to use Azure's built-in expressions, for example like this:

- name: sourceBranchName
  value: ${{ replace(variables['Build.SourceBranch'], 'refs/heads/') }}

replace will have similar effect to substring - so it will remove unnecessary part from original string.

If however you want to concatenate some string and then remove it from original name - it's possible to be done using for instance format function:

- name: originBranchName
  value: ${{ replace(variables.sourceBranchName, format('-to-{0}', variables.dynamicvar ) ) }}

If dynamicvar is a - then function will remove -to-a from branch name.

Sure you can! If you absolutely must. Here is a runtime computation taking the first 7 characters of the Build.SourceVersion variable.

variables:
  example: ${{ format('{0}{1}{2}{3}{4}{5}{6}', variables['Build.SourceVersion'][0], variables['Build.SourceVersion'][1], variables['Build.SourceVersion'][2], variables['Build.SourceVersion'][3], variables['Build.SourceVersion'][4], variables['Build.SourceVersion'][5], variables['Build.SourceVersion'][6]) }}

NB: I can't get it to work with $[...] syntax as the variable is apparently empty at the initial.