Demystifying Azure DevOps Predefined Variables on MacOS Build Agents

14.11.2020 — Code, DevOps — 2 min read

As a frequent user of Azure DevOps, crafting a Build Pipeline is often a task reserved for the initial setup phase rather than daily routine. However, when the need arises to execute builds on a MacOS Agent, the process can introduce a new set of considerations. Fortunately, leveraging the predefined variables provided by Azure DevOps can streamline this process and provide valuable insights into the environment.

One of the notable advantages of utilizing hosted Agents from Microsoft is the alleviation of responsibilities such as updates and maintenance, allowing users to focus solely on their development tasks. In this context, understanding and harnessing the predefined variables specific to MacOS Build Agents can significantly enhance the efficiency and effectiveness of build processes.

To gain a comprehensive understanding of these variables, let's examine a simple script task that outputs them:

- task: Bash@3
  inputs:
    targetType: 'inline'
    script: |
      echo 'agent.homeDirectory: $(agent.homeDirectory)'
      echo 'agent.buildDirectory: $(agent.buildDirectory)'
      echo 'agent.tempDirectory: $(agent.tempDirectory)'
      echo 'agent.toolsDirectory: $(agent.toolsDirectory)'
      echo 'agent.workFolder: $(agent.workFolder)'
      echo 'agent.workFolder: $(agent.workFolder)'
      echo 'build.artifactStagingDirectory: $(build.artifactStagingDirectory)'
      echo 'build.binariesDirectory: $(build.binariesDirectory)'
      echo 'build.sourcesDirectory: $(build.sourcesDirectory)'
      echo 'build.stagingDirectory: $(build.stagingDirectory)'
      echo 'system.defaultWorkingDirectory: $(system.defaultWorkingDirectory)'

Upon execution on a MacOS Agent, the results are as follows:

agent.homeDirectory: /Users/runner/runners/2.174.2
agent.buildDirectory: /Users/runner/work/1
agent.tempDirectory: /Users/runner/work/_temp
agent.toolsDirectory: /Users/runner/hostedtoolcache
agent.workFolder: /Users/runner/work
agent.workFolder: /Users/runner/work
build.artifactStagingDirectory: /Users/runner/work/1/a
build.binariesDirectory: /Users/runner/work/1/b
build.sourcesDirectory: /Users/runner/work/1/s
build.stagingDirectory: /Users/runner/work/1/a
system.defaultWorkingDirectory: /Users/runner/work/1/s
```
These variables provide crucial information about the agent's environment, such as directories for build artifacts, binaries, sources, and staging. Understanding and utilizing these variables within your build pipeline can enable dynamic and efficient configuration, facilitating seamless integration with the MacOS Build Agent environment.

In conclusion, while configuring build pipelines for MacOS Agents in Azure DevOps may initially seem daunting, leveraging predefined variables simplifies the process significantly. By incorporating these variables into your pipeline scripts, you can optimize your build workflows and ensure smooth execution across different agent environments.