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cross-platform-scripting.md

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title ms.custom description ms.topic ms.assetid ms.date monikerRange
Cross-platform scripting
seodec18
Patterns for safe cross-platform scripting
conceptual
96b7da24-617e-4a58-b65f-040c374e60e2
02/28/2022
<= azure-devops

Run cross-platform scripts

[!INCLUDE version-lt-eq-azure-devops]

With Azure Pipelines, you can run your builds on macOS, Linux, and Windows machines. If you develop on cross-platform technologies such as .NET Core, Node.js and Python, these capabilities bring both benefits and challenges.

For example, most pipelines include one or more scripts that you want to run during the build process. But scripts often don't run the same way on different platforms. Below are some tips on how to handle this kind of challenge.

Run cross-platform tools with a script step

The script keyword is a shortcut for the command line task. The script keyword runs Bash on Linux and macOS and cmd.exe on Windows.

Using script can be useful when your task just passes arguments to a cross-platform tool. For instance, calling npm with a set of arguments can be easily accomplished with a script step. script runs in each platform's native script interpreter: Bash on macOS and Linux, cmd.exe on Windows.

YAML

steps:
- script: |
    npm install
    npm test

Classic

  1. Add a Command Line task to your pipeline.

  2. Replace the body of the script with:

    npm install
npm test

Handle environment variables

Environment variables throw the first wrinkle into writing cross-platform scripts. Command line, PowerShell, and Bash each have different ways of reading environment variables. If you need to access an operating system-provided value like PATH, you'll need different techniques per platform.

However, Azure Pipelines offers a cross-platform way to refer to variables that it knows about called macro syntax. By surrounding a variable name in $( ), it will be expanded before the platform's shell ever sees it. For instance, if you want to echo out the ID of the pipeline, the following script is cross-platform friendly:

YAML

steps:
- script: echo This is pipeline $(System.DefinitionId)

This also works for variables you specify in the pipeline.

variables:
  Example: 'myValue'

steps:
- script: echo The value passed in is $(Example)

Classic

  1. Add a Command Line task to your pipeline.

  2. Replace the body of the script with:

    echo This is pipeline $(System.DefinitionId)

Consider Bash or pwsh

If you have more complex scripting needs than the examples shown above, then consider writing them in Bash. Most macOS and Linux agents have Bash as an available shell, and Windows agents include Git Bash or Windows Subsystem for Linux Bash. ::: moniker range=">=azure-devops-2020" For Azure Pipelines, the Microsoft-hosted agents always have Bash available. ::: moniker-end

For example, if you need to make a decision about whether your build is triggered by a pull request:

YAML

trigger:
    batch: true
    branches:
        include:
        - main
steps:
- bash: |
    echo "Hello world from $AGENT_NAME running on $AGENT_OS"
    case $BUILD_REASON in
            "Manual") echo "$BUILD_REQUESTEDFOR manually queued the build." ;;
            "IndividualCI") echo "This is a CI build for $BUILD_REQUESTEDFOR." ;;
            "BatchedCI") echo "This is a batched CI build for $BUILD_REQUESTEDFOR." ;;
        *) $BUILD_REASON ;;
    esac
  displayName: Hello world

Classic

  1. Add a Bash task to your pipeline.

  2. For the Type, select Inline.

  3. Replace the body of the script with:

    if [ -n "$SYSTEM_PULLREQUEST_PULLREQUESTNUMBER" ]; then
 echo This is for pull request $SYSTEM_PULLREQUEST_PULLREQUESTNUMBER
else
 echo This is not a pull request build. The trigger was $BUILD_REASON
fi

PowerShell Core (pwsh) is also an option. It requires each agent to have PowerShell Core installed.

Switch based on platform

In general, we recommend that you avoid platform-specific scripts to avoid problems such as duplication of your pipeline logic. Duplication causes extra work and extra risk of bugs. However, if there's no way to avoid platform-specific scripting, then you can use a condition to detect what platform you're on.

For example, suppose that for some reason you need the IP address of the build agent. On Windows, ipconfig gets that information. On macOS, it's ifconfig. And on Ubuntu Linux, it's ip addr.

Set up the below pipeline, then try running it against agents on different platforms.

YAML

steps:
# Linux
- bash: |
    export IPADDR=$(ip addr | grep 'state UP' -A2 | tail -n1 | awk '{print $2}' | cut -f1  -d'/')
    echo "##vso[task.setvariable variable=IP_ADDR]$IPADDR"
  condition: eq( variables['Agent.OS'], 'Linux' )
  displayName: Get IP on Linux
# macOS
- bash: |
    export IPADDR=$(ifconfig | grep 'en0' -A3 | grep inet | tail -n1 | awk '{print $2}')
    echo "##vso[task.setvariable variable=IP_ADDR]$IPADDR"
  condition: eq( variables['Agent.OS'], 'Darwin' )
  displayName: Get IP on macOS
# Windows
- powershell: |
    Set-Variable -Name IPADDR -Value ((Get-NetIPAddress | ?{ $_.AddressFamily -eq "IPv4" -and !($_.IPAddress -match "169") -and !($_.IPaddress -match "127") } | Select-Object -First 1).IPAddress)
    Write-Host "##vso[task.setvariable variable=IP_ADDR]$IPADDR"
  condition: eq( variables['Agent.OS'], 'Windows_NT' )
  displayName: Get IP on Windows

# now we use the value, no matter where we got it
- script: |
    echo The IP address is $(IP_ADDR)

Classic

First, add a Linux script.

  1. Add a Bash task to your pipeline.

  2. Set the Type to Inline.

  3. Replace the body of the script with:

    export IPADDR=$(ip addr | grep 'state UP' -A2 | tail -n1 | awk '{print $2}' | cut -f1  -d'/')
echo ##vso[task.setvariable variable=IP_ADDR]$IPADDR

  4. Change the value of Run this task to "Custom conditions".

  5. In the Custom condition field that appears, enter "eq( variables['Agent.OS'], 'Linux' )".

Next, add a macOS script.

  1. Repeat the above steps, but for the body of the script, enter:

    export IPADDR=$(ifconfig | grep 'en0' -A3 | tail -n1 | awk '{print $2}')
echo ##vso[task.setvariable variable=IP_ADDR]$IPADDR

  2. For the Custom condition, enter "eq( variables['Agent.OS'], 'Darwin' )".

Next, add a Windows script.

  1. Add a PowerShell task to your pipeline.

  2. Set the Type to Inline.

  3. Replace the body of the script with:

    Set-Variable -Name IPADDR -Value (Get-NetIPAddress | ?{ $_.AddressFamily -eq "IPv4" -and !($_.IPAddress -match "169") -and !($_.IPaddress -match "127") }).IPAddress
Write-Host ##vso[task.setvariable variable=IP_ADDR]$env:IPADDR

  4. Change the value of Run this task to "Custom conditions".

  5. In the Custom condition field that appears, enter "eq( variables['Agent.OS'], 'Windows_NT' )".

Finally, add a task that uses the value, no matter how we got it.

  1. Add a Command line task to your pipeline.

  2. Replace the body of the task with:

    echo The IP address is $(IP_ADDR)