How to get the current operating system in MSBuild?

Question

I have a .NET Core 1.1 console project created with Visual Studio 2017. After building the project, I need to run a powershell script so I added the following to the MyProject.csproj file:

<Target Name="PostcompileScript" AfterTargets="Build">
    <Exec Command="execute-tasks.ps1" />
</Target>

Now I need to build the project in a Linux environment, I need to instruct MSBuild to run execute-tasks.sh instead of execute-tasks.ps1 when it is running in Linux.

I believe this is achievable via the Condition attribute, but is there an MSBuild variable that holds the operating system name?

Answer 1

Using $(OS), as documented in other answers, can distinguish between Windows_NT and Unix (which includes both Linux and macOS), but not between different Unix-like systems. If you are using MSBuild 15.3 or later (which is very likely), you may want to consider using [MSBuild]::IsOsPlatform():

<Exec Command="./foo.sh" Condition="$([MSBuild]::IsOSPlatform('Linux'))" />

The argument can be the name of any OsPlatform member.

Answer 2

The variable is $(OS), usually checked against being or not being Windows_NT:

<Exec Command="./foo.sh" Condition=" '$(OS)' != 'Windows_NT' " />