Variables

Variables allow targets to share simple string values with downstream targets. Unlike parameters (which are inputs), variables are outputs produced during execution.

Producing a Variable

Declare and write a variable:

Target SetupVersion => t => t
    .ProducesVariable("BuildVersion")
    .Executes(async cancellationToken =>
    {
        var version = "1.2.3";
        await WriteVariable("BuildVersion", version, cancellationToken);
    });

WriteVariable is available via the IVariablesHelper interface.

Consuming a Variable

Declare that a target consumes a variable from another target:

Target Pack => t => t
    .ConsumesVariable(nameof(SetupVersion), "BuildVersion")
    .Executes(async cancellationToken =>
    {
        var version = await ReadVariable(nameof(SetupVersion), "BuildVersion", cancellationToken);
        Logger.LogInformation("Packing version {Version}", version);
    });

How Variables Work

• Locally, variables are stored in-memory and shared between targets in the same process.
• In workflows, variables are mapped to the platform's native mechanism (e.g. GitHub Actions job outputs, Azure DevOps pipeline variables) so they can cross job boundaries.

IVariableProvider

The framework uses IVariableProvider implementations to read and write variables. Multiple providers form a chain of responsibility:

public interface IVariableProvider
{
    Task<bool> WriteVariable(string variableName, string variableValue, CancellationToken ct);
    Task<bool> ReadVariable(string jobName, string variableName, CancellationToken ct);
}

The built-in AtomVariableProvider handles local execution. Platform modules (GitHub, DevOps) register their own providers for CI environments.

Next Steps

→ File System