Multiplatform Builds

Building for Multiple Platforms

Often you will want your code to run on multiple operating systems and architectures. For example, you might want to build binaries or docker images that run both on Linux amd64 and MacOS arm64. Grog has one built-in solution for this: platform selectors.

Platform Selectors

Grog’s platform selectors allow you to define targets that only run on specific platforms. When a target doesn’t match the current host’s platform, Grog will skip it automatically.

Defining Platform Selectors

You can specify platform requirements using the platforms field:

default_platforms:
  - linux/amd64

targets:
  # default_platforms is applied here
  - name: build_linux_amd64
    command: go build -o dist/myapp-linux-amd64 ./cmd/myapp
    inputs:
      - cmd/**/*.go
      - go.mod
    outputs:
      - dist/myapp-linux-amd64

  - name: build_darwin_arm64
    command: go build -o dist/myapp-darwin-arm64 ./cmd/myapp
    # This overrides default_platforms
    platforms:
      - darwin/arm64
    inputs:
      - cmd/**/*.go
      - go.mod
    outputs:
      - dist/myapp-darwin-arm64

In this example:

build_linux_amd64 will only run on Linux AMD64 hosts
build_darwin_arm64 will only run on macOS ARM64 hosts (like Apple Silicon Macs)

Each entry in platforms must be a full os/arch identifier. To support multiple variants for the same target, list each supported identifier.

Platform Selector Behavior

When you run grog build, Grog will:

Check each target’s platform selectors against the os/arch platform the grog binary was built for
Skip targets that don’t match the current platform
Build targets that do match the platform

This allows you to define all platform variants in a single build file, but only build the ones appropriate for the current environment.

Skipping platform selectors

There may be scenarios where you want to skip platform selectors. To do so, pass the --all-platforms, (shorthand: -a) flag to build and querying commands.

Handling Dependencies with Platform Selectors

When a target depends on a platform-specific target, Grog enforces platform compatibility:

targets:
  - name: linux_binary
    command: go build -o dist/myapp-linux ./cmd/myapp
    platforms:
      - linux/amd64
    outputs:
      - dist/myapp-linux

  - name: package_linux
    dependencies:
      - :linux_binary
    command: tar -czf dist/myapp-linux.tar.gz dist/myapp-linux
    platforms:
      - linux/amd64
    outputs:
      - dist/myapp-linux.tar.gz

If you try to build package_linux on a non-Linux platform, Grog will fail with an error because the dependency linux_binary cannot be built on the current platform.