packer/command/test-fixtures/build-variable-sharing/template.json

{
    "builders": [
        {
            "name": "chocolate",
            "type": "null",
            "communicator": "none"
        }
    ],
    "provisioners": [
        {
            "type": "shell-local",
            "inline": [
                "echo hi > provisioner.{{ build `ID`}}.txt"
            ]
        }
    ],
    "post-processors": [
        {
            "type": "shell-local",
            "inline": [
                "echo hi > post-processor.{{ build `ID`}}.txt"
            ]
        }
    ]
}