packer/command/test-fixtures/var-arg/fruit_builder.json

{
    "variables": {
        "fruit": null
    },
    "builders": [
        {
            "communicator": "none",
            "type": "null"
        }
    ],
    "post-processors": [
        [
            {
                "name": "apple",
                "type": "shell-local",
                "inline": [ "echo {{ user `fruit` }} > {{ user `fruit` }}.txt" ]
            }
        ]
    ]
}