Node-Red subflow creating a subflow node that functions as an async version of the built-in exec node with stdin support

subflow_exec_stdin_async.json

[
    {
        "id": "6ea632aca2282da9",
        "type": "subflow",
        "name": "exec stdin",
        "info": "## Inputs \r\n\r\nSimilar to the exec node this starts a process.\r\nThe input message format is as follows:\r\n\r\n```js\r\nmsg = {\r\n    topic: \"<command to be executed>\",\r\n    timeout: <timeout in milliseconds before process is killed>,\r\n    payload: <passed to stdin:optional>\r\n}\r\n```\r\n\r\n## Outputs\r\n\r\nThe first output contains error message from the underlying\r\nnode.js functionality (if any).\r\n\r\nThe second output contains stdout output.\r\n\r\nThe third output contains stderr output.",
        "category": "function",
        "in": [
            {
                "x": 60,
                "y": 80,
                "wires": [
                    {
                        "id": "0c0c99c7af618215"
                    }
                ]
            }
        ],
        "out": [
            {
                "x": 760,
                "y": 80,
                "wires": [
                    {
                        "id": "0c0c99c7af618215",
                        "port": 0
                    }
                ]
            },
            {
                "x": 770,
                "y": 140,
                "wires": [
                    {
                        "id": "0c0c99c7af618215",
                        "port": 1
                    }
                ]
            },
            {
                "x": 770,
                "y": 200,
                "wires": [
                    {
                        "id": "0c0c99c7af618215",
                        "port": 2
                    }
                ]
            }
        ],
        "env": [],
        "meta": {},
        "color": "#dc8e6b",
        "inputLabels": [
            "cmd stdin"
        ],
        "outputLabels": [
            "err",
            "stdout",
            "stderr"
        ],
        "icon": "node-red/cog.svg"
    },
    {
        "id": "0c0c99c7af618215",
        "type": "function",
        "z": "6ea632aca2282da9",
        "name": "exec",
        "func": "var exec = childProcess.exec;\n\nvar child = exec(msg.topic, \n    {\n        timeout: msg.timeout\n    },\n    function (err,stdout,stderr) {\n        node.send({ payload: err });\n        node.send([null, Object.assign({}, msg, { \n            payload: stdout \n        })]);\n        node.send([null, null, Object.assign({}, msg, {\n            payload: stderr\n        })]);\n    });\n\nvar stdinStream = new stream.Readable();\nif( msg.hasOwnProperty(\"payload\") && msg.payload != null)\n{\n    stdinStream.push(msg.payload.toString());  // Add data to the internal queue for users of the stream to consume\n    stdinStream.push(null);   // Signals the end of the stream (EOF)\n    stdinStream.pipe(child.stdin);\n}",
        "outputs": 3,
        "noerr": 0,
        "initialize": "",
        "finalize": "",
        "libs": [
            {
                "var": "childProcess",
                "module": "child_process"
            },
            {
                "var": "stream",
                "module": "stream"
            }
        ],
        "x": 530,
        "y": 80,
        "wires": [
            [],
            [],
            []
        ]
    }
]