Function return not work

General
1

Hi all, I'm writing a function in func-exec node

msg.topic = ""
var array = [];

var exec = child_process.exec('pgrep firefox', (error, stdout, stderr) => {
    if (error) { 
        console.info("false")
        msg.payload = false 
        msg.topic = "error connection ui"
        return msg;
    } 
    if (stdout != ""){
        var splitString = stdout.split(" ")
        for (var i = 0; i < splitString.length; i++){
            array.push(parseInt(splitString[i]))
        }
        console.info(array)
        msg.payload = array
    }
}); 
console.info(msg.payload)
return msg;

unfortunately the msg.payload is always undefined while array is corrected not empty as I can see on the console.

can some help me to understand where I wrong?
many thanks

2

does the second if () require a return?

3

Hi @denissanga

You cannot use return to send a message from inside a callback function - you can only use return at the top level of the code.

To send a message from inside a callback, you need to use node.send(msg) - Writing Functions : Node-RED

4

many thanks

I try with this

msg.topic = ""
var array = [];

var exec = child_process.exec('pgrep firefox', msg, (error, stdout, stderr) => {
    if (error) { 
        console.info("false")
        msg.payload = false 
        msg.topic = "error connection ui"
        node.send(msg)
    } 
    if (stdout != ""){
        var splitString = stdout.split(" ")
        for (var i = 0; i < splitString.length; i++){
            array.push(parseInt(splitString[i]))
        }
        console.info("out1  " + array)
        msg.payload = array
        node.send(msg)
    }
}); 


console.info("out2  " + msg.payload)
return msg;

but I obtain
out1 123345
out2 true

5

What do you expect to get?

If you only want it to send a message once the exec has finished, then delete the return msg line at the end.

6

I would obtain 123345...there is no way with this approach?

7

I do not understand what you mean.

You have said you are getting:

out1 12324123

That tells us the console.info you have inside the callback is being called... so we can assume the next two lines are also being called which will cause a message to be sent:

msg.payload = array
node.send(msg)

Have you connected a Debug node to the output of the Function to see what message it is sending?

8

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