How to make normal function to be returning in node.js

Question

    function puts(error, stdout, stderr) {
    if (error) {
        console.log("error", "Error connecting");
        result = "Failed";
        console.log(result)
    }
    else {
        sys.puts(stdout)
        result = "Success"
        console.log(result)
    }
    }

//The calling function is mentioned as below:
app.get('/api/platforms1', function(req, res){
    exec("ping localhost",puts);
});

//I am working under mean stack.I have created a method to ping ip address and display their result.But now I want to display the result as a return function.How can we do it??

I'm not sure what you mean by "display the result as a return function." Could you explain? — Aaron N. Brock, Mar 29 '17 at 06:55
The function as you can see "puts" .I want to return the value "result".Whenever we call the function as "exec(ping localhost,puts)" — vinay, Mar 29 '17 at 07:02
Perhaps what you're looking for is here [How to return the response from an asynchronous call](http://stackoverflow.com/questions/14220321/how-do-i-return-the-response-from-an-asynchronous-call). — jfriend00, Mar 29 '17 at 07:08

abdulbarik · Answer 1 · 2017-03-29T07:20:57.657

0

First of all sys is deprecated you can use util instead of it.

And if you want to get your result wherever, that thing you can do with callback, since Node.js nature is asynchronous.

edited Mar 29 '17 at 07:20

answered Mar 29 '17 at 07:11

abdulbarik

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score 0 · Accepted Answer · edited May 23 '17 at 12:25

First:

In windows, if you use:

ping google.com

You will get only 4 information ping, but on Ubuntu, if you use that command, the ping can't stop until you stop it with Ctrl+C.

To fix this we need to use -c flag. The -c option tells ping program to stop after sending (or receiving) specified number of ECHO_RESPONSE packets.

Second:

you need to use res.send to send back the ping response but due to your callback function i.e puts you don't have the access for res and req.

Use this wrapper func to pass another arguments you want to access with your callback

function execute(command, callback, res) {
    exec(command, function(error, stdout, stderr) {
        // Notice extra params I have passed here^,  ^
        callback(error, stdout, stderr, res);
    });
}

and you can use this as

    execute("ping -c 2 google.com", puts, /*pass extra params*/ res);

and catch extra params here after your callback function

                                    || 
                         ---------- \/

function execute(command, callback, res) {
  ...
}

Complete code:

var exec = require('child_process').exec;

function puts(error, stdout, stderr, res) {
        // Notice extra params here  ^
    if (error) {
        console.log("error", "Error connecting");
        result = "Failed";
        console.log(result)
    } else {
        sys.puts(stdout)
        result = "Success"
        console.log(result)
        //send response to client
        res.send(result)
    }
}

//The calling function is mentioned as below:
app.get('/api/platforms1', function(req, res) {
    execute("ping -c 1 google.com", puts, /*pass extra params*/ res);
});

function execute(command, callback, res) {
    exec(command, function(error, stdout, stderr) {
        // Notice extra params I have passed here^,  ^
        callback(error, stdout, stderr, res);
    });
}

Ref:

https://askubuntu.com/questions/200989/ping-for-4-times

Get the output of a shell command in node.js

How to make normal function to be returning in node.js

2 Answers2