child_process won't execute

[Temisola1]

I’m trying to execute a python script using the child_process. However my function doesn’t seem to be triggering.

const spawn = require("child_process").spawn
var NodeHelper = require("node_helper")
const process = spawn("python3", ["return_something.py"])

module.exports = NodeHelper.create({
  start: function() {
    this.countDown = 10000000
  },
  socketNotificationReceived: function(notification, payload) {
      switch(notification){
          case "DO_YOUR_JOB":
            console.log(payload)
            this.sendSocketNotification("I_DID", (this.countDown - payload))
            break
          case "RETRIEVE_DATA":
            console.log(payload)
            this.job()
            break
      }
  },
  job: function(){
    console.log("I'm trying to retrieve data")
    process.stdout.on('data', (data)=>{
      //********everything works up till here
        console.log("inside")
      var result = String.fromCharCode.apply(null, new Uint16Array((data)))
      this.sendSocketNotification("DATA_RETRIEVED", result)
    })
  }
})

Python script.

import sys

print("Hello, I'm Amira")

sys.stdout.flush()

[sdetweil]

how about like this

const spawn = require("child_process").spawn
var NodeHelper = require("node_helper")


module.exports = NodeHelper.create({
  start: function() {
    this.countDown = 10000000
  },
  socketNotificationReceived: function(notification, payload) {
      switch(notification){
          case "DO_YOUR_JOB":
            console.log(payload)
            this.sendSocketNotification("I_DID", (this.countDown - payload))
            break
          case "RETRIEVE_DATA":
            console.log(payload)
            this.job()
            break
      }
  },
  job: function(){
    console.log("I'm trying to retrieve data")
   var process = spawn("python3", ["return_something.py"])
    process.stdout.on('data', (data)=>{
      //********everything works up till here
        console.log("inside")
      var result = String.fromCharCode.apply(null, new Uint16Array((data)))
      this.sendSocketNotification("DATA_RETRIEVED", result)
    })
  }
})

[Temisola1]

@sdetweil thanks for the response. that doesn’t seem to be working either.
Is there something I need to install to be able to use stdout?

[sdetweil]

@Temisola1 i will look at it in the morning…

you are seeing the “I’m trying to retrieve data”

in the terminal window where you did npm start, right?

[Temisola1]

@sdetweil That is correct. It works up till that point.

[sdetweil]

@Temisola1 if you run this does it work from the terminal window?

testit.py

import sys 
# Takes first name and last name via command  
# line arguments and then display them 
print("Output from Python") 
print("First name: " ) 
print("Last name: " ) 

testit.js

  var spawn = require("child_process").spawn; 

    // Parameters passed in spawn - 
    // 1. type_of_script 
    // 2. list containing Path of the script 
    //    and arguments for the script  

    // E.g : http://localhost:3000/name?firstname=Mike&lastname=Will 
    // so, first name = Mike and last name = Will 
    var process = spawn('python3',["./testit.py"]); 
   //                         req.query.firstname, 
     //                       req.query.lastname] ); 
  
    // Takes stdout data from script which executed 
    // with arguments and send this data to res object 
    process.stdout.on('data', (data)=> { 
        console.log("received " +data); 
    } ) 

works for me… (note python script path is ./, make sure u have right path to py file)

then do
node testit.js

[Temisola1]

@sdetweil said in child_process won't execute:

node testit.js

Yes, that works in the console.

[Temisola1]

@sdetweil So I tried putting in the full path in my node_helper as opposed to relative path and that seemed to work. is there a way I can log the current directory in nodejs. It seems that’s the issue

[Temisola1]

@sdetweil after running successfully a few times it now returns Buffer 48 45 5c… or something that looks like hexadecimal code

[sdetweil]

@Temisola1 the node_helper doesn’t know where it is… but the Modulename does…

this.path

so, you can add that to the config info you send down in the typical

sendSocketNotification(“somevalue”, this.config)

to pass parameters to the node_helper

[sdetweil]

@Temisola1 said in child_process won't execute:

after running successfully a few times it now returns

u need to cleanup when the invoked process ends

process.on('exit', function() {
  if (x) {
    x.kill();
  }
});

[joshwilsonvu]

@sdetweil I just want to recommend the execa package as it solves some issues with “child_process,” like cleaning up when the process exits.

[Temisola1]

Thank you all for all your wonderful suggestions. I’m able to run my python script successfully now. Thanks!