Child Process tests to run `gcloud app deploy` with realtime feedback

child_process-1-pipe.js

const which = require("which")
const childProcess = require("child_process")

let bin = `gcloud${/^win/.test(process.platform) ? '.cmd' : ''}`
which(bin, (err, fullpath) => {
    if (err) {
        return console.log(err)
    }
    console.log(`${bin} has been detected:\n${fullpath}`)
    let proc = childProcess.spawn(fullpath, ['app', 'deploy'], {
        stdio: "pipe"
    })
    proc.stdout.on("data", data => console.log(`stdout: ${data.toString()}`))
    proc.stderr.on("data", err => console.log(`stderr: ${err.toString()}`))
    proc.on("close", (code) => {
        console.log("program terminated with code: ", code)
    })
})

/*
It seems, I only have stderr without stdout:

C:\cygwin64\home\thyb\test>node index.js
gcloud.cmd has been detected:
C:\Users\thyb\google-cloud-sdk-159.0.0-windows-x86_64-bundled-python\google-cloud-sdk\bin\gcloud.cmd
stderr: WARNING: Automatic app detection is currently in Beta
*/

child_process-2-file.js

const which = require("which")
const childProcess = require("child_process")
const fs = require("fs")
const consts = require('constants');

function readFrom(fd, start) {		
 	let cont = true		
 	let lines = ''		
 	while (cont) {		
 		let chunk = new Buffer(1024)		
 		let len = fs.readSync(fd, chunk, 0, 1024, start)		
 		lines += chunk.toString().substr(0, len)		
 		start += len		
	
 		if (len < 1024) {		
 			cont = false		
 		}		
 	}		
 	return {		
 		lines: lines,		
 		end: start		
 	}		
 }

let bin = `gcloud${/^win/.test(process.platform) ? '.cmd' : ''}`
which(bin, (err, fullpath) => {
    if (err) {
        return console.log(err)
    }
    fs.writeFileSync("deploy.log", "")
    let fd = fs.openSync("deploy.log", consts.O_RDWR)
    let pos = 0;
    const parseLogs = () => {
        let res = readFrom(fd, pos)
        pos = res.end
        if (res.lines.length) {
            console.log(`output: ${res.lines}`)
        }
    }

    console.log(`${bin} has been detected:\n${fullpath}`)
    let proc = childProcess.spawn(fullpath, ['app', 'deploy'], {
        stdio: ["pipe", fd, fd]
    })

    let interval = setInterval(() => parseLogs(), 500)

    proc.on("close", (code) => {
        clearInterval(interval)
        fs.closeSync(fd)
        let res = readFrom(fd, pos)
        pos = res.end
        console.log(res.lines + "\n")
        console.log("program terminated with code: ", code)
    })
})

/**
This workaround was used to workaround the 200kb buffer limit. Works on Mac OS X fully but not on Windows:

C:\cygwin64\home\thyb\test>node index.js
gcloud.cmd has been detected:
C:\Users\thyb\google-cloud-sdk-159.0.0-windows-x86_64-bundled-python\google-cloud-sdk\bin\gcloud.cmd
output: WARNING: Automatic app detection is currently in Beta
*/

child_process-3-stdout.js

const which = require("which")
const childProcess = require("child_process")

let bin = `gcloud${/^win/.test(process.platform) ? '.cmd' : ''}`
which(bin, (err, fullpath) => {
    if (err) {
        return console.log(err)
    }
    console.log(`${bin} has been detected:\n${fullpath}`)
    let proc = childProcess.spawn(fullpath, ['app', 'deploy'], {
        stdio: ["pipe", process.stdout, process.stderr]
    })
    proc.on("close", (code) => {
        console.log("program terminated with code: ", code)
    })
})

/*
=> works (display logs in console) but I can't read stdout/stderr in realtime from the application (cf child_process-4-stdout-bis.js)

C:\cygwin64\home\thyb\test>node index.js
gcloud.cmd has been detected:
C:\Users\thyb\google-cloud-sdk-159.0.0-windows-x86_64-bundled-python\google-cloud-sdk\bin\gcloud.cmd
WARNING: Automatic app detection is currently in Beta
Deployment to Google App Engine requires an app.yaml file. This command will run `gcloud beta app gen-config` to generate an app.yaml file for you in the current directory (if the current directory does not contain an App Engine service, please answer "no").

Do you want to continue (Y/n)?
*/

child_process-4-stdout-bis.js

const which = require("which")
const childProcess = require("child_process")

let bin = `gcloud${/^win/.test(process.platform) ? '.cmd' : ''}`
which(bin, (err, fullpath) => {
    if (err) {
        return console.log(err)
    }
    console.log(`${bin} has been detected:\n${fullpath}`)
    let proc = childProcess.spawn(fullpath, ['app', 'deploy'], {
        stdio: ["pipe", process.stdout, process.stderr]
    })
    process.stdout.on('data', data => console.log(`stdout: ${data}`))
    process.stderr.on('data', data => console.log(`stderr: ${data}`))

    proc.on("close", (code) => {
        console.log("program terminated with code: ", code)
    })
})

/**
C:\cygwin64\home\thyb\test>node index.js
gcloud.cmd has been detected:
C:\Users\thyb\google-cloud-sdk-159.0.0-windows-x86_64-bundled-python\google-cloud-sdk\bin\gcloud.cmd

events.js:163
      throw er; // Unhandled 'error' event
      ^

Error: read ENOTCONN
    at exports._errnoException (util.js:1033:11)
    at WriteStream.Socket._read (net.js:437:21)
    at WriteStream.Readable.read (_stream_readable.js:348:10)
    at WriteStream.Socket.read (net.js:320:43)
    at resume_ (_stream_readable.js:737:12)
    at _combinedTickCallback (internal/process/next_tick.js:80:11)
    at process._tickCallback (internal/process/next_tick.js:104:9)
*/