a.go

func main() {
    var wg sync.WaitGroup
    currentWindow, e := exec.Command("xdotool", "getactivewindow").Output()
    if e != nil {
        fmt.Println(e)
    }

    cmd := exec.Command("xev", "-id", string(currentWindow), "-event", "property")
    if e != nil {
        fmt.Println(e)
    }
    stdout, e := cmd.StdoutPipe()
    cmd.Start()
    wg.Add(1)
    go func() {
        for {
            _, err := stdout.Read(make([]byte, 1))
            if err == nil {
                cols, _ := exec.Command("tput", "cols").Output()
                rows, _ := exec.Command("tput", "lines").Output()

                fmt.Println("columns: ", string(cols))
                fmt.Println("rows: ", string(rows))
            } else {
                wg.Done()
            }
        }
    }()
    wg.Wait()
    fmt.Println("dadasdasd")
}
/*
































































*/

a.js

var spawn = require('child_process').spawn
var spawnSync = require('child_process').spawnSync

const currentWindowID = spawnSync('xdotool', ['getactivewindow']).stdout.toString()

var xevent = spawn('xev', ['-id', currentWindowID.substr(0, currentWindowID.length - 1), '-event', 'property'])
/*                                               ^--- remove the newline from the end of the currentWindowID */

xevent.stdout.on('data', function (data) {
  console.log('cols', spawnSync('tput', ['cols']).stdout.toString())
  console.log('lines', spawnSync('tput', ['lines']).stdout.toString())
})

console.log('something else')
/*







































































*/

a.sh

function termSize() {
  xev -id $(xdotool getactivewindow) -event property | while read line
  do
    tput cols
    tput lines
  done
}

termSize &
echo "something else"
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