how to return something..like true or false to widget??

[MrbeanN513]

void initState() {
timer = Timer.periodic(Duration(seconds: 10), (Timer t) {
setState(() {

    var hello =shell.run("find 123");
    if (hello == true) {
      print("hahahahahhahahahah2");
    }
  });

[ERROR:flutter/lib/ui/ui_dart_state.cc(186)] Unhandled Exception: ShellException(cat 123 |grep hello, exitCode 1, workingDirectory: /home/kali/lkj)

if find 123 file then signaling true to flutter widget. and print something.........
how to return something from shell??