var util = require("util"), childProcess = require("child_process"); 
function next(i){ 
if (i <= 0) return ; 
var child = childProcess.spawn("echo", ["hello"] ); 
child.stdout.addListener("data", function (chunk){ 
util.print(chunk); 
} 
); 
child.addListener("exit", function (code){ 
if (code != 0) process.exit(-1); 
next(i - 1); 
} 
); 
} 
next(500);