node.js child_process sample

child.js

//var child = process.createChildProcess('sh',
//      ['-c', 'echo hello; sleep 1; echo world;']);
//child.addListener('data', function(chunk) {
//      console.log(chunk);
//});

var spawn  = require('child_process').spawn,
    child = spawn('sh', ['-c', 'echo hello; sleep 1; echo world;']);

child.stdout.on('data', function(chunk) {
        console.log(chunk.toString());
});

child.on('exit', function(code) {
        console.log('child process exited with code' + code);
});

I don't understand please give me more example