Exemplo de uma ferramenta para debug.

watch.js

var spawn = require('child_process').spawn;
var fs = require('fs');
var args = process.argv.slice(2);
var program = null;
var filename = args[ 0 ];

function execHandler ( err, stdout, stderr ) {
  if ( err ) console.log( 'error: %s', err );
  if ( stdout ) console.log( 'stdout: ', stdout );
  if ( stderr ) console.log( 'stderr: %s', stderr );
}

function spawnDataHandler ( chunk ) {
  process.stdout.write( chunk.toString('utf-8') );
}

function programKillHandler () {
  if ( program ) { program.kill('SIGHUP'); }
}

function execFileHandler () {
  programKillHandler();
  program = spawn('node', [ filename ]);
  process.stdin.pipe( program.stdin );
  program.stdout.on('data', spawnDataHandler);
}

function fileWatchHandler ( curr, prev ) {
  execFileHandler();
  console.log( [ '\n', 'Restarted', '\n', curr.mtime, '\n' ].join('') );
}

function processExitHandler () {
  process.stdin.destroy();  
  programKillHandler();
}

(function main () {
  if ( filename ) {
    console.log('Watching the file: %s\n', filename);
    process.on('exit', processExitHandler);
    process.stdin.resume();
    execFileHandler();
    fs.watchFile( filename, fileWatchHandler );
  } else {
    process.exit( 1 );
  }
})();