code: function match(self, dirname, basename, callback) {
    var pathname, stats, pattern, matches;
  
    pattern = patternFor(self, basename);
    matches = self.entries(dirname).filter(function(m) { return pattern.test(m); });
    matches = sortMatches(self, matches, basename);
  
    while (matches.length) {
      pathname  = path.join(dirname, matches.shift());
      stats     = self.stat(pathname);
  
      if (stats && stats.isFile() && callback(pathname)) {
        return pathname;
      }
    }
  }
docs: Checks if the path is actually on the file system and performs any syscalls if necessary.