drush alias lookup

drushrc.php

<?php
function findFiles($base_dir, $asset_dir, $extensions = array()) {
  function glob_recursive($base_dir, &$directories = array()) {
    foreach(glob($base_dir, GLOB_ONLYDIR | GLOB_NOSORT) as $folder) {
      $directories[] = $folder;
      glob_recursive("{$folder}/*", $directories);
    }
  }
  glob_recursive($base_dir, $directories);
  $files = array();
  foreach ($directories as $base_dir) {
    if (strpos($base_dir, $asset_dir) != FALSE) {
      foreach ($extensions as $extension) {
        foreach (glob("{$base_dir}/*.{$extension}") as $file) {
          $files[$base_dir] = $base_dir;
        }
      }
    }
  }
  return $files;
}
$paths = drush_get_context('ALIAS_PATH');
$file_cache = dirname(__FILE__) . '/drush_alias_paths.txt';
if (!file_exists($file_cache)) {
  $cached_paths = findFiles("/var/www", 'drush', array("drushrc.php"));
  file_put_contents($file_cache, implode(PHP_EOL, $cached_paths), FILE_APPEND);
  $paths = array_merge((array) $paths, (array) $cached_paths);
}
else {
  $cached_paths = explode("\n", file_get_contents(dirname(__FILE__) . '/drush_alias_paths.txt'));
  $paths = array_merge((array) $paths, (array) $cached_paths);
}

drush_set_context('ALIAS_PATH', $paths);