/**   * 保证单进程   *   * @param string $processName 进程名   * @param string $pidFile 进程文件路径   * @return boolean 是否继续执行当前进程   */  function singleProcess($processName, $pidFile)  {   if (file_exists($pidFile) && $fp = @fopen($pidFile,"rb"))   {    flock($fp, LOCK_SH);    $last_pid = fread($fp, filesize($pidFile));    fclose($fp);    if (!empty($last_pid))    {     $command = exec("/bin/ps -p $last_pid -o command=");     if ($command == $processName)     {      return false;     }    }   }   $cur_pid = posix_getpid();   if ($fp = @fopen($pidFile, "wb"))   {    fputs($fp, $cur_pid);    ftruncate($fp, strlen($cur_pid));    fclose($fp);    return true;   }   else   {    return false;   }  }  /**   * 获取当前进程对应的Command   *   * @return string 命令及其参数   */  function getCurrentCommand()  {   $pid     = posix_getpid();   $command = exec("/bin/ps -p $pid -o command=");   return $command;  }

if (singleProcess(getCurrentCommand(), 'path/to/script.pid')) {     // code goes here } else {  exit("Sorry, this script file has already been running ...\n"); }