/**
 * 执行相关的命令
 */
public String execCmd(String command) throws Exception {
    ChannelExec channelExec = null;
    InputStream in = null;
    StringBuffer buf = null;
    try {
       channelExec = (ChannelExec) session.openChannel("exec");
       channelExec.setCommand(command);
       channelExec.setInputStream(null);
       channelExec.setErrStream(System.err);
       in = channelExec.getInputStream();
       channelExec.connect();
       int res = -1;
       buf = new StringBuffer(1024);
       byte[] tmp = new byte[1024];
       while (true) {
         while (in.available() > 0) {
          int i = in.read(tmp, 0, 1024);
          if (i < 0)
              break;
          buf.append(new String(tmp, 0, i));
         }
         if (channelExec.isClosed()) {
          res = channelExec.getExitStatus();
          System.out.println(format("Exit-status: %d", res));
          break;
         }
       }
    } finally {
       if (channelExec != null) {
         channelExec.disconnect();
         channelExec = null;
       }
       if (in != null) {
         try {
          in.close();
         } catch (IOException e) {
          LOG.debug(e);
         }
         in = null;
       }
    }
    return buf.toString();
}