参考链接：
https://www.cnblogs.com/weiyiming007/p/10675053.html
https://www.jianshu.com/p/40f698157330
获取dns解析时间
和linux中一样，使用curl命令可以获取dns解析时间，命令如下
curl -o /dev/null -s -w %{time_namelookup} http://www.baidu.com
Android中执行linux命令，代码如下：
String getdnstime(){
Runtime mRuntime = Runtime.getRuntime();
try {
//Process中封装了返回的结果和执行错误的结果
Process mProcess = mRuntime.exec("curl -o /dev/null -s -w %{time_namelookup} http://www.baidu.com");
BufferedReader mReader = new BufferedReader(new InputStreamReader(mProcess.getInputStream()));
StringBuffer mRespBuff = new StringBuffer();
char[] buff = new char[1024];
int ch = 0;
while ((ch = mReader.read(buff)) != -1) {
mRespBuff.append(buff, 0, ch);
}
mReader.close();
return mRespBuff.toString();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return "";
}
