如何在android中录制屏幕时以编程方式实时获取/显示文件大小

我的录音代码如下

List<String> videotrack = new LinkedList<String>();

while (videoRecordContinue) {

Long tsLong = System.currentTimeMillis() / 1000;
path = "/myTest.mp4";

videotrack.add(path);

Process proc;

proc = Runtime.getRuntime().exec("screenrecord --size 720x1280 --bit-rate 2000000" 
       + Environment.getExternalStorageDirectory().getAbsolutePath() + videoPath);

proc.waitFor();

}

如何实时检查编码大小