android shell commands getting the result

Question

I work on an application that can make ping or traceroute requests from the android shell and my application reads the result and post it to the user. My problem is that I can not get the whole result (message) from the command. For example, the traceroute displays the initial message just before showing the HOPS and ping only works for 1 packet properly. Otherwise (for many packets) I get the initial part of ping request and not the results. I have a rooted device and installed busybox in order to have traceroute command.

The code is the following

    package com.example.commandshelltest;

import java.io.DataOutputStream;
import java.io.IOException;
import java.io.InputStream;

import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.widget.TextView;

public class MainActivity extends Activity {

    TextView tv1;
    String out = new String();
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);
    String result=execute_reboot();
    TextView tv1=(TextView)findViewById(R.id.textView1);
    //tv1.setText(Integer.toString(result.length())); // i can see that while increasing the number of icmp packets in ping the length stays the same
    tv1.setText(result);

    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

    String execute_reboot()
    {
        Process process1;
        try {
            int BUFF_LEN =1024;
            process1=Runtime.getRuntime().exec("su");
              DataOutputStream os = 
                  new DataOutputStream(process1.getOutputStream());
                //os.writeBytes("traceroute 8.8.8.8\n");
                os.writeBytes("ping -c 1 8.8.8.8\n");
                os.flush();
                InputStream stdout = process1.getInputStream();
                byte[] buffer = new byte[BUFF_LEN];
                int read;

                while((read=stdout.read(buffer))>0)
                while(true){
                    read = stdout.read(buffer);
                    out += new String(buffer, 0, read);
                    if(read<BUFF_LEN){
                        //we have read everything
                        break;
                    }
                }

                  os.writeBytes("exit\n");
                  os.flush();

                process1.waitFor();

        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return out;

    }

}

score 2 · Accepted Answer · edited May 23 '17 at 12:06

For everyone having the same problem.... I used as a code the example from Run shell commands from android program The use of threads and sleep time solved the problem for me

public void runAsRoot(String[] cmds) throws Exception {
        Process p = Runtime.getRuntime().exec("su");
        DataOutputStream os = new DataOutputStream(p.getOutputStream());
        InputStream is = p.getInputStream();
        for (String tmpCmd : cmds) {
            os.writeBytes(tmpCmd+"\n");
            int readed = 0;
            byte[] buff = new byte[4096];
            boolean cmdRequiresAnOutput = true;
            if (cmdRequiresAnOutput) {
                while( is.available() <= 0) {
                    try { Thread.sleep(5000); } catch(Exception ex) {}
                }

                while( is.available() > 0) {
                    readed = is.read(buff);
                    if ( readed <= 0 ) break;
                    String seg = new String(buff,0,readed);   
                    result=seg; //result is a string to show in textview
                }
            }
        }        
        os.writeBytes("exit\n");
        os.flush();

the important part is the Thread.sleep(5000); For "ls" the sleep time is not important. But for commands like ping or traceroute you need time and you have to wait for the results, hence 5000ms=5seconds is enough to get a response for a ping HOP.

the if(cmdRequiresAnoutput) is redundant.... If you remove it, it still works like charm — malcolm the4, May 15 '13 at 12:52

score 0 · Answer 2 · answered May 14 '13 at 21:58

0

You can't be sure that this is true:

                 if(read<BUFF_LEN){
                     //we have read everything
                     break;

The implementation may return before the buffer is filled entirely to avoid too long waiting.

Additionally the line

            while((read=stdout.read(buffer))>0)

may eat up some parts of the input. I don't understand what it is good for.

answered May 14 '13 at 21:58

Michael Butscher

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I understand that I have a problem with the buffer. How should I define the buffer to read the whole result (until everything is done) ? Thank you – malcolm the4 May 14 '13 at 22:21
In the buffer, how can I know that there is not something else to read ? – malcolm the4 May 14 '13 at 22:46
I have also tried the code from here : http://stackoverflow.com/questions/14576710/ping-application-in-android However I get nothing for ping. I can get results only for "ls" – malcolm the4 May 15 '13 at 00:14
If read() returns -1 the stream was closed and everything was transferred. Try to read until that happens. – Michael Butscher May 15 '13 at 09:21
I changed it to while(!((read=stdout.read(buffer))==-1)){ out += new String(buffer, 0, read); } but now the app freezes and does not show anything. I believe it stays stuck in the loop Any ideas ? – malcolm the4 May 15 '13 at 09:58

android shell commands getting the result

2 Answers2