How to read the output of jsch command in Android?

Question

I'm building an android app using JSCH library to execute a command in a remote linux server, and then read its output.

I followed the answer of this question, but didn't solve my problem.

The following is my activity code:

package com.example.pic_controller_2;

        import android.graphics.drawable.Drawable;
        import android.support.v7.app.AppCompatActivity;
        import android.os.Bundle;
        import android.app.Activity;
        import java.io.BufferedInputStream;
        import java.io.BufferedOutputStream;
        import java.io.ByteArrayOutputStream;
        import java.io.File;
        import java.io.FileOutputStream;
        import java.io.OutputStream;
        import com.jcraft.jsch.Channel;
        import com.jcraft.jsch.ChannelExec;
        import com.jcraft.jsch.JSch;
        import com.jcraft.jsch.JSchException;
        import com.jcraft.jsch.Session;
        import com.jcraft.jsch.ChannelSftp;
        import android.view.View;
        import android.os.AsyncTask;
        import android.widget.Button;
        import android.widget.ImageView;
        import android.widget.Toast;

public class TestActivity extends AppCompatActivity {

    private String aaaa;

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_test);
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);
    }

    public void show_picture_func (View v) {   

        new AsyncTask<Integer, Void, Void>(){    

            @Override
            protected Void doInBackground(Integer... params) {

                String SFTPHOST = "192.168.0.1";
                int SFTPPORT = 22;
                String SFTPUSER = "pi";
                String SFTPPASS = "raspberry";
                String SFTPWORKINGDIR = "/home/pi/pic/";

                Session session = null;
                Channel channel = null;
                ChannelSftp channelSftp = null;

                try {
                    JSch jsch = new JSch();
                    session = jsch.getSession(SFTPUSER, SFTPHOST, SFTPPORT);
                    session.setPassword(SFTPPASS);
                    session.setConfig("StrictHostKeyChecking", "no");
                    session.setTimeout(10000);
                    session.connect();

                    ChannelExec channel1 = (ChannelExec)session.openChannel("exec");
                    final ByteArrayOutputStream baos = new ByteArrayOutputStream();
                    channel1.setOutputStream(baos);
                    channel1.setCommand("ls /home/pi/pic | sed -n 5p");
                    aaaa = new String(baos.toByteArray());

                } catch (Exception ex) {
                    ex.printStackTrace();
                    Toast.makeText(getApplicationContext(), "Error Connecting", Toast.LENGTH_LONG).show();
                }
                return null;
            }


            @Override
            protected void onPostExecute(Void unused) {
                TextView textView1_2 = (TextView)findViewById(R.id.textView1);
                textView1_2.setText(aaaa);
            }


        }.execute(1);

    }

}

So, the output of the executed command should appear in the textview. But it doesn't. The textview changes to white!

Any suggestions !?

Answer 1

I changed the following section of the code, from this:

ChannelExec channel1 = (ChannelExec)session.openChannel("exec");
final ByteArrayOutputStream baos = new ByteArrayOutputStream();
channel1.setOutputStream(baos);
channel1.setCommand("ls /home/pi/pic | sed -n 5p");
aaaa = new String(baos.toByteArray());

to this:

ChannelExec channel1 = (ChannelExec)session.openChannel("exec");
final ByteArrayOutputStream baos = new ByteArrayOutputStream();
channel1.setOutputStream(baos);
channel1.setCommand("ls /home/pi/pic | sed -n 5p | xargs echo -n");
channel1.connect();
try{Thread.sleep(1000);}catch(Exception ee){}
aaaa = new String(baos.toByteArray());

And the problem solved.