Catch LogCat programmatically or export it to file?

try {
   File filename = new File(Environment.getExternalStorageDirectory()+"/gphoto4.html"); 
        filename.createNewFile(); 
        String cmd = "logcat -d -f "+filename.getAbsolutePath();
        Runtime.getRuntime().exec(cmd);
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

also use

String cmd = "logcat -v time -r 100 -f <filename> [TAG]:I [MyApp]:D *:S";
Runtime.getRuntime().exec(cmd);


-v -> Sets the output format for log messages.
-r -> for specifying the size of file.
-f -> file to which you want to write the logs.
[TAG] -> Tag of your application's log.
[MyApp] -> Your application name.

File filename = new File(Environment.getExternalStorageDirectory()+"/mylog.log"); 
filename.createNewFile(); 
String cmd = "logcat -d -f"+filename.getAbsolutePath();
Runtime.getRuntime().exec(cmd);

it works for me. but for all logcat output not for special tag(mytag).

public class LogTest extends Activity {
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
try {
  Process process = Runtime.getRuntime().exec("logcat -d");
  BufferedReader bufferedReader = new BufferedReader(
  new InputStreamReader(process.getInputStream()));

  StringBuilder log=new StringBuilder();
  String line;
  while ((line = bufferedReader.readLine()) != null) {
    log.append(line);
  }
  TextView tv = (TextView)findViewById(R.id.textView1);
  tv.setText(log.toString());
} catch (IOException e) {
}
}
}

also you need

<uses-permission android:name="android.permission.READ_LOGS" />

referenced here