Write android logcat data to a file

Question

I want to dump Android logcat in a file whenever user wants to collect logs. Through adb tools we can redirect logs to a file using adb logcat -f filename, but how can I do this programmatically?

http://stackoverflow.com/a/8417757/1012284 – Padma Kumar Jul 03 '12 at 09:22 — Padma Kumar, Jul 03 '12 at 09:22

score 126 · Accepted Answer · edited Sep 10 '16 at 09:34

126

Here is an example of reading the logs.

You could change this to write to a file instead of to a TextView.

Need permission in AndroidManifest:

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

Code:

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) {
    }
  }
}

edited Sep 10 '16 at 09:34

Shashanth

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answered May 30 '11 at 10:53

jkhouw1

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@jkhouw1... +60 Best answer i ever seen and great way to post an answer, (also i learn from you) This answer will be always helpful even link got dead,all i need to add just Scroll View and i have done what i wanted, because of your answer, Cheers!! – swiftBoy Jul 03 '12 at 05:58
Great..But is there a way to filter these logs as per the Tags? – AbhishekB Aug 28 '12 at 10:55
1

i haven't tested this but i think you would change it to "logcat -d -s YourTagToFilterOn" – jkhouw1 Aug 28 '12 at 11:28
How can we put the package name filter. – kamal_tech_view Mar 12 '14 at 06:38
4

This permission was removed in Android 4.3, so apps can no longer use it beyond their process. Also, many devices have taken it a step further and this outputs nothing. I don't have a list because I see it fairly often. – Tom Sep 19 '14 at 20:32
@Tom: Do we have any other way to get logs and save theme in a file. My app have a option to report problem, where i want to upload that file to server. – Max Jun 05 '15 at 10:26
logcat command line options are described here https://developer.android.com/studio/command-line/logcat.html – jayeffkay Dec 07 '16 at 10:22
Very nice! This is exactly what I am looking for. I changed it slightly to dump the log output to a file whenever my application crashes. – Shadoninja Apr 07 '17 at 04:34
@Shadoninja hi, how you know your app crashes? where you add this code? – flankechen Aug 19 '20 at 09:25
@flankechen - I don't remember exactly how I did it, but I have some ideas for you. One way you could do this is to have your `main` function execute the rest of your program in a try/catch block and `catch` the generic `Exception` class. When you do this, any time your program crashes, you could output the exception to logcat. – Shadoninja Aug 23 '20 at 15:14

score 43 · Answer 2 · answered Nov 14 '12 at 23:30

43

Logcat can write directly to a file:

public static void saveLogcatToFile(Context context) {    
    String fileName = "logcat_"+System.currentTimeMillis()+".txt";
    File outputFile = new File(context.getExternalCacheDir(),fileName);
    @SuppressWarnings("unused")
    Process process = Runtime.getRuntime().exec("logcat -f "+outputFile.getAbsolutePath());
}

more info on logcat: see http://developer.android.com/tools/debugging/debugging-log.html

answered Nov 14 '12 at 23:30

Stéphane

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This command seems to stall since logcat -f doesn't automatically exit. Any way to write the log to a file and automatically exit the process similar to logcat -d ? – Phillip Jan 08 '14 at 06:39
Try to put an & to the end make it background. – ShihabSoft Jun 01 '15 at 10:49
7

logcat -df sink all logs to the and exits immediately. – Alexander Skvortsov Feb 26 '16 at 10:24
After initially using this approach, I switched to using a buffered reader and writer because -f doesn't handle spaces in file names well. – LordParsley Jun 22 '16 at 09:27
Yes, it should be -df. Also **Note: This code dumps it in external cache directory** – Atul Jul 27 '16 at 18:01

score 1 · Answer 3 · edited Oct 17 '19 at 07:57

Or you can try this variant

try {
    final File path = new File(
            Environment.getExternalStorageDirectory(), "DBO_logs5");
    if (!path.exists()) {
        path.mkdir();
    }
    Runtime.getRuntime().exec(
            "logcat  -d -f " + path + File.separator
                    + "dbo_logcat"
                    + ".txt");
} catch (IOException e) {
    e.printStackTrace();
}

score 0 · Answer 4 · answered Jul 10 '17 at 06:26

public static void writeLogToFile(Context context) {    
    String fileName = "logcat.txt";
    File file= new File(context.getExternalCacheDir(),fileName);
    if(!file.exists())
         file.createNewFile();
    String command = "logcat -f "+file.getAbsolutePath();
    Runtime.getRuntime().exec(command);
}

Above method will write all logs into the file. Also please add below permissions in Manifest file

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

Write android logcat data to a file

4 Answers4

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