How do I get the logfile from an Android device?

For those not interested in USB debugging or using adb there is an easier solution. In Android 6 (Not sure about prior version) there is an option under developer tools: Take Bug Report

Clicking this option will prepare a bug report and prompt you to save it to drive or have it sent in email.

I found this to be the easiest way to get logs. I don't like to turn on USB debugging.

I would use something of this sort :

$adb logcat -d > logcat.txt

The -d option dumps the entire circular buffer into the text file and if you are looking for a particular action/intent try

$adb logcat -d | grep 'com.whatever.you.are.looking.for' -B 100 -A 100 > shorterlog.txt

Hope this helps :)

Logcollector is a good option but you need to install it first.

When I want to get the logfile to send by mail, I usually do the following:

• connect the device to the pc.
• Check that I already setup my os for that particular device.
• Open a terminal
• Run adb shell logcat > log.txt

I hope this code will help someone. It took me 2 days to figure out how to log from device, and then filter it:

public File extractLogToFileAndWeb(){
        //set a file
        Date datum = new Date();
        SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd", Locale.ITALY);
        String fullName = df.format(datum)+"appLog.log";
        File file = new File (Environment.getExternalStorageDirectory(), fullName);

        //clears a file
        if(file.exists()){
            file.delete();
        }


        //write log to file
        int pid = android.os.Process.myPid();
        try {
            String command = String.format("logcat -d -v threadtime *:*");        
            Process process = Runtime.getRuntime().exec(command);

            BufferedReader reader = new BufferedReader(new InputStreamReader(process.getInputStream()));
            StringBuilder result = new StringBuilder();
            String currentLine = null;

            while ((currentLine = reader.readLine()) != null) {
                   if (currentLine != null && currentLine.contains(String.valueOf(pid))) {
                       result.append(currentLine);
                       result.append("\n");
                    }
            }

            FileWriter out = new FileWriter(file);
            out.write(result.toString());
            out.close();

            //Runtime.getRuntime().exec("logcat -d -v time -f "+file.getAbsolutePath());
        } catch (IOException e) {
            Toast.makeText(getApplicationContext(), e.toString(), Toast.LENGTH_SHORT).show();
        }


        //clear the log
        try {
            Runtime.getRuntime().exec("logcat -c");
        } catch (IOException e) {
            Toast.makeText(getApplicationContext(), e.toString(), Toast.LENGTH_SHORT).show();
        }

        return file;
    }

as pointed by @mehdok

add the permission to the manifest for reading logs

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