Read the device log

Watch a device's log as it arrives, narrow it down to the lines you care about, and save them to a file.

What logcat is

Android keeps a running log of messages from the system and from every app. The tool that reads it is called logcat. When an app crashes or misbehaves, the reason is usually in this log.

Each line has a time, the process and thread that wrote it, a priority, a tag naming the part of the code that wrote it, and the message.

The six priorities, from least to most serious:

Letter	Priority	Colour in DroidDeck
V	Verbose	Grey
D	Debug	Blue
I	Info	Green
W	Warning	Orange
E	Error	Red
F	Fatal	Purple

Error and Fatal lines also get a tinted background so they stand out.

The Logcat toolbar

1. 1Pause view — Freezes the list so you can read it. The button becomes Resume.
2. 2Clear — Empties the list and erases the log stored on the device.
3. 3Export — Saves the lines you can see to a file in Downloads.
4. 4Priority — Shows lines of the chosen priority and anything more serious.
5. 5Tag — Shows lines whose tag contains this text.
6. 6Contains — Shows lines whose message contains this text.
7. 7Package — Shows lines written by one app, given its package name.
8. 8Counter — Lines shown, then lines held in memory.

The log starts by itself when a device is selected. New lines appear at the bottom.

Filter the log

Filters combine: a line must pass every filter you set. Filters apply to lines already in the list as well as new ones, so you can change them freely without losing anything.

By priority

Select a letter in V D I W E F. The view shows that priority and every more serious one. W shows warnings, errors and fatal lines. V shows everything.

By tag

Type part of a tag in Tag. Matching ignores upper and lower case, and the text can be anywhere in the tag: activity matches ActivityManager.

By message text

Type in Contains to keep lines whose message includes that text, ignoring case.

By app

Type an app's full package name in Package, for example com.example.myapp. The name must be exact.

DroidDeck looks up the app's process and shows only lines from it. A chip next to the field tells you what it found:

• pid and a number: the app is running, and you are seeing its lines.
• not running: no process has that name, so the view is empty.

DroidDeck checks again every three seconds. When you restart the app and it gets a new process, the filter follows it.

TIP

The package name is listed on the Apps tab. Search for the app there and read its name from the list.

Read a long line

Lines are cut to fit one row. Select a line to open it in full in a small window, where you can select and copy the text. Select Close when you are done.

Pause and scroll

• Select Pause view to freeze the list. The log keeps being collected in the background. Select Resume to show what arrived meanwhile.
• Scroll up to read older lines. A round Jump to latest button appears at the bottom right; select it to return to the newest line.

Clear the log

Select Clear (logcat -c), the bin icon with lines.

WARNING

Clear does two things: it empties DroidDeck's list, and it erases the log buffer on the device itself. Lines from before that moment are gone and cannot be read again by DroidDeck or any other tool. Export first if you might need them.

Export the log

Select Export current view to ~/Downloads, the download icon.

DroidDeck writes the lines that pass your filters to a text file in your Downloads folder, named droiddeck-logcat-, the device's serial, and the date and time, ending in .log. A message at the bottom of the window shows the full path.

Only what the filters show is exported. To export everything, set the priority to V and empty the three filter fields first.

How much log is kept

DroidDeck holds the most recent 50,000 lines in memory. The counter on the toolbar reads, for example, 585 / 585: lines shown by your filters, then lines held. When it adds (ring full), the limit has been reached and the oldest lines are dropped as new ones arrive.

Switching to another device in the device picker starts an empty log for that device.

If the log stops

If the stream ends, for example because the device disconnected for a moment, a red message such as logcat exited (code 1) appears under the toolbar, and a Restart stream button joins the toolbar. Select it to start reading again.

Next steps

• Manage apps: find package names, install a build.
• Use the shell and quick actions
• Reference: file names and locations.