1. JHutson456's Avatar
    adb logcat bootcamp

    I'm going to be teaching the basics of logcats. I sat for a few hours a while back and hammered all this stuff out with ckisgen from XDA/ACS holding my hand the whole way, so this is good info here. I did the whole thing in Ubuntu (Linux) and have listed the Window$ $pecific desktop pathing below the Linux command. UNIVERSAL COMMANDS LINUX COMMANDS WINDOWS COMMANDS.

    When I say Terminal, I mean Command Prompt for you Window$ u$er$ (start-run-cmd)

    In terminal with your phone plugged into the computer

    A Logcat:

    adb logcat
    This doesn't START logcat, this tells terminal to grab the information already on the device logcat and display it in terminal. This isn't so useful to us. It just scrolls the information in terminal and you can read it there. This is kinda difficult to read though, for one it's constantly scrolling as your phone does things and two, it's likely that your terminal is configured to only allow a certain number of lines to be kept readable before they drop off.

    Pipe it to Desktop as a .txt file

    adb logcat > ~/Desktop/logcat.txt 
    adb logcat > %userprofile%\desktop\logcat.txt

    This command above will tell the logcat to export the terminal logcat to a .txt file on your desktop called logcat.txt The '>' symbol tells the logcat to pipe to the location listed. This will continue to update even if you open the text file, so long as you have terminal running. It's not done live though, you have to either refresh the file, or close it then re-open it. That won't affect anything other than giving you an update. Now we're getting somewhere, but where?

    adb logcat > /sdcard/logcat.txt

    If using Terminal Emulator on your phone instead of a computer setup, this (above) is the code you'd want to use. It will save the logcat.txt to the root of your SD card. Next!

    -v long, or not to -v long, that is the question!

    adb logcat -v long > ~/Desktop/logcat.txt
    adb logcat -v long > %userprofile%\desktop\logcat.txt

    Now we're telling the logcat to do something more interesting. We are telling it to give us every scrap of information it has. This will space the logcat out nice and pretty and really make things easier to read as well, even giving time stamps of when everything happened! Now you can say it happened at about 9:30 pm and we can find that. Winning!
    Sometimes you want to filter down the information though. You want to make the dev's life easier. Here is how:

    First, a brief on Tags and Priorities.

    Tags are going to be what process is actually giving the information, for example 'ActivityManager', 'Database', and 'WindowsManager' are all Tags you can find. There are TONS of these suckers! Research into what your problem is and try to pick out the tag.

    Priorities are different. These will tell you how serious the issue at hand is. The priorities are called by their letter code and are:

    V Verbose
    D Debug
    I Info
    W Warning
    E Error
    F Fatal

    S Silent (suppress all output)

    These are in ascending order. In other words, Verbose or V is going to be the micro information which doesn't really mean much to anyone 99.99% of the time where as Fatal or F is going to be a huge catastrophic issue. When filtering for a Priority it will include the Priority you give PLUS all HIGHER Priorities. So, for example, if you call to filter for Warning or W then it will give you Warning, Error, and Fatal. That is common to filter for. Below are some examples of code:

    ( PS - you would never actually type or input { or } in your logcat commands .. they are in some of the examples below to show you that these are generic modifiers meaning - if you were actually inputting the command you would replace the {Tag} with an actual Tag, like: ActivityManager or GTalkService .. in the same way you would replace {Priority} with an actual Priority, such as: W or E )


    adb logcat {Tag}:{Priority} *:S > ~/Desktop/logcat.txt
    adb logcat {Tag}:{Priority} *:S > %userprofile%\desktop\logcat.txt

    The above line is if you know exactly what Tag (GTalkService or ActivityManager) and Priority (W or E) you are looking for.

    adb logcat *:{Priority} *:S > ~/Desktop/logcat.txt
    adb logcat *:{Priority} *:S > %userprofile%\desktop\logcat.txt

    The above line is if you don't know the Tag, but know the Priority. The * is a wild card that basically means all/any. An example of a VERY valuable logcat could be:

    adb logcat *:W *:S > ~/Desktop/logcatALLwarnings.txt
    adb logcat *:W *:S > %userprofile%\desktop\logcat.txt

    So, the command above would give you all tags that had a priority of Warning, Error, or Fatal. It would silence (not show) everything else and would pipe the output of your log to your desktop as a text file named logcatALLwarnings.txt moving along

    adb logcat {Tag}:V *:S > ~/Desktop/logcat.txt
    adb logcat {Tag}:V *:S > %userprofile%\desktop\logcat.txt

    The above line is if you know the Tag but want to see all Priorities. {Tag}:V outputs all priorities for the specific Tag youve entered because it calls for the V (Verbose) priority, which is the very lowest priority and as you recall, it always gives you the priority youve asked for AND above.

    The *:S tells the logcat to Silence (or ignore) all lines/messages that have not otherwise been specifically called for using these filter expressions. This CAN cause issues though, sometimes it will silence what you're looking for / everything.

    A final specific example from my phone to be clear. I got a Database Tag with an Info Priority, if I wanted to see all instances of this happening, I could use the following code:

    adb logcat Database:I *:S > ~/Desktop/logcat.txt
    adb logcat Database:I *:S > %userprofile%\desktop\logcat.txt

    Or, if I had an ActivityManager Warning I could use

    adb logcat ActivityManager:W *:S > ~/Desktop/logcat.txt
    adb logcat ActivityManager:W *:S > %userprofile%\desktop\logcat.txt

    Ok, now we're going to the show! You know the tools, but how do I use them? Glad you asked!

    For the first time you boot a ROM/Kernel bundled together (IE InsomMIUI 1.12.2) or for just a kernel you're going to do the following:

    Once you're finished full wiping and installing the ROM, but haven't rebooted the phone yet. (Or wiping just the caches for a separate Kernel):

    • Open Terminal on your computer
    • enter the following code

    adb logcat -v long > ~/Desktop/logcat.txt
    adb logcat -v long > %userprofile%\desktop\logcat.txt

    • Name the logcat something useful. A good format is to use you're initials, rom name, what it is, and date. This way it stands out. So the code with the really long but helpful file name would be:

    adb logcat -v long > ~/Desktop/JH_InsomMIUI1122_firstboot_5Dect11.txt
    adb logcat -v long > %userprofile%\desktop\JH_InsomMIUI1122_firstboot_5Dect11.txt

    • Yes, I know that's a long name, but we look at dozens of these things, it helps!
      • In recovery tell it to reboot the phone. The logcat will start recording internally on your device at boot automatically.
      • Once the phone is at the lockscreen let it sit for 5 minutes.
      • Unlock the phone and let it sit for about 10 seconds.
      • Restart the phone.
      • Once you restart the phone open the logcat file on your desktop to make sure its not blank/empty/something went wrong and if everythings golden - send to your favorite developer (ME! ).

    • FYI , the -v option sets the output format. -v long after the logcat command formats the log so that it adds a date and time stamp to each line. It also separates each line with a blank line .. making the log as a whole much easier to look through.

    • That's it, you should be off to the races with these logcats. I hope this has helped!
    12-15-2011 05:26 AM
  2. chrstdvd's Avatar
    I read this thread and started thinking that I had seen one of these text files somewhere on my computer. I think it is this one because you can click the arrow where it now says Verbose and have the other choices you have instructed about in the post. I will have to study your instructions and see if I can do a script to mimic what this screen shot is showing. Thanks

    Attachment 18964

    See where it says "fail port mapping". That means I can not connect my phone over 3G/4G to this computer. I have the same problem with the Plex application, but they must use really verbose logs because I can not read them well. Now that I know this, I will tinker with the Plex application and see if I can make a script to make a log a little more understandable.

    I know the reason now why port mapping fails; it is because I use Hughes Net as my ISP and they block all ports unless you purchase a static IP address for your system. I got around the problem by using Audio Galaxy which works similar to a cloud server but does not upload my media to the cloud, like say Google Music would.
    12-15-2011 06:42 AM
  3. srkmagnus's Avatar
    Is there any personal data from the logcat created? I've always Wondered anything could be sent that I don't want floating around in a logcat.
    12-18-2011 05:47 PM
  4. JHutson456's Avatar
    Is there any personal data from the logcat created? I've always Wondered anything could be sent that I don't want floating around in a logcat.
    I can tell a lot but I don't recall ever seeing anything like a text message print or the like. Let me play around and see.

    this has been a message from the dead pool.
    12-19-2011 02:56 AM
  5. srkmagnus's Avatar
    Thanks :-). I understood the value a logcat gasvto developers but always wondered about this.

    Sent from my HERO200 using Tapatalk
    12-19-2011 11:05 AM
  6. Jsmokey's Avatar
    Great little guide Jhutson. I completely understood reading logcats prior to this but a few of the extra command options I hadn't bothered with before so it was a nice little refresher on a a few points to me and definitely a must for anyone aspiring to do any sort of mods to android especially with all the posts I've came across in the past asking for explanations on how to read logcats which really should be everyones first step to modding aside from learning the file types, what they do and which one's are absolutely necessary for android to run without any fc's, bootloops, etc...
    12-21-2011 12:13 AM
  7. ksg97's Avatar
    Thanks your commands really helped this noob, but couldn't use them until I downloaded the sdk tool kit form another site will post another comment with a link for a good video to help anyone else who stops by here.
    01-21-2013 02:47 PM
  8. evdsande's Avatar
    To view the logcat output in Eclipse or AndroidStudio is sometimes a real hassle because of the huge number of logmessages passing by and when you filter in logcat you loose the filtered messages and cannot recall the these anymore. What I use is logcatUDP.apk and TailExpert. With logcatUDP you sent all logcat messages to TailExpert via wifi and in TailExpert you can filter the messages you don’t want to see. For logcatUDP you need a rooted phone but you can also use adb to write your logcat messages to a file and watch this file with TailExpert. Both TailExpert and logcatUDP are free for private use and you can download both logcatUDP and TailExpert see tailexpert.neware.nl
    07-20-2015 06:01 AM
  9. evdsande's Avatar
    07-20-2015 06:02 AM
  10. Wolfling36's Avatar
    Don't know if anyone looks at this anymore...
    But, I haven't used a terminal in a while. Tell me like I'm a child... what state does my phone have to be in? I have an LG G3. Put it in recovery? normal UI? Bootloader?
    06-20-2016 04:06 PM
  11. PackElend's Avatar
    @JHutson456 that's the best tutorial about logcat I've found so far and I've searching a lot for comprehensive tutorial.

    I've always wondered myself how and in particular when log entries are done. You said
    This doesn't START logcat, this tells terminal to grab the information already on the device logcat and display it in terminal.
    Can you say more about it?

    I'm quiet a noob in regard to logcat. I got it to work and my logs seem to be usable but I don't really know what I did.
    Based on endless reading and trying I figured out that that I can retrieve logs as soon as logcat viewer is connected to my phone. There are multiple viewers on available as discussed on stackoverflow -> android desktop log viewer or do it only by the means of ADB.

    Furthermore I found good explanation about the log levels xda developers->guide sending a logcat to help debug your favorite app what is as good as yours.
    stackoverflow -> android log main events radio buffers explains well the message types (what you may can add?).
    But what do you do when you on the move with phone. I know there a plenty of apps.

    mLogcat allowed me to save huge logs what began before I connected it to a desktop PC. It seems that MatLog can access historical logs as well.

    I cannot explain how that is possible sine any other viewer shows only live logs and may shows only a limited number of log entries.
    So I would like to know how is the logging process started and how it is ended. Is there any command or does an logcat app need to run. If an app is necessary, does it have to run in the foreground or background?

    There are the options Logger buffer sizes and Store logger data persistently on device. in Developer options (of at least LineageOS) that may have an impact on put my knowledge is to limited to say it.
    10-19-2017 06:37 AM