Develop Reference

System.out.print with // prints the code Blue. What is the meaning of this?

System.out.println(TAG + " //METHOD_STARTED// - //start_firebase_and_get_userID//");
Why if I write these in my app, it comes in blue in the console after the //?

It appears to be mistaking it for a hyperlink.
//METHOD_STARTED// is a valid protocol-relative URL (domain names don't have to have dots if they're on your local network), and it seems that Android Studio/IntelliJ's link detection is falling for it. Of course, it's not valid in this case, because there's no protocol in the log output for it to be relative to, so really this is a bug.

What is the purpose of using double underscore ( __ ) before the start and after the end of an file name in c?

I'm studying the android kernel as a beginner. I can read the messages thrown from the macro ERROR() inside the function main() at system/core/init/init.c using dmesg command through adb. I observed that after calling the function open_devnull_stdio() inside main(), dmesg no longer displays the messages thrown by ERROR().
To find the reason, I started digging into the declaration of open_devnull_stdio() inside system/core/init/util.c and I found this line I can't understand
static const char *name = "/dev/__null__";
Actually there was no file named __null__ inside /dev/ in the device, but there was a file named null and I was able to grab it using adb pull and it was a 0 byte (empty) file.
So why is a file name wrapped with double underscore (__) ?
Here is the link for the util.c

There is no special purpose of using double underscore before the start, after the end or both in C. From the point of view of C the file name is just a string, the operating system is free to interpret in whatever way it chooses. From the point of view of Linux, the same applies. Underscores in file names are just characters. They are not treated differently from the letters b and t.
If I guessed right and I'm reading the same file as you (it might be a good idea to link to the source code you're reading) then it should be pretty obvious what the code does on the lines after the one you mentioned. The next lines are:
if (mknod(name, S_IFCHR | 0600, (1 << 8) | 3) == 0) {
fd = open(name, O_RDWR);
unlink(name);
Which creates the null device which is then opened and immediately deleted again.
I suspect this is done so that programs can run without access to the root filesystem and still be able to open the equivalent of /dev/null.

I don't know the answer but I have an idea:
The following page shows an "strace" output where /dev/__null__ is used:
https://gist.github.com/tetsu-koba/1522515
Under Linux device files have a 33-bit (?) number which identifies the device. (At least under old Linux versions) you could delete some file in /dev and you could restore it or even create it in another directory (!) when you know the 33-bit number! (So you can delete the device /dev/sda2 and create the device (not file!) /home/myuser/sda2 instead.)
The trace in the link above shows the following three lines:
mknod("/dev/__null__", S_IFCHR|0600, makedev(1, 3)) = 0
open("/dev/__null__", O_RDWR|O_LARGEFILE) = 3
unlink("/dev/__null__") = 0
These lines will create the device file /dev/__null__ (with the 33-bit number identifying /dev/null). Then it opens that file and then it removes the file again.
Maybe this is done because the tool shall be able to run both on Linux installations where the device file "/dev/null" is present (in this case the file should not be overwritten) and on installations where that file is missing (in this case a replacement file must be created using the known 33-bit number).

As other people have pointed out this just tells it's the "null device", not a regular file called "null". null is supposed to act like an information sink, not like a normal file where you dump your data to. Hope this helps.

Titanium SDK 5.4.0.GA is showing too many logs at console on Android platform

did anyone notice that on Android - Ti SDK 5.4.0.GA is showing many output at console on all modes like Trace, Debug, Info, Warning, Error.
I have not tried it for Wi-Fi off state, but it is showing such lines every second when the device is connected to Wi-Fi and my console filled up with 100 lines in just few seconds:
[INFO] : D/StatusBar.MSimNetworkController( 1166): getNumberOfActiveSim:0
[INFO] : D/StatusBar.MSimNetworkController( 1166): getPhoneSignalIconList: mMaxLevelOfSignalStrengthIndicator = 4 inetCondition = 0
[INFO] : D/StatusBar.MSimNetworkController( 1166): getDataSignalIconId: mMaxLevelOfSignalStrengthIndicator = 4 inetCondition = 0 iconLevel = 4
[INFO] : D/StatusBar.MSimNetworkController( 1166): updateTelephonySignalStrength: iconLevel=4
Can anyone suggest any solution as this is getting quite annoying and I cannot focus on the console output from code due to too many above logs?

Update
Finally I found a solution to this problem:
https://github.com/appcelerator/titanium_mobile/pull/8754
Logs that contain a dot (or any other character besides letters) won't be caught in the don't show part!
The PR will change the RegEx rule to match any character.
Old solution:
Check the output of ti config cli.logLevel and set it to info
Might solve the problem for you.
I'm facing the same issue and I use monitor with this custom filter:
^(?!(WifiStateMachine|WIFI_UT|AppOps|GraphicsStats|RegisteredNfcid2Cache|Wifi|NotifUtils|WIFI|usbnet|Ethernet|FaceDetectTask|RecentsTaskLoadPlan|MorningBundlePlugin|SocialManagerService|PhoneApp|LoadDialerReceiver|Icing|Herrevad|Finsky|StatusBarManagerService|DropBoxEntryAddedChimeraService|ClearcutLoggerApiImpl|AlarmManager|GCoreUlr|GCoreFlp|APSAnalyticsService|QCNEJ|NetworkStats|IpReachabilityMonitor|Nfcid2RoutingManager|ls|WifiManager|libc|dex2oat|ACRA|HtcMirrorLinkAmsListener|LOWI-Scan|DownloadManagerWrapper|wpa_supplicant|QCALOG|WIFI_ICON|HtcWrapCustomizationManager|gdlights|PowerUtils|ExtremePowerSave|WifiService|FrameworkListener|MediaRouterServie|DotMatrix|PowerUI|PMS|XTCC-5.1.0.7|NetworkManagement|HtcPowerSaver|BatteryControlle|NetLinkSocketObs|WifiController|NetlinkSocketObs|BatteryService|UsbnetService|DeviceIdleControler|Keyboard.Facilit|xiaomi|qdlights|SensorService|AutoSetting|HtcWifiRssiMonitor|HtcWifiDataStallTracker|WifiAutoJoinController|HtcWLD_v5.1.0|WifiMonitor|WifiConfigStore|StatusBar.NetworkController|CwMcuSensor|BrcmNfcJni|DATA_ICON|TelephoneCallback|ContactMessageStore|HtcUPManager|ScreenOnOffReceiver|DeviceIdleController|QSPanel|NetworkPolicy|GpsLocationProvider|SensorManager|SmartNS_PSService|PhoneStatusBar|ScrimController|Settings|LocationManagerService|getVisibilityByRssi|NetworkController.WifiSignalController|GAv4|IntegrityChecker|KernelCpuSpeedReader|KernelWakelockReader|BatteryStatsImpl|WeatherUtility|WeatherTimeKeeper|PNP_UPDATERD|DsService|PathParser|StatusBarManagerServiceHtcASN_1.1|SignalClusterView|SIGNAL_ICON|HtcSystemUPManager|ConnectivityService|HtcASN_1.1|SignalClusterView|SIGNAL_ICON|HtcSystemUPManager|ConnectivityService|WSP|Babel|CityCodeHelper|TetherStatsReporting|TelephonyCallback))
Put this in by Log Tag in a new filter. My device is a HTC A9, a very log-noisy device!
If you still see rows you don't want to just put attach the tags with |tagname

LogCat Android - how to get filename with the error

I have this problem:
I start a java application as "Android application" in Eclipse Juno.
So the virtual device starts and the log messages begin to scroll in the LogCat tab.
The columns of the tab are Level, Time, PID, TID, Application, Tag, Text.
Is there a way to see the filename where an error message comes from ?
For example I get the text: "sqlite returned: error code 14, msg=cannot open file at source line 25467" and the tag is "Database".
So how could I know in which file this error has been generated ?
Thanx
A

You can double click in the red lines and they jump to the code source which gives the error

You can use filename as a tag while logging. E.g Log.i("YourFileName", "Your Log");

Somewhere it usually says "caused by" and then it lists files and lines where the exception happened

I systematically add a
static final String TAG = "ClassName";
property to all classes definitions and use it on
Log.x(TAG, "Whatever");

Android display OpenCore logs

I am trying to display opencore logs. I have already tried the ff. but still logs are not showing in the logcat.
1. created pvlogger.txt in sdcard and still no use.
# echo 8 > /sdcard/pvlogger.txt
2. Edited the PV_LOG_INST_LEVEL from 0 to 5 in the pvlogger.h file but it causes the compilation to fail.
"/android_log_appender.h:75: error:" format not a string literal and no format argument"
So I have just commented out Line 75, although it compiled successfully, opencore logs are still not showing in the logcat.
Is there anyone who were able to display the opencore logs?
Thanks in advance.
artsylar

I had this issue three months ago. Please don't comment out LOGE(stringbuf) in /android_log_appender.h, otherwise there is no log out.
LOGE("%s", stringbuf) instead of LOGE(stringbuf).
1. created pvlogger.txt in sdcard and still no use.
`# echo 8 > /sdcard/pvlogger.txt`
2. Edited the PV_LOG_INST_LEVEL from 0 to 5 in the pvlogger.h.
3. ENABLE_PV_LOGGING from 0 to 1 in the pvlogger.h.
4. LOGE("%s", stringbuf) instead of LOGE(stringbuf) in /android_log_appender.h.
Wish you success!

After trial and errors, I was finally able to show the OpenCore log messages! Here's what I did although I do not know yet if steps 4 and make options are needed.
Added #define PV_LOG_INST_LEVEL 5 to \android\external\opencore\android\thread_init.cpp file.
To solve the "/android_log_appender.h:75: error:" format not a string literal and no format argument" error, just edit \external\opencore\android\android_log_appender.h line 75 from LOGE(stringbuf) to LOGE("%s", stringbuf)
compile the code.
make ENABLE_PV_LOGGING=1
create pvlogger.txt in sdcard.
# echo 8 > /sdcard/pvlogger.txt