ADB (8)-View Log

The logs of the Android system are divided into two parts, and the underlying Linux kernel logs output to the/proc/kmsg,android log output to/dev/log.

Android logs

Command format:

[adb] logcat [

Common usage is listed below:

Filter logs by level

The logs for Android are divided into several levels:

• V--verbose (lowest, most output)
• D--debug
• I--info
• W--warning
• E--error
• F--fatal
• S--silent (highest, no output)

Filtering logs at a certain level will output logs of that level and above.

For example, command:

adb logcat *:W

The Warning, Error, Fatal, and Silent logs are output.

Filter logs by Tag and level

For example, command:

adb logcat ActivityManager:I MyApp:D *:S

Indicates the output tag ActivityManager of the above level of the log, output the MyApp Debug level of the tag log, and other tags of the Silent level log (that is, blocking other tag logs).

Log format

You can adb logcat -v  specify the log output format with options.

The logs are supported by the following types :

• Brief

  The default format. The format is:

  Example:

  D/HeadsetStateMachine( 1785): Disconnected process message: 10, size: 0

• Process

  The format is:

  Example:

  D( 1785) Disconnected process message: 10, size: 0  (HeadsetStateMachine)

• Tag

  The format is:

  Example:

  D/HeadsetStateMachine: Disconnected process message: 10, size: 0

• Raw

  The format is:

  Example:

  Disconnected process message: 10, size: 0

• Time

  The format is:

  Example:

  08-28 22:39:39.974 D/HeadsetStateMachine( 1785): Disconnected process message: 10, size: 0

• ThreadTime

  The format is:

  Example:

  08-28 22:39:39.974  1785  1832 D HeadsetStateMachine: Disconnected process message: 10, size: 0

• Long

  The format is:

  [  : / ]

  Example:

  [ 08-28 22:39:39.974  1785: 1832 D/HeadsetStateMachine ]Disconnected process message: 10, size: 0

The specified format can be used in conjunction with the above filtering. Like what:

adb logcat -v long ActivityManager:I *:S

Empty log

adb logcat -c

Kernel log

Command:

adb shell dmesg

Output Example:

<6>[14201.684016] PM: noirq resume of devices complete after 0.982 msecs<6>[14201.685525] PM: early resume of devices complete after 0.838 msecs<6>[14201.753642] PM: resume of devices complete after 68.106 msecs<4>[14201.755954] Restarting tasks ... done.<6>[14201.771229] PM: suspend exit 2016-08-28 13:31:32.679217193 UTC<6>[14201.872373] PM: suspend entry 2016-08-28 13:31:32.780363596 UTC<6>[14201.872498] PM: Syncing filesystems ... done.

In parentheses, the [14201.684016] time, in seconds, after the kernel starts to start.

Through the kernel log we can do something, such as measuring the kernel boot time, in the kernel log after the system started to find the Freeing init memory line in front of the time is.

ADB (8)-View Log