The Android logging system provides a mechanism for collecting and viewing system debug
output. Logs from various applications and portions of the system are collected in a series of
circular buffers, which then can be viewed and filtered by the logcat command. You can use
logcat from an ADB shell to view the log messages.
For complete information about logcat options and filtering specifications, see Reading and Writing Logs.
For more information on accessing logcat from DDMS, instead of the command line, see
Using DDMS.
Syntax
[adb] logcat [<option>] ... [<filter-spec>] ...
You can run logcat as an adb command or directly in a shell prompt
of your emulator or connected device. To view log output using adb, navigate to your SDK
platform-tools/ directory and execute:
$ adb logcat
You can create a shell connection to a device and execute:
$ adb shell # logcat
Options
The following table describes the command line options of logcat.
| Option | Description |
|---|---|
-b <buffer> |
Loads an alternate log buffer for viewing, such as events or
radio. The main buffer is used by default. See Viewing Alternative Log Buffers. |
-c |
Clears (flushes) the entire log and exits. |
-d |
Dumps the log to the screen and exits. |
-f <filename> |
Writes log message output to <filename>. The default is
stdout. |
-g |
Prints the size of the specified log buffer and exits. |
-n <count> |
Sets the maximum number of rotated logs to <count>. The default value
is 4. Requires the -r option. |
-r <kbytes> |
Rotates the log file every <kbytes> of output. The default value is
16. Requires the -f option. |
-s |
Sets the default filter spec to silent. |
-v <format> |
Sets the output format for log messages. The default is brief format. For a
list of supported formats, see Controlling Log Output
Format. |