Question

I have a single android device attached to the pc and have opened multiple shells which show logcat information. Everyone running with its specific filter.
So my question is now, where are those filters applied? Already on the phone so only the filtered messages are sent over usb. Or are they applied on the pc on the adb server or client? I just want to prevent having multiple unfiltered logcat streams running simultaneous over the usb since I have limited bandwitdh.
Thanks

Answer 1

The data is pulled out of kernel buffers with the logcat command on the device. If you run

% adb logcat -\?

you can see the usage info, which includes a description of “filterspecs”. These can be set on the command line, or by setting the ANDROID_LOG_TAGS. For example:

% adb logcat '*:W'

will show you only messages at Warning or Error level.

The trick here is that adb logcat is just shorthand for adb shell logcat, with the added bonus of propagating your ANDROID_LOG_TAGS environment variable to the device. The filtering is being done by the logcat command, which is just dumping text output over adb. The output from the logcat command doesn’t get any special treatment.

So the answer to your question is: the filtering happens on the device, individually for each window.

DDMS works differently.