关键词：logcat; radio; system; events; logcat -b system -b main -b radio -b events
logcat -b 的作用如下：
-b <buffer>, --buffer=<buffer> Request alternate ring buffer, 'main', 'system', 'radio', 'events', 'crash', 'default' or 'all'. Multiple -b parameters or comma separated list of buffers are allowed. Buffers interleaved. Default -b main,system,crash.
即：logcat -b 可以打印更多的信息，因为Android log存储的位置不仅有main缓冲区（主缓冲区，比如log.v的log就会存储在main缓冲区），还有’system’, ‘radio’, ‘events’, ‘crash’ 缓冲区。
各个缓冲区的文件系统位置如下：
system: /dev/log/system; main: /dev/log/main; radio: /dev/log/radio; events: /dev/log/events;
各个缓冲区解释如下：
main 主缓冲区（Log.v之类的）； system 系统缓冲区（Slog之类的）； radio 无线/电话之类的； events 事件之类的log；
作用方法如下：
logcat -b system -b main -b radio -b events