shell@xxx:/ $ ls /dev/log -l

crw-rw-rw- root     log       ,   -- : events

crw-rw-rw- root     log       ,   -- : main

crw-rw-rw- root     log       ,   -- : radio

crw-rw-rw- root     log       ,   -- : system

shell@xxx:/ $ logcat --help

Usage: logcat [options] [filterspecs]

options include:

  -s              Set default filter to silent.

                  Like specifying filterspec '*:s'

  -f <filename>   Log to file. Default to stdout

  -r [<kbytes>]   Rotate log every kbytes. ( if unspecified). Requires -f

  -n <count>      Sets max number of rotated logs to <count>, default

  -v <format>     Sets the log print format, where <format> is one of:

                  brief process tag thread raw time threadtime long

  -c              clear (flush) the entire log and exit

  -d              dump the log and then exit (don't block)

  -t <count>      print only the most recent <count> lines (implies -d)

  -t '<time>'     print most recent lines since specified time (implies -d)

  -T <count>      print only the most recent <count> lines (does not imply -d)

  -T '<time>'     print most recent lines since specified time (not imply -d)

                  count is pure numerical, time is 'MM-DD hh:mm:ss.mmm'

  -g              get the size of the log's ring buffer and exit

  -b <buffer>     Request alternate ring buffer, 'main', 'system', 'radio',

                  'events', 'crash' or 'all'. Multiple -b parameters are

                  allowed and results are interleaved. The default is

                  -b main -b system -b crash.

  -B              output the log in binary.

  -S              output statistics.

  -G <size>       set size of log ring buffer, may suffix with K or M.

  -p              print prune white and ~black list. Service is specified as

                  UID, UID/PID or /PID. Weighed for quicker pruning if prefix

                  with ~, otherwise weighed for longevity if unadorned. All

                  other pruning activity is oldest first. Special case ~!

                  represents an automatic quicker pruning for the noisiest

                  UID as determined by the current statistics.

  -P '<list> ...' set prune white and ~black list, using same format as

                  printed above. Must be quoted.

filterspecs are a series of

  <tag>[:priority]

where <tag> is a log component tag (or * for all) and priority is:

  V    Verbose

  D    Debug

  I    Info

  W    Warn

  E    Error

  F    Fatal

  S    Silent (supress all output)

'*' means '*:d' and <tag> by itself means <tag>:v

If not specified on the commandline, filterspec is set from ANDROID_LOG_TAGS.

If no filterspec is found, filter defaults to '*:I'

If not specified with -v, format is set from ANDROID_PRINTF_LOG

or defaults to "brief"

// 打印标签为"NetworkController"的所有日志

shell@xxx:/ $ logcat -s "NetworkController"

// 打印标签为"NetworkController"，并且等级为 D 的日志

shell@xxx:/ $ logcat -s "NetworkController:D"

shell@xxx:/ # logcat -f /data/local/tmp/log.txt

// 日志添加时间（最常用）

shell@xxx:/ # logcat -v time

shell@xxx:/ # logcat -c

shell@xxx:/ # logcat -d

shell@xxx:/ # logcat -t 

shell@xxx:/ # logcat -g

main: ring buffer is 256Kb (7Kb consumed), max entry is 5120b, max payload is 4076b

system: ring buffer is 256Kb (3Kb consumed), max entry is 5120b, max payload is 4076b

crash: ring buffer is 256Kb (0b consumed), max entry is 5120b, max payload is 4076b

shell@xxx:/ # logcat -b main -b radio

shell@xxx:/ # logcat -B

shell@xxx:/ # logcat -S

shell@xxx:/ # logcat -G 256Kb

shell@xxx:/ # logcat -b main -b system -b radio -v time |grep SETUP_DATA_CALL

shell@xxx:/ #  logcat -b radio -v time > d:/log.txt