Android中logcat和日志打印

 一、logcat对日志过滤

1.# logcat --help

# 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 （优先级最低）
  D    Debug
  I    Info
  W    Warn
  E    Error
  F    Fatal
  S    Silent (supress all output) （最高优先级，不会打印任何内容）

'*' 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"

1. logcat命令位置：/system/bin/logcat

2.logcat的常用用法

# logcat *:W 过滤日志则会将该级别及以上的日志输出

# logcat ActivityManager:I MyApp:D *:S 表示输出tag=“ActivityManager”的Info以上级别日志，输出tag=“MyApp”的Debug以上级别日志，及其它tag的Silent级别日志（即屏蔽其它 tag 日志）。

# logcat -d logcat应该是动态打印的，加-d后打印完log后退出，不阻塞
# logcat -t 20 只打印最近的20行log，-T也是类似的功能，但是打印完后不退出。
# logcat -f a.txt -f保存到文件中，不使用重定向符号的
# logcat | grep -i myapp 忽略大小写。
# logcat | grep --color=auto -i priv-app 匹配到的“priv-app”会显示出颜色
# logcat | grep --color=auto 1979 只打印出进程PID为1979的log
# logcat -c && logcat
# logcat -v time 打印时加上时间
# logcat -g 打印各个环形缓冲区的大小后退出
# logcat -S 打印出统计信息
# logcat | grep -E "Theft|u-blox" grep -E 正则表达式,可以一次性检索多个关键字
# logcat <tag1>:<priority1> <tag2>:<priority2> 过滤低优先级的日志

# logcat *:E 　　只查看错误打印

3.有 3 种方式使用 logcat 打印日志：
可以通过 IDE(比如 Android Studio)提供的 logcat 窗口查看打印的日志
可以通过 adb 命令使用 logcat 在本地计算机进行日志查看
通过 adb 命令进入模拟器或者所连设备的 shell 命令窗口，进行 logcat 的操作和使用

4.设置输出日志等级
通过设置优先级，过滤掉低优先级的日志，使用方式如: adb logcat <tag1>:<priority1> <tag2>:<priority2>
示例: logcat PowerManagerService:I PackageManager:I 表示logcat时不打印PowerManagerService和PackageManager的优先级低于Info的log

5.logcat选择打印的缓冲区：
# logcat -b <buffer> 可以指定要打印的环缓冲区，“main”，“system”，“radio”或“events”。 允许多个-b连用，这样打印的结果是交错的，默认为: -b main -b system -b crash。
radio - 查看缓冲区的相关的信息.
events - 查看和事件相关的的缓冲区.
main - 查看主要的日志缓冲区.
system - 与系统相关的日志信息.

6. logcat默认的几种输出格式为

格式：logcat -v threadtime

(1)brief格式为：<priority>/<tag>(<pid>): <message>  eg: D/HeadsetStateMachine( 1785): Disconnected process message: 10, size: 0

(2)process格式为：<priority>(<pid>) <message>  eg: D( 1785) Disconnected process message: 10, size: 0 (HeadsetStateMachine)

(3)tag格式为：<priority>/<tag>: <message>  eg: D/HeadsetStateMachine: Disconnected process message: 10, size: 0

(4)raw格式为：<message>   eg: Disconnected process message: 10, size: 0

(5)time格式为：<datetime> <priority>/<tag>(<pid>): <message>  eg: 08-28 22:39:39.974 D/HeadsetStateMachine( 1785): Disconnected process message: 10, size: 0

(6)threadtime格式为：<datetime> <pid> <tid> <priority> <tag>: <message>  eg: 08-28 22:39:39.974 1785 1832 D HeadsetStateMachine: Disconnected process message: 10, size: 0

(7)long格式为：[ <datetime> <pid>:<tid> <priority>/<tag> ] <message>  eg: [ 08-28 22:39:39.974 1785: 1832 D/HeadsetStateMachine ] Disconnected process  message: 10, size: 0

二、日志打印函数

1.程序中使用ALOGx(),SLOGx(),RLOGx()来分别打印app,system,radio的log,

x表示下面6种打印级别：
V Verbose
D Debug
I Info
W Warn
E Error
F Fatal

比如：
#define LOG_TAG "LedHal"
ALOGI("hal_led_ioctl called: which=%d, status=%d", which, status);
打印如下：

I/LedHal ( 2284): hal_led_ioctl called: which=0, status=0 //打印等级/Tag (PID): message

三、日志统计

1.# logcat -b all -S 可以统计出各个log buffer中最健谈的log的进程、UID、TAG

# logcat -b all -S
size/num main               radio              events             system             crash  stats    performance   security           kernel             Total
Total    /      /       /        /      /   /     /      /                /                /
Now      /        /        /        /        /           /                                            /
Logspan  ::38.987(3.9%)  ::44.731(24.2%) ::41.166(96.9%) ::44.791(%)   :03.21         ::35.716                                         ::48.058
Overhead
update time=, report time=, buffer rate =  Byte/sec, log rate =  sec-
buffer chatty rate =  Byte/sec, log chatty rate =  sec-

最健谈的main log：
Chattiest UIDs in main log buffer:                           Size   +/-  Pruned
UID   PACKAGE                                               BYTES           NUM
 com.android.systemui                                    -%
  system                                                  -%
  PID/UID   COMMAND LINE                                       "             "
 /  system_server
 /  com.coloros.persist.system                                  

最健谈的main log：
Chattiest UIDs in radio log buffer:                          Size   +/-  Pruned
UID   PACKAGE                                               BYTES           NUM
  radio                                                  -3.6%
  system                                                  .2X

最健谈的event log：
Chattiest UIDs in events log buffer:                         Size   +/-  Pruned
UID   PACKAGE                                               BYTES           NUM
  system                                                 +4.3%
  PID/UID   COMMAND LINE                                       "             "
 /  system_server                                              

最健谈的system log：
Chattiest UIDs in system log buffer:                         Size   +/-  Pruned
UID   PACKAGE                                               BYTES           NUM
  system                                                 -%
  PID/UID   COMMAND LINE                                       "             "
 /  system_server
 /  com.coloros.persist.system                                 

最健谈的crash log：
Chattiest UIDs in crash log buffer:                          Size
UID   PACKAGE                                               BYTES
     root                                                    

最健谈的performance log：
Chattiest UIDs in performance log buffer:                    Size
UID   PACKAGE                                               BYTES
  system
  PID/UID   COMMAND LINE                                       "
 /  system_server                                     

最健谈的PID:
Chattiest PIDs:                                              Size        Pruned
  PID/UID   COMMAND LINE                                    BYTES           NUM
 /  com.android.phone
 /  system_server                                           

最健谈的TID:
Chattiest TIDs:                                              Size        Pruned
  TID/UID   COMM                                            BYTES           NUM
 /  com.android.phone
 /  android.bg                                                 

最健谈的events log中的TAG:
Chattiest events log buffer TAGs:                            Size         Prune
    TAG/UID   TAGNAME                                       BYTES           NUM
          auditd
  /  am_pss                                        

最健谈的TAG：
Chattiest TAGs:                                              Size
  TID/PID/UID   LOG_TAG NAME                                BYTES
     /  SST
                auditd