46--logcat的使用大全（自我总结）

```shell

//将缓冲区的log打印到屏幕并退出
adb logcat -d 
//清除缓冲区log（testCase运行前可以先清除一下）
adb logcat -c
//打印缓冲区大小并退出
adb logcat -g
//输出log
logcat -r 10000 -v time -f /cache/log/dlog/dlog.log -n 5

```

## 1、logcat -b选项过滤

在Android中不同的log写到不同的设备中，共有`/dev/log/system, /dev/log/main, /dev/log/radio, /dev/log/events`四中类型。其中默认Log.v等写入/dev/log/main中。Slog写入/dev/log/system中。 
    
我们在使用logcat 抓去日至的时候, 可以指定buffer，来请求不同的环形缓冲区 (‘main’, ‘system’, ‘radio’, ‘events’,默认为”-b main system”)，因为android日志系统为日志消息保持了多个循环缓冲区，而且不是所有的消息都被发送到默认缓冲区，要想查看这些附加的缓冲区，可以使用-b 选项，以下是可以指定的缓冲区：　　　 
`main`     — 查看主缓冲区 (默认缓冲区)　　　 
`radio`     — 查看包含在无线/电话相关的缓冲区消息　　　 
`events`    — 查看事件相关的消息 
adb logcat -b
eg:
```
#使用logcat -v threadtime -b events|grep boot查看开机各阶段的时间，看看是否有优化空间
130|root@Hi3798MV200H:/ # logcat -v threadtime -b events|grep boot 
01-01 08:00:00.817  1598  1598 I boot_progress_start: 3917
01-01 08:00:01.637  1598  1598 I boot_progress_preload_start: 4737
09-16 10:15:09.645  1598  1598 I boot_progress_preload_end: 7956
09-16 10:15:09.823  2123  2123 I boot_progress_system_run: 8135
09-16 10:15:10.138  2123  2123 I boot_progress_pms_start: 8450
09-16 10:15:10.221  2123  2123 I boot_progress_pms_system_scan_start: 8533
09-16 10:15:11.048  2123  2123 I boot_progress_pms_data_scan_start: 9360
09-16 10:15:11.054  2123  2123 I boot_progress_pms_scan_end: 9366
09-16 10:15:11.084  2123  2123 I boot_progress_pms_ready: 9395
09-16 10:15:12.462  2123  2123 I boot_progress_ams_ready: 10774
09-16 10:15:18.349  2123  2142 I boot_progress_enable_screen: 16660

```
#抓取各阶段时间节点
platform/android/frameworks/base/services/core/java/com/android/server/SystemService.java 定义：
```
   /*
     * Boot Phases
     */
    public static final int PHASE_WAIT_FOR_DEFAULT_DISPLAY = 100; // maybe should be a dependency?

/**
     * After receiving this boot phase, services can obtain lock settings data.
     */
    public static final int PHASE_LOCK_SETTINGS_READY = 480;

/**
     * After receiving this boot phase, services can safely call into core system services
     * such as the PowerManager or PackageManager.
     */
    public static final int PHASE_SYSTEM_SERVICES_READY = 500;

/**
     * After receiving this boot phase, services can broadcast Intents.
     */
    public static final int PHASE_ACTIVITY_MANAGER_READY = 550;

/**
     * After receiving this boot phase, services can start/bind to third party apps.
     * Apps will be able to make Binder calls into services at this point.
     */
    public static final int PHASE_THIRD_PARTY_APPS_CAN_START = 600;

/**
     * After receiving this boot phase, services can allow user interaction with the device.
     * This phase occurs when boot has completed and the home application has started.
     * System services may prefer to listen to this phase rather than registering a
     * broadcast receiver for ACTION_BOOT_COMPLETED to reduce overall latency.
     */
    public static final int PHASE_BOOT_COMPLETED = 1000;
```
platform/android/frameworks/base/services/java/com/android/server/SystemServer.java 使用
```
130|root@Hi3798MV200H:/ # logcat -v threadtime | grep -iE "Starting phase"
09-16 10:15:10.111  2123  2123 I SystemServiceManager: Starting phase 100
09-16 10:15:12.277  2123  2123 I SystemServiceManager: Starting phase 480
09-16 10:15:12.284  2123  2123 I SystemServiceManager: Starting phase 500
09-16 10:15:12.465  2123  2123 I SystemServiceManager: Starting phase 550
09-16 10:15:13.024  2123  2123 I SystemServiceManager: Starting phase 600
09-16 10:15:19.182  2123  2147 I SystemServiceManager: Starting phase 1000

```

# 2、logcat -v time 打印时间戳同时grep多个条件
`logcat -v time | grep -iE "aaa|bbb|ccc"`

# 3、logcat -v threadtime 打印进程号线程号和时间

# 4、编译log输出到文件，查看编译error等
`./build.sh 2>&1 | tee build1.log`    //编译整个系统
`mm 2>&1 | tee build2.log`     //编译某个module

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