adb如何打印kernel输出log

Android内核的Log输出

Android内核是基于Linxu kernel的，因此其log机制也是通用的，在Android内核中使用printk函数进行Log输出。与c语言的printf类似，printk提供格式化输入功能，同时，它也具有所有LOG机制的特点--提供日志级别过虑功能。printk提供了8种日志级别（详细的定义在include/linux/kern_levels.h中）：

#ifndef __KERN_LEVELS_H__#define __KERN_LEVELS_H__#define KERN_SOH        "\001"          /* ASCII Start Of Header */#define KERN_SOH_ASCII  '\001'#define KERN_EMERG      KERN_SOH "0"    /* system is unusable */#define KERN_ALERT      KERN_SOH "1"    /* action must be taken immediately */#define KERN_CRIT       KERN_SOH "2"    /* critical conditions */#define KERN_ERR        KERN_SOH "3"    /* error conditions */#define KERN_WARNING    KERN_SOH "4"    /* warning conditions */#define KERN_NOTICE     KERN_SOH "5"    /* normal but significant condition */#define KERN_INFO       KERN_SOH "6"    /* informational */#define KERN_DEBUG      KERN_SOH "7"    /* debug-level messages */#define KERN_DEFAULT    KERN_SOH "d"    /* the default kernel loglevel *//* * Annotation for a "continued" line of log printout (only done after a * line that had no enclosing \n). Only to be used by core/arch code * during early bootup (a continued line is not SMP-safe otherwise). */#define KERN_CONT       ""#endif

printk的最简单的使用方法：

//KERN_ALERT表示日志级别，后面紧跟着要格式化字符串。printk(KERN_ALERT "This is the log printed by printk in linux kernel space.");

printk的带格式化输出使用方法：

printk(KERN_ERR "%s: Invalid parameter\n", __func__);

adb connect情况下输出kernel打印信息

Android系统中，printk输出的日志信息保存在/proc/kmsg中，要查看/proc/kmsg的内容，只输入在命令行中输入如下命令

shell@rk3288_box:/ # cat  /proc/kmsg

输出结果如图

Paste_Image.png

Android内核的Log输出

adb connect情况下输出kernel打印信息

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