adb如何打印kernel输出log

╰+攻爆jí腚メ 2022-06-01 02:11 343阅读 0赞

https://www.jianshu.com/p/9b657c3c3560

# adb如何打印kernel输出log #

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[J\_Coder][96 1]

2016.06.13 20:23\*  字数 198 阅读 2665 评论 1 喜欢 1

### 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

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[96]: /images/20220601/5ee79a8820a64084b97b9dc3a8282181.png|/images/20220601/5ee79a8820a64084b97b9dc3a8282181.png
[96 1]: https://www.jianshu.com/u/c8247d975e68
[677]: /images/20220601/7d3e1faa3fcc4250a66fb0d704e17cca.png