printk的日志级别定义如下(在linux/kernel.h中):
#define KERN_EMERG "<0>"/*紧急事件消息,系统崩溃之前提示,表示系统不可用*/
#define KERN_ALERT "<1>"/*报告消息,表示必须立即采取措施*/
#define KERN_CRIT "<2>"/*临界条件,通常涉及严重的硬件或软件操作失败*/
#define KERN_ERR "<3>"/*错误条件,驱动程序常用KERN_ERR来报告硬件的错误*/
#define KERN_WARNING "<4>"/*警告条件,对可能出现问题的情况进行警告*/
#define KERN_NOTICE "<5>"/*正常但又重要的条件,用于提醒。常用于与安全相关的消息*/
#define KERN_INFO "<6>"/*提示信息,如驱动程序启动时,打印硬件信息*/
#define KERN_DEBUG "<7>"/*调试级别的消息*/
使用举例:
printk(KERN_INFO "INFO\n"); //可以使用数字代替 KERN_INFO
printk(<6> "INFO\n"); //使用数字
printk("INFO\n"); //默认是4
注:
当 printk() 中的消息日志级别小于当前控制台日志级别时,printk 的信息(要有/n符)就会在控制台上显示。但无论当前控制台日志级别是何值,通过dmesg总能查看。
通过读写/proc/sys/kernel/printk文件可读取和修改控制台的日志级别。
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分别对应控制台日志级别、默认的消息日志级别、最低的控制台日志级别和默认的控制台日志级别。
可用下面的命令设置当前日志级别:
# echo 8 > /proc/sys/kernel/printk