35 lines
983 B
Markdown
35 lines
983 B
Markdown
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# Linux Kernel 打印输出
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## printk
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**函数原型：**
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```cpp
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int printk(const char *fmt, ...);
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```
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**说明：**
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内核打印输出函数，可通过 dmesg 查看其输出信息。printk 可设置打印级别，如下：
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```cpp
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#define KERN_EMERG "<0>" /* system is unusable */
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#define KERN_ALERT "<1>" /* action must be taken immediately */
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#define KERN_CRIT "<2>" /* critical conditions */
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#define KERN_ERR "<3>" /* error conditions */
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#define KERN_WARNING "<4>" /* warning conditions */
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#define KERN_NOTICE "<5>" /* normal but significant condition */
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#define KERN_INFO "<6>" /* informational */
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#define KERN_DEBUG "<7>" /* debug-level messages */
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```
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dmesg 可通过打印级别过滤消息。
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**参数：**
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fmt：格式化输出字符串。可使用 %d，%s，%c 等。
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**返回值：**
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实际输出的字符个数。
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