Linux 中 Printk() 和 Printf() 的区别

Question

I am a new user to Linux OS and am currently learning my way in it. I was studying about OS Debugging and related topics and as a basic debugging tool it is recomended to print out certain information regarding the state of the System.

This task can be accomplished by the mentioned functions printf() and also printk() , and have found that the "k" stands for kernel, and is some sort of "primitive" form of print function. Also that printf() is given by the C library rather than the kernel one (not completely sure of the meaning of this).

I was wondering if there is other advantage for using either of them other than the obvious one (which is to use printk() in earlier stages of the booting given that printf() is not yet avialable). Can one obtain the same information when using the two of them?

Answer 1

printk() is a kernel level function, which has the ability to print out to different loglevels as defined in <linux/kernel.h> .

printf() will always print to a file descriptor - STD_OUT

The major difference between printk() and printf() is the capability of the former to specify a loglevel. The kernel uses the loglevel to decide whether to print the message to the console. The kernel displays all messages with a loglevel below a specified value on the console.

More Information Here

Answer 2

printf() is a function in the C Standard Library

You are correct that you would want to use printk() if you did not yet have access to the C libraries yet. printk() gives you printf() functionality where you would not have it otherwise.

A good comparison of the two can be found here

Edit note - replaced dead link with static archive version