What is "printk"

printk is a function that prints messages and is used in the C Programming Language exclusively for the Linux Kernel. It accepts a string parameter called the format string, which specifies a method for rendering an arbitrary number of varied data type parameter(s) into a string. The string is then printed to the kernel log.

It provides a printf-like abstraction and its parsing of the format string and arguments behave exactly the same way. It acts as a debugging tool for kernel programmers who need this function for logging messages from the kernel.

The printk function prototype is:

In kernel mode, you can't use the standard C library, so printf is not available, hence printk.