printk - print messages to console log
int printk(const char*fmt, ...)
Print a formatted message to the kernel console, much like
the printf function of the stdio library. Normally, the mes-
sage is written to the physical console device of the com-
puter, although this behavior can be changed with the
register_console function. Messages are also stored in a
message log book.
The generated string may also start with a message priority
code, which sets the priority of the message. The priority
code strings are of the form <n> where n is a number from 0
- 7. The following macros are defined in the
<linux/kernel.h> header file:
System is unuseable
Action must be taken immediately
Normal but significant condition
printk(KERN_NOTICE "Hello, world.\n");
does the expected thing.
Returns the number of characters written to the log.
Stephen Williams (email@example.com)
float and double formats are not supported. Floats and dou-
bles do not belong inside the kernel anyhow.
The printk implementation protects itself from interruption,
so in principle it can be used in interrupts handlers and
critical sections. However, there are no guarantees about
the console function that is registered.