printk - print messages to console log

SYNOPSIS

       #include <linux/kernel.h>

       int printk(const char*fmt, ...)

DESCRIPTION

       Print a formatted message to the kernel console, much like
       the printf function of the stdio  library.  Normally,  the
       message  is  written to the physical console device of the
       computer, 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  prior­
       ity code, which sets the priority of the message. The pri­
       ority 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:

              KERN_EMERG
                     System is unuseable

              KERN_ALERT
                     Action must be taken immediately

              KERN_CRIT
                     Critical conditions

              KERN_ERR
                     Error conditions

              KERN_WARNING
                     Warning conditions

              KERN_NOTICE
                     Normal but significant condition

              KERN_INFO
                     Informational

              KERN_DEBUG
                     Debug-level messages

       For example

            printk(KERN_NOTICE "Hello, world.\n");

       does the expected thing.

RETURN VALUE

       Linux 1.0+

SEE ALSO

       register_console(9), syslog(2)

       kernel/printk.c

AUTHOR

       Stephen Williams (steve@icarus.com)

BUGS

       float and double formats are  not  supported.  Floats  and
       doubles do not belong inside the kernel anyhow.

       The  printk  implementation protects itself from interrup­
       tion, so in principle it can be used  in  interrupts  han­
       dlers and critical sections. However, there are no guaran­
       tees about the console function that is registered.