NAME

     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 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:

          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

     Returns the number of characters written to the log.

AVAILABILITY

     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  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.