printk

Section: Kernel Functions (9)
Updated: $Date:$
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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 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 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 doubles 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.


 

Index

NAME
SYNOPSIS
DESCRIPTION
RETURN VALUE
AVAILABILITY
SEE ALSO
AUTHOR
BUGS
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