KPRINTF(9) BSD Kernel Developer's Manual KPRINTF(9)NAME
device_printf, printf, snprintf, vprintf, vsnprintf, uprintf, ttyprintf,
tprintf, aprint — kernel formatted output conversion
SYNOPSIS
#include <sys/systm.h>
void
device_printf(device_t, const char *format, ...);
void
printf(const char *format, ...);
void
printf_nolog(const char *format, ...);
int
snprintf(char *buf, size_t size, const char *format, ...);
void
vprintf(const char *format, va_list ap);
int
vsnprintf(char *buf, size_t size, const char *format, va_list ap);
void
uprintf(const char *format, ...);
void
ttyprintf(struct tty *tty, const char *format, ...);
#include <sys/tprintf.h>
tpr_t
tprintf_open(struct proc *p);
void
tprintf(tpr_t tpr, const char *format, ...);
void
tprintf_close(tpr_t tpr);
void
aprint_normal(const char *format, ...);
void
aprint_naive(const char *format, ...);
void
aprint_verbose(const char *format, ...);
void
aprint_debug(const char *format, ...);
void
aprint_error(const char *format, ...);
void
aprint_normal_dev(device_t, const char *format, ...);
void
aprint_naive_dev(device_t, const char *format, ...);
void
aprint_verbose_dev(device_t, const char *format, ...);
void
aprint_debug_dev(device_t, const char *format, ...);
void
aprint_error_dev(device_t, const char *format, ...);
void
aprint_normal_ifnet(struct ifnet *, const char *format, ...);
void
aprint_naive_ifnet(struct ifnet *, const char *format, ...);
void
aprint_verbose_ifnet(struct ifnet *, const char *format, ...);
void
aprint_debug_ifnet(struct ifnet *, const char *format, ...);
void
aprint_error_ifnet(struct ifnet *, const char *format, ...);
int
aprint_get_error_count(void);
DESCRIPTION
The printf() family of functions allows the kernel to send formatted mes‐
sages to various output devices. The functions printf() and vprintf()
send formatted strings to the system console. The device_printf() func‐
tion is identical to printf(), except that it prefixes the log message
with the corresponding device name. The printf_nolog() function is iden‐
tical to printf(), except it does not send the data to the system log.
The functions snprintf() and vsnprintf() write output to a string buffer.
These four functions work similarly to their user space counterparts, and
are not described in detail here.
The functions uprintf() and ttyprintf() send formatted strings to the
current process's controlling tty and a specific tty, respectively.
The tprintf() function sends formatted strings to a process's controlling
tty, via a handle of type tpr_t. This allows multiple write operations
to the tty with a guarantee that the tty will be valid across calls. A
handle is acquired by calling tprintf_open() with the target process as
an argument. This handle must be closed with a matching call to
tprintf_close().
The functions aprint_normal(), aprint_naive(), aprint_verbose(),
aprint_debug(), and aprint_error() are intended to be used to print
autoconf(9) messages. Their verbosity depends on flags set in the
boothowto variable, through options passed during bootstrap; see
boothowto(9) and Interactive mode in boot(8):
AB_SILENT silent mode, enabled by boot -z.
AB_QUIET quiet mode, enabled by boot -q.
AB_VERBOSE verbose mode, enabled by boot -v.
AB_DEBUG debug mode, enabled by boot -x.
The aprint_*() functions have the following behaviour, based on the above
mentioned flags:
aprint_normal() Sends to the console unless AB_QUIET is set. Always
sends to the log.
aprint_naive() Sends to the console only if AB_QUIET is set. Never
sends to the log.
aprint_verbose() Sends to the console only if AB_VERBOSE is set.
Always sends to the log.
aprint_debug() Sends to the console and the log only if AB_DEBUG is
set.
aprint_error() Like aprint_normal(), but also keeps track of the
number of times called. This allows a subsystem to
report the number of errors that occurred during a
quiet or silent initialization phase.
For the aprint_*() functions there are two additional families of func‐
tions with the suffixes _dev and _ifnet which work like their counter‐
parts without the suffixes, except that they take a device_t and struct
ifnet *, respectively, as first argument, and prefix the log message with
the corresponding device or interface name.
The aprint_get_error_count() function reports the number of errors and
resets the counter to 0.
If AB_SILENT is set, none of the autoconfiguration message printing rou‐
tines send output to the console. The AB_VERBOSE and AB_DEBUG flags
override AB_SILENT.
RETURN VALUES
The snprintf() and vsnprintf() functions return the number of characters
placed in the buffer buf. This is different to the user-space functions
of the same name.
The tprintf_open() function returns NULL if no terminal handle could be
acquired.
SEE ALSOprintf(1), printf(3), snprintb(3), boot(8), autoconf(9), boothowto(9)CODE REFERENCES
sys/kern/subr_prf.c
HISTORY
The sprintf() and vsprintf() unsized string formatting functions are sup‐
ported for compatibility only, and are not documented here. New code
should use the size-limited snprintf() and vsnprintf() functions instead.
In NetBSD 1.5 and earlier, printf() supported more format strings than
the user space printf(). These nonstandard format strings are no longer
supported. For the functionality provided by the former %b format
string, see snprintb(3).
The aprint_normal(), aprint_naive(), aprint_verbose(), and aprint_debug()
functions first appeared in BSD/OS.
BUGS
The uprintf() and ttyprintf() functions should be used sparingly, if at
all. Where multiple lines of output are required to reach a process's
controlling terminal, tprintf() is preferred.
BSD January 21, 2011 BSD
