NAME
printf, uprintf,
tprintf, log —
formatted output conversion
SYNOPSIS
#include
<sys/types.h>
#include <sys/systm.h>
int
printf(const
char *fmt,
...);
void
tprintf(struct
proc *p, int pri,
const char *fmt,
...);
int
uprintf(const
char *fmt,
...);
int
vprintf(const
char *fmt, va_list
ap);
#include
<sys/syslog.h>
void
log(int
pri, const char
*fmt, ...);
void
vlog(int
pri, const char
*fmt, va_list
ap);
DESCRIPTION
The printf family of functions are similar
to the
printf(3) family of functions. The different functions each
use a different output stream. The
uprintf()
function outputs to the current process' controlling tty, while
printf()
writes to the console as well as to the logging facility. The
tprintf()
function outputs to the tty associated with the process
p and the logging facility if
pri is not -1. The log()
function sends the message to the kernel logging facility, using the log
level as indicated by pri, and to the console if no
process is yet reading the log.
Each of these related functions use the fmt
parameter in the same manner as
printf(3). However, printf adds two
other conversion specifiers and omits one.
The %b identifier expects two
arguments: an int and a char *.
These are used as a register value and a print mask for decoding bitmasks.
The print mask is made up of two parts: the base and the arguments. The base
value is the output base (radix) expressed as an octal value; for example,
\10 gives octal and \20 gives hexadecimal. The arguments are made up of a
sequence of bit identifiers. Each bit identifier begins with an
octal value which
is the number of the bit (starting from 1) this identifier describes. The
rest of the identifier is a string of characters containing the name of the
bit. The string is terminated by either the bit number at the start of the
next bit identifier or NUL for the last bit
identifier.
The %D identifier is meant to assist in
hexdumps. It requires two arguments: a u_char *
pointer and a char * string. The memory pointed to by
the pointer is output in hexadecimal one byte at a time. The string is used
as a delimiter between individual bytes. If present, a width directive will
specify the number of bytes to display. By default, 16 bytes of data are
output.
The %n conversion specifier is not
supported.
The
log() function
uses syslog(3) level values LOG_DEBUG
through LOG_EMERG for its pri
parameter (mistakenly called ‘priority’ here). Alternatively,
if a pri of -1 is given, the message will be appended
to the last log message started by a previous call to
log(). As these messages are generated by the kernel
itself, the facility will always be LOG_KERN.
RETURN VALUES
The printf() and the
uprintf() functions return the number of characters
displayed.
EXAMPLES
This example demonstrates the use of the
%b and %D conversion
specifiers. The function
void
printf_test(void)
{
printf("reg=%b\n", 3, "\10\2BITTWO\1BITONE");
printf("out: %4D\n", "AAZZ", ":");
}
will produce the following output:
reg=3<BITTWO,BITONE> out: 41:41:5a:5a
The call
log(LOG_DEBUG, "%s%d: been there.\n", sc->sc_name, sc->sc_unit);
will add the appropriate debug message at priority
“kern.debug” to the system log.