printf(9)

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, ...);
#include <sys/syslog.h>
void
log(int pri, const char *fmt, ...);

DESCRIPTION

The printf(9) 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' con
trolling tty,
while printf() writes to the console as well as to the log
ging facility.
The tprintf() function outputs to the tty associated with
the process p
and the logging facility if pri is not -1. The log() func
tion sends the
message to the kernel logging facility, using the log level
as indicated
by pri.
Each of these related functions use the fmt parameter in the
same manner
as printf(3). However, printf(9) adds two other conversion
specifiers.
The %b identifier expects two arguments: an int and a char
*. These are
used as a register value and a print mask for decoding bit
masks. The
print mask is made up of two parts: the base and the argu
ments. The base
value is the output base expressed as an integer 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 integer
value which is the number of the bit this identifier de
scribes. 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 re
quires two arguments: a u_char * pointer and a char * string. The memory
pointed to be
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 de
fault, 16 bytes
of data are output.
The log() function uses syslog(3) level values LOG_DEBUG
through
LOG_EMERG for its pri parameter (mistakenly called `priori
ty' 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 conver
sion specifiers.
The function

void
printf_test(void)
{

printf("reg=%b0, 3, "102BITTWO1BITONE0);
printf("out: %4D0, "AAAA", ":");
}
will produce the following output:

reg=3<BITTWO,BITONE>
out: 41:41:41:41
The call

log(LOG_DEBUG, "%s%d: been there.0, sc->sc_name,
sc->sc_unit);
will add the appropriate debug message at priority
``kern.debug'' to the
system log.

SEE ALSO

printf(3), syslog(3)
BSD August 10, 2004
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