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

BSD