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' 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.
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
bitmasks. The print mask is made up of two parts: the base and the arguments.
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 (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 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 default, 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
‘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\n");
printf("out: %4D\n", "AAAA", ":");
}
will produce the following output:
reg=3<BITTWO,BITONE>
out: 41:41:41:41
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.
SEE ALSO¶
printf(3),
syslog(3)