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PRINTF(9)		 BSD Kernel Developer's	Manual		     PRINTF(9)

     printf, uprintf, tprintf, log -- formatted	output conversion

     #include <sys/types.h>
     #include <sys/systm.h>

     printf(const char *fmt, ...);

     tprintf(struct proc *p, int pri, const char *fmt, ...);

     uprintf(const char	*fmt, ...);

     log(int pri, const	char *fmt, ...);

     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 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	argu-
     ments: 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	direc-
     tive 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).  Al-
     ternatively, 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.

     The printf() and the uprintf() functions return the number	of characters

     This example demonstrates the use of the %b and %D	conversion specifiers.
     The function


		   printf("reg=%b\n", 3, "\10\2BITTWO\1BITONE\n");
		   printf("out:	%4D\n",	"AAAA",	":");

     will produce the following	output:

	   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 sys-
     tem log.

     printf(3),	syslog(3)

BSD				August 10, 2004				   BSD


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