printf man page on MirBSD

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PRINTF(9)		      BSD Kernel Manual			     PRINTF(9)

NAME
     printf, snprintf, vprintf, vsnprintf, uprintf, ttyprintf, db_printf -
     kernel formatted output conversion

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

     int
     printf(const char *format, ...);

     int
     snprintf(char *buf, size_t size, const char *format, ...);

     int
     vprintf(const char *format, va_list ap);

     int
     vsnprintf(char *buf, size_t size, const char *fmt, va_list ap);

     void
     uprintf(const char *format, ...);

     void
     ttyprintf(struct tty *tty, const char *format, ...);

     void
     db_printf(const char *format, ...);

DESCRIPTION
     The printf(), snprintf(), vprintf(), vsnprintf(), uprintf(), ttyprintf(),
     and db_printf() functions allow the kernel to send formatted messages to
     various output devices. The functions printf() and vprintf() send format-
     ted strings to the system console and to the system log. The functions
     uprintf() and ttyprintf() send formatted strings to the current process's
     controlling tty and a specific tty, respectively. The function
     db_printf() sends formatted strings to the ddb console, and is only used
     to implement ddb(4).

     Since each of these kernel functions is a variant of its user space coun-
     terpart, this page describes only the differences between the user space
     and kernel versions. Refer to printf(3) for functional details.

  FORMAT OPTIONS
     The kernel functions don't support any floating point formatting specif-
     iers. In addition to other formatting specifiers common with the user
     space functions, the kernel functions accept the following format specif-
     iers in the format string format:

     %b	   Bit field expansion. This format specifier is useful for decoding
	   bit fields in device registers. It displays an integer using a
	   specified radix (base) and an interpretation of the bits within
	   that integer as though they were flags. It requires two arguments
	   from the argument vector, the first argument being the bit field to
	   be decoded (as an integer) and the second being a decoding direc-
	   tive string.

	   The decoding directive string describes how the bitfield is to be
	   interpreted and displayed. The first character of the string is a
	   binary character representation of the output numeral base in which
	   the bitfield will be printed before it is decoded. Recognized radix
	   values (in C escape-character format) are \10 (octal), \12
	   (decimal), and \20 (hexadecimal).

	   The remaining characters in the decoding directive string are in-
	   terpreted as a list of bit-positiondescription pairs. A bit-
	   positiondescription pair begins with a binary character value that
	   represents the position of the bit being described. A bit position
	   value of one describes the least significant bit. Whereas a posi-
	   tion value of 32 (octal 40, hexadecimal 20, the ASCII space
	   character) describes the most significant bit.

	   The remaining characters in a bit-positiondescription pair are the
	   characters to print should the bit being described be set. Descrip-
	   tion strings are delimited by the next bit position value character
	   encountered (distinguishable by its value being _ 32), or the end
	   of the decoding directive string itself.

     %r	   Displays an integer using the current DDB radix. This non-standard
	   interpretation of %r is only available to db_printf().

     %z	   Displays a signed integer using the C-style hexadecimal constant
	   format. This format specifier is only available to db_printf().

RETURN VALUES
     The printf(), snprintf(), vprintf(), and vsnprintf() functions return the
     number of characters they placed in the buffer buf.

EXAMPLES
     Use of the %b format specifier for decoding device registers.

	   printf("reg=%b\n", 3, "\10\2BITTWO\1BITONE")
	    "reg=3<BITTWO,BITONE>"

	   printf("enablereg=%b\n", 0xe860,
		  "\20\x10NOTBOOT\x0fFPP\x0eSDVMA\x0cVIDEO"
		  "\x0bLORES\x0aFPA\x09DIAG\x07CACHE"
		  "\x06IOCACHE\x05LOOPBACK\x04DBGCACHE")
	    "enablereg=e860<NOTBOOT,FPP,SDVMA,VIDEO,CACHE,IOCACHE>"

SEE ALSO
     revoke(2), printf(3), ddb(4), log(9)

CODE REFERENCES
     sys/kern/subr_prf.c

LIMITATIONS
     The %b format specifier cannot be used to decode integers greater than 32
     bits in size.

MirOS BSD #10-current	      September 1, 1998				     1
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