82bc33d5ad
The bit values are numbers given in octal representation, not decimal, as one might assume from the description. Same goes for the base, although this has an example. Reviewed by: emaste MFC after: 3 days Sponsored by: The FreeBSD Foundation Differential Revision: https://reviews.freebsd.org/D39815
190 lines
4.9 KiB
Groff
190 lines
4.9 KiB
Groff
.\"
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.\" Copyright (c) 2001 Andrew R. Reiter
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.\" Copyright (c) 2004 Joerg Wunsch
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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.\" BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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.\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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.\" AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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.\" OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd April 25, 2023
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.Dt PRINTF 9
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.Os
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.Sh NAME
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.Nm printf ,
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.Nm uprintf ,
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.Nm tprintf ,
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.Nm log
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.Nd formatted output conversion
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.Sh SYNOPSIS
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.In sys/types.h
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.In sys/systm.h
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.Ft int
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.Fn printf "const char *fmt" ...
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.Ft void
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.Fn tprintf "struct proc *p" "int pri" "const char *fmt" ...
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.Ft int
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.Fn uprintf "const char *fmt" ...
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.Ft int
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.Fn vprintf "const char *fmt" "va_list ap"
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.In sys/syslog.h
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.Ft void
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.Fn log "int pri" "const char *fmt" ...
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.Ft void
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.Fn vlog "int pri" "const char *fmt" "va_list ap"
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.Sh DESCRIPTION
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The
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.Nm
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family of functions are similar to the
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.Xr printf 3
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family of functions.
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The different functions each use a different output stream.
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The
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.Fn uprintf
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function outputs to the current process' controlling tty, while
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.Fn printf
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writes to the console as well as to the logging facility.
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The
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.Fn tprintf
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function outputs to the tty associated with the process
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.Fa p
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and the logging facility if
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.Fa pri
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is not \-1.
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The
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.Fn log
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function sends the message to the kernel logging facility, using
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the log level as indicated by
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.Fa pri ,
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and to the console if no process is yet reading the log.
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.Pp
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Each of these related functions use the
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.Fa fmt
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parameter in the same manner as
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.Xr printf 3 .
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However,
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.Nm
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adds two other conversion specifiers and omits one.
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.Pp
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The
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.Cm \&%b
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identifier expects two arguments: an
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.Vt int
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and a
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.Vt "char *" .
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These are used as a register value and a print mask for decoding bitmasks.
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The print mask is made up of two parts: the base and the
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arguments.
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The base value is the output base (radix) expressed as an octal value;
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for example, \e10 gives octal and \e20 gives hexadecimal.
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The arguments are made up of a sequence of bit identifiers.
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Each bit identifier begins with an
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.Em octal
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value which is the number of the bit (starting from 1) this identifier
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describes.
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The rest of the identifier is a string of characters containing the name of
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the bit.
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The string is terminated by either the bit number at the start of the next
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bit identifier or
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.Dv NUL
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for the last bit identifier.
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.Pp
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The
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.Cm \&%D
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identifier is meant to assist in hexdumps.
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It requires two arguments: a
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.Vt "u_char *"
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pointer and a
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.Vt "char *"
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string.
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The memory pointed to by the pointer is output in hexadecimal one byte at
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a time.
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The string is used as a delimiter between individual bytes.
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If present, a width directive will specify the number of bytes to display.
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By default, 16 bytes of data are output.
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.Pp
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The
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.Cm \&%n
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conversion specifier is not supported.
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.Pp
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The
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.Fn log
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function uses
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.Xr syslog 3
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level values
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.Dv LOG_DEBUG
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through
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.Dv LOG_EMERG
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for its
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.Fa pri
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parameter (mistakenly called
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.Sq priority
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here).
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Alternatively, if a
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.Fa pri
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of \-1 is given, the message will be appended to the last log message
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started by a previous call to
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.Fn log .
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As these messages are generated by the kernel itself, the facility will
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always be
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.Dv LOG_KERN .
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.Sh RETURN VALUES
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The
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.Fn printf
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and the
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.Fn uprintf
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functions return the number of characters displayed.
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.Sh EXAMPLES
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This example demonstrates the use of the
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.Cm \&%b
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and
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.Cm \&%D
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conversion specifiers.
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The function
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.Bd -literal -offset indent
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void
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printf_test(void)
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{
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printf("reg=%b\en", 3, "\e10\e2BITTWO\e1BITONE");
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printf("out: %4D\en", "AAZZ", ":");
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}
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.Ed
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.Pp
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will produce the following output:
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.Bd -literal -offset indent
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reg=3<BITTWO,BITONE>
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out: 41:41:5a:5a
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.Ed
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.Pp
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The call
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.Bd -literal -offset indent
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log(LOG_DEBUG, "%s%d: been there.\en", sc->sc_name, sc->sc_unit);
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.Ed
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.Pp
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will add the appropriate debug message at priority
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.Dq Li kern.debug
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to the system log.
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.Sh SEE ALSO
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.Xr printf 3 ,
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.Xr syslog 3
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