176 lines
4.6 KiB
Groff
176 lines
4.6 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 September 8, 2006
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.Dt PRINTF 9
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.Os
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.Sh NAME
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.Nm printf , uprintf , tprintf, 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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.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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.Sh DESCRIPTION
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The
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.Xr printf 9
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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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.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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.Xr printf 9
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adds two other conversion specifiers.
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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 expressed as an integer 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 integer value which is the number of the
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bit (starting from 1) this identifier 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 be 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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.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\en");
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printf("out: %4D\en", "AAAA", ":");
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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: 41:41:41:41
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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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