ac2adfb86d
* Add examples showing the use of -f, -C, -s, -n * Rework the two already present examples that were *format* examples * Remove .Tn suggested by mandoc(1) * Remove reference to gdb(1) since it is not present in current Approved by: manpages (gbe) Differential Revision: https://reviews.freebsd.org/D25406
388 lines
12 KiB
Groff
388 lines
12 KiB
Groff
.\" Copyright (c) 1989, 1990, 1993
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.\" The Regents of the University of California. 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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.\" 3. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, 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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.\" @(#)hexdump.1 8.2 (Berkeley) 4/18/94
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.\" $FreeBSD$
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.\"
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.Dd June 29, 2020
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.Dt HEXDUMP 1
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.Os
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.Sh NAME
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.Nm hexdump , hd
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.Nd ASCII, decimal, hexadecimal, octal dump
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.Sh SYNOPSIS
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.Nm
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.Op Fl bcCdovx
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.Op Fl e Ar format_string
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.Op Fl f Ar format_file
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.Op Fl n Ar length
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.Bk -words
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.Op Fl s Ar offset
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.Ek
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.Ar
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.Nm hd
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.Op Fl bcdovx
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.Op Fl e Ar format_string
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.Op Fl f Ar format_file
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.Op Fl n Ar length
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.Bk -words
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.Op Fl s Ar offset
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.Ek
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.Ar
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.Sh DESCRIPTION
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The
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.Nm
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utility is a filter which displays the specified files, or
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the standard input, if no files are specified, in a user specified
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format.
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.Pp
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The options are as follows:
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.Bl -tag -width indent
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.It Fl b
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.Em One-byte octal display .
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Display the input offset in hexadecimal, followed by sixteen
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space-separated, three column, zero-filled, bytes of input data,
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in octal, per line.
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.It Fl c
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.Em One-byte character display .
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Display the input offset in hexadecimal, followed by sixteen
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space-separated, three column, space-filled, characters of input
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data per line.
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.It Fl C
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.Em Canonical hex+ASCII display .
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Display the input offset in hexadecimal, followed by sixteen
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space-separated, two column, hexadecimal bytes, followed by the
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same sixteen bytes in %_p format enclosed in ``|'' characters.
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.Pp
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Calling the command
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.Nm hd
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implies this option.
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.It Fl d
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.Em Two-byte decimal display .
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Display the input offset in hexadecimal, followed by eight
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space-separated, five column, zero-filled, two-byte units
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of input data, in unsigned decimal, per line.
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.It Fl e Ar format_string
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Specify a format string to be used for displaying data.
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.It Fl f Ar format_file
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Specify a file that contains one or more newline separated format strings.
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Empty lines and lines whose first non-blank character is a hash mark
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.Pf ( Cm \&# )
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are ignored.
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.It Fl n Ar length
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Interpret only
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.Ar length
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bytes of input.
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.It Fl o
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.Em Two-byte octal display .
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Display the input offset in hexadecimal, followed by eight
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space-separated, six column, zero-filled, two byte quantities of
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input data, in octal, per line.
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.It Fl s Ar offset
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Skip
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.Ar offset
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bytes from the beginning of the input.
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By default,
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.Ar offset
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is interpreted as a decimal number.
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With a leading
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.Cm 0x
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or
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.Cm 0X ,
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.Ar offset
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is interpreted as a hexadecimal number,
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otherwise, with a leading
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.Cm 0 ,
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.Ar offset
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is interpreted as an octal number.
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Appending the character
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.Cm b ,
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.Cm k ,
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or
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.Cm m
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to
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.Ar offset
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causes it to be interpreted as a multiple of
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.Li 512 ,
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.Li 1024 ,
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or
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.Li 1048576 ,
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respectively.
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.It Fl v
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Cause
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.Nm
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to display all input data.
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Without the
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.Fl v
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option, any number of groups of output lines, which would be
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identical to the immediately preceding group of output lines (except
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for the input offsets), are replaced with a line comprised of a
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single asterisk.
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.It Fl x
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.Em Two-byte hexadecimal display .
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Display the input offset in hexadecimal, followed by eight, space
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separated, four column, zero-filled, two-byte quantities of input
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data, in hexadecimal, per line.
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.El
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.Pp
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For each input file,
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.Nm
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sequentially copies the input to standard output, transforming the
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data according to the format strings specified by the
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.Fl e
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and
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.Fl f
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options, in the order that they were specified.
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.Ss Formats
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A format string contains any number of format units, separated by
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whitespace.
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A format unit contains up to three items: an iteration count, a byte
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count, and a format.
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.Pp
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The iteration count is an optional positive integer, which defaults to
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one.
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Each format is applied iteration count times.
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.Pp
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The byte count is an optional positive integer.
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If specified it defines the number of bytes to be interpreted by
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each iteration of the format.
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.Pp
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If an iteration count and/or a byte count is specified, a single slash
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must be placed after the iteration count and/or before the byte count
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to disambiguate them.
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Any whitespace before or after the slash is ignored.
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.Pp
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The format is required and must be surrounded by double quote
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(" ") marks.
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It is interpreted as a fprintf-style format string (see
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.Xr fprintf 3 ) ,
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with the
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following exceptions:
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.Bl -bullet -offset indent
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.It
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An asterisk (*) may not be used as a field width or precision.
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.It
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A byte count or field precision
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.Em is
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required for each ``s'' conversion
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character (unlike the
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.Xr fprintf 3
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default which prints the entire string if the precision is unspecified).
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.It
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The conversion characters ``h'', ``l'', ``n'', ``p'' and ``q'' are
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not supported.
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.It
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The single character escape sequences
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described in the C standard are supported:
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.Bd -ragged -offset indent -compact
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.Bl -column <alert_character>
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.It "NUL \e0"
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.It "<alert character> \ea"
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.It "<backspace> \eb"
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.It "<form-feed> \ef"
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.It "<newline> \en"
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.It "<carriage return> \er"
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.It "<tab> \et"
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.It "<vertical tab> \ev"
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.El
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.Ed
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.El
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.Pp
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The
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.Nm
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utility also supports the following additional conversion strings:
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.Bl -tag -width Fl
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.It Cm \&_a Ns Op Cm dox
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Display the input offset, cumulative across input files, of the
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next byte to be displayed.
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The appended characters
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.Cm d ,
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.Cm o ,
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and
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.Cm x
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specify the display base
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as decimal, octal or hexadecimal respectively.
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.It Cm \&_A Ns Op Cm dox
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Identical to the
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.Cm \&_a
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conversion string except that it is only performed
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once, when all of the input data has been processed.
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.It Cm \&_c
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Output characters in the default character set.
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Nonprinting characters are displayed in three character, zero-padded
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octal, except for those representable by standard escape notation
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(see above),
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which are displayed as two character strings.
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.It Cm _p
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Output characters in the default character set.
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Nonprinting characters are displayed as a single
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.Dq Cm \&. .
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.It Cm _u
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Output US ASCII
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characters, with the exception that control characters are
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displayed using the following, lower-case, names.
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Characters greater than 0xff, hexadecimal, are displayed as hexadecimal
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strings.
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.Bl -column 000_nu 001_so 002_st 003_et 004_eo
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.It "000 NUL" Ta "001 SOH" Ta "002 STX" Ta "003 ETX" Ta "004 EOT" Ta "005 ENQ"
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.It "006 ACK" Ta "007 BEL" Ta "008 BS" Ta "009 HT" Ta "00A LF" Ta "00B VT"
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.It "00C FF" Ta "00D CR" Ta "00E\ SO" Ta "00F SI" Ta "010 DLE" Ta "011 DC1"
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.It "012 DC2" Ta "013 DC3" Ta "014 DC4" Ta "015\ NAK" Ta "016 SYN" Ta "017 ETB"
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.It "018 CAN" Ta "019 EM" Ta "01A SUB" Ta "01B ESC" Ta "01C FS" Ta "01D GS"
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.It "01E RS" Ta "01F US" Ta "07F DEL" Ta \& Ta \& Ta \&
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.El
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.El
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.Pp
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The default and supported byte counts for the conversion characters
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are as follows:
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.Bl -tag -width "Xc,_Xc,_Xc,_Xc,_Xc,_Xc" -offset indent
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.It Li \&%_c , \&%_p , \&%_u , \&%c
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One byte counts only.
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.It Xo
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.Li \&%d , \&%i , \&%o ,
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.Li \&%u , \&%X , \&%x
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.Xc
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Four byte default, one, two and four byte counts supported.
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.It Xo
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.Li \&%E , \&%e , \&%f ,
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.Li \&%G , \&%g
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.Xc
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Eight byte default, four and twelve byte counts supported.
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.El
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.Pp
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The amount of data interpreted by each format string is the sum of the
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data required by each format unit, which is the iteration count times the
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byte count, or the iteration count times the number of bytes required by
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the format if the byte count is not specified.
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.Pp
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The input is manipulated in ``blocks'', where a block is defined as the
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largest amount of data specified by any format string.
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Format strings interpreting less than an input block's worth of data,
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whose last format unit both interprets some number of bytes and does
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not have a specified iteration count, have the iteration count
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incremented until the entire input block has been processed or there
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is not enough data remaining in the block to satisfy the format string.
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.Pp
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If, either as a result of user specification or
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.Nm
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modifying
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the iteration count as described above, an iteration count is
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greater than one, no trailing whitespace characters are output
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during the last iteration.
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.Pp
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It is an error to specify a byte count as well as multiple conversion
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characters or strings unless all but one of the conversion characters
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or strings is
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.Cm \&_a
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or
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.Cm \&_A .
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.Pp
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If, as a result of the specification of the
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.Fl n
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option or end-of-file being reached, input data only partially
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satisfies a format string, the input block is zero-padded sufficiently
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to display all available data (i.e., any format units overlapping the
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end of data will display some number of the zero bytes).
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.Pp
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Further output by such format strings is replaced by an equivalent
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number of spaces.
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An equivalent number of spaces is defined as the number of spaces
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output by an
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.Cm s
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conversion character with the same field width
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and precision as the original conversion character or conversion
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string but with any
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.Dq Li \&+ ,
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.Dq \&\ \& ,
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.Dq Li \&#
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conversion flag characters
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removed, and referencing a NULL string.
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.Pp
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If no format strings are specified, the default display is equivalent
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to specifying the
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.Fl x
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option.
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.Sh EXIT STATUS
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.Ex -std hexdump hd
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.Sh EXAMPLES
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Dump input in canonical (hex+ASCII) form:
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.Bd -literal -offset indent
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$ echo "FreeBSD: The power to serve" | hexdump -C
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00000000 46 72 65 65 42 53 44 3a 20 54 68 65 20 70 6f 77 |FreeBSD: The pow|
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00000010 65 72 20 74 6f 20 73 65 72 76 65 0a |er to serve.|
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0000001c
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.Ed
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.Pp
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Same as above but skipping the first 4 bytes of stdin and interpreting only 3
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bytes of input:
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.Bd -literal -offset indent
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$ echo "FreeBSD: The power to serve" | hexdump -C -s 4 -n 3
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00000004 42 53 44 |BSD|
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00000007
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.Ed
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.Pp
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Assuming a format file named
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.Pa format.txt
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with the following contents that specify a perusal format:
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.Bd -literal -offset indent
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"%06.6_ao " 12/1 "%3_u "
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"\et\et" "%_p "
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"\en"
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.Ed
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.Pp
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Dump input in canonical form using the format in
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.Pa format.txt :
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.Bd -literal -offset indent
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$ echo "FreeBSD" | hexdump -f format.txt -C
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000000 F r e e B S D lf F r e e B S D .
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00000000 46 72 65 65 42 53 44 0a |FreeBSD.|
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00000008
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.Ed
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.Pp
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Assuming a format file named
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.Pa format.txt
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with the following contents that simulate the
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.Fl x
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option:
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.Bd -literal -offset indent
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"%07.7_Ax\en"
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"%07.7_ax " 8/2 "%04x " "\en"
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.Ed
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.Pp
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Dump input in canonical form using the format in
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.Pa format.txt :
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.Bd -literal -offset indent
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$ echo "FreeBSD: The power to serve" | hexdump -f format.txt -C
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0000000 7246 6565 5342 3a44 5420 6568 7020 776f
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00000000 46 72 65 65 42 53 44 3a 20 54 68 65 20 70 6f 77 |FreeBSD: The pow|
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0000010 7265 7420 206f 6573 7672 0a65
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00000010 65 72 20 74 6f 20 73 65 72 76 65 0a |er to serve.|
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0000001c
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.Ed
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.Sh SEE ALSO
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.Xr od 1
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