HardenedBSD/usr.bin/hexdump/hexdump.1

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