Provided by: bsdextrautils_2.40.2-1ubuntu2_amd64 
NAME
hexdump - display file contents in hexadecimal, decimal, octal, or ascii
SYNOPSIS
hexdump options file ...
hd options file ...
DESCRIPTION
The hexdump utility is a filter which displays the specified files, or standard input if
no files are specified, in a user-specified format.
OPTIONS
Below, the length and offset arguments may be followed by the multiplicative suffixes KiB
(=1024), MiB (=1024*1024), and so on for GiB, TiB, PiB, EiB, ZiB and YiB (the "iB" is
optional, e.g., "K" has the same meaning as "KiB"), or the suffixes KB (=1000), MB
(=1000*1000), and so on for GB, TB, PB, EB, ZB and YB.
-b, --one-byte-octal
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.
-X, --one-byte-hex
One-byte hexadecimal display. Display the input offset in hexadecimal, followed by
sixteen space-separated, two-column, zero-filled bytes of input data, in hexadecimal,
per line.
-c, --one-byte-char
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.
-C, --canonical
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. Invoking the program as hd implies this
option.
-d, --two-bytes-decimal
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.
-e, --format format_string
Specify a format string to be used for displaying data.
-f, --format-file 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 (#) are ignored.
-L, --color[=when]
Accept color units for the output. The optional argument when can be auto, never or
always. If the when argument is omitted, it defaults to auto. The colors can be
disabled; for the current built-in default see the --help output. See also the Colors
subsection and the COLORS section below.
-n, --length length
Interpret only length bytes of input.
-o, --two-bytes-octal
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.
-s, --skip offset
Skip offset bytes from the beginning of the input.
-v, --no-squeezing
The -v option causes hexdump to display all input data. Without the -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.
-x, --two-bytes-hex
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.
-h, --help
Display help text and exit.
-V, --version
Print version and exit.
For each input file, hexdump sequentially copies the input to standard output,
transforming the data according to the format strings specified by the -e and -f options,
in the order that they were specified.
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.
The iteration count is an optional positive integer, which defaults to one. Each format is
applied iteration count times.
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.
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.
The format is required and must be surrounded by double quote (" ") marks. It is
interpreted as a fprintf-style format string (see fprintf(3)), with the following
exceptions:
1.
An asterisk (*) may not be used as a field width or precision.
2.
A byte count or field precision is required for each s conversion character (unlike
the fprintf(3) default which prints the entire string if the precision is
unspecified).
3.
The conversion characters h, l, n, p, and q are not supported.
4.
The single character escape sequences described in the C standard are supported:
┌──────────────────┬────┐
│ │ │
│NULL │ \0 │
├──────────────────┼────┤
│ │ │
│<alert character> │ \a │
├──────────────────┼────┤
│ │ │
│<backspace> │ \b │
├──────────────────┼────┤
│ │ │
│<form-feed> │ \f │
├──────────────────┼────┤
│ │ │
│<newline> │ \n │
├──────────────────┼────┤
│ │ │
│<carriage return> │ \r │
├──────────────────┼────┤
│ │ │
│<tab> │ \t │
├──────────────────┼────┤
│ │ │
│<vertical tab> │ \v │
└──────────────────┴────┘
Conversion strings
The hexdump utility also supports the following additional conversion strings.
_a[dox]
Display the input offset, cumulative across input files, of the next byte to be
displayed. The appended characters d, o, and x specify the display base as
decimal, octal or hexadecimal respectively.
_A[dox]
Almost identical to the _a conversion string except that it is only performed
once, when all of the input data has been processed.
_c
Output characters in the default character set. Non-printing 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.
_p
Output characters in the default character set. Non-printing characters are
displayed as a single '.'.
_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.
┌────────┬─────────┬─────────┬─────────┬─────────┬─────────┐
│ │ │ │ │ │ │
│000 nul │ 001 soh │ 002 stx │ 003 etx │ 004 eot │ 005 enq │
├────────┼─────────┼─────────┼─────────┼─────────┼─────────┤
│ │ │ │ │ │ │
│006 ack │ 007 bel │ 008 bs │ 009 ht │ 00A lf │ 00B vt │
├────────┼─────────┼─────────┼─────────┼─────────┼─────────┤
│ │ │ │ │ │ │
│00C ff │ 00D cr │ 00E so │ 00F si │ 010 dle │ 011 dc1 │
├────────┼─────────┼─────────┼─────────┼─────────┼─────────┤
│ │ │ │ │ │ │
│012 dc2 │ 013 dc3 │ 014 dc4 │ 015 nak │ 016 syn │ 017 etb │
├────────┼─────────┼─────────┼─────────┼─────────┼─────────┤
│ │ │ │ │ │ │
│018 can │ 019 em │ 01A sub │ 01B esc │ 01C fs │ 01D gs │
├────────┼─────────┼─────────┼─────────┼─────────┼─────────┤
│ │ │ │ │ │ │
│01E rs │ 01F us │ 0FF del │ │ │ │
└────────┴─────────┴─────────┴─────────┴─────────┴─────────┘
Colors
When put at the end of a format specifier, hexdump highlights the respective
string with the color specified. Conditions, if present, are evaluated prior
to highlighting.
_L[color_unit_1,color_unit_2,...,color_unit_n]
The full syntax of a color unit is as follows:
[!]COLOR[:VALUE][@OFFSET_START[-END]]
!
Negate the condition. Please note that it only makes sense to negate a
unit if both a value/string and an offset are specified. In that case the
respective output string will be highlighted if and only if the
value/string does not match the one at the offset.
COLOR
One of the 8 basic shell colors.
VALUE
A value to be matched specified in hexadecimal, or octal base, or as a
string. Please note that the usual C escape sequences are not interpreted
by hexdump inside the color_units.
OFFSET
An offset or an offset range at which to check for a match. Please note
that lone OFFSET_START uses the same value as END offset.
Counters
The default and supported byte counts for the conversion characters are as
follows:
%_c, %_p, %_u, %c
One byte counts only.
%d, %i, %o, %u, %X, %x
Four byte default, one, two and four byte counts supported.
%E, %e, %f, %G, %g
Eight byte default, four byte counts supported.
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.
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.
If, either as a result of user specification or hexdump modifying the
iteration count as described above, an iteration count is greater than one, no
trailing whitespace characters are output during the last iteration.
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 _a or _A.
If, as a result of the specification of the -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).
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 s conversion character with the same field width and precision as
the original conversion character or conversion string but with any '+', ' ',
'#' conversion flag characters removed, and referencing a NULL string.
If no format strings are specified, the default display is very similar to the
-x output format (the -x option causes more space to be used between format
units than in the default output).
EXIT STATUS
hexdump exits 0 on success and > 0 if an error occurred.
CONFORMING TO
The hexdump utility is expected to be IEEE Std 1003.2 ("POSIX.2") compatible.
EXAMPLES
Display the input in perusal format:
"%06.6_ao " 12/1 "%3_u "
"\t" "%_p "
"\n"
Implement the -x option:
"%07.7_Ax\n"
"%07.7_ax " 8/2 "%04x " "\n"
MBR Boot Signature example: Highlight the addresses cyan and the bytes at
offsets 510 and 511 green if their value is 0xAA55, red otherwise.
"%07.7_Ax_L[cyan]\n"
"%07.7_ax_L[cyan] " 8/2 " %04x_L[green:0xAA55@510-511,!red:0xAA55@510-511] " "\n"
COLORS
The output colorization is implemented by terminal-colors.d(5) functionality.
Implicit coloring can be disabled by an empty file
/etc/terminal-colors.d/hexdump.disable
for the hexdump command or for all tools by
/etc/terminal-colors.d/disable
The user-specific $XDG_CONFIG_HOME/terminal-colors.d or
$HOME/.config/terminal-colors.d overrides the global setting.
Note that the output colorization may be enabled by default, and in this case
terminal-colors.d directories do not have to exist yet.
REPORTING BUGS
For bug reports, use the issue tracker at
https://github.com/util-linux/util-linux/issues.
AVAILABILITY
The hexdump command is part of the util-linux package which can be downloaded
from Linux Kernel Archive
<https://www.kernel.org/pub/linux/utils/util-linux/>.