HEXDUMP
Section: User Commands (1)
Updated: April 2013
Page Index
NAME
hexdump - display file contents in hexadecimal, decimal, octal, or ascii
SYNOPSIS
hexdump
[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.
- -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.
- -V, --version
-
Display version information and exit.
- -h, --help
-
Display help text 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]
-
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\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
Implicit coloring can be disabled by an empty file
/etc/terminal-colors.d/hexdump.disable.
See
terminal-colors.d(5)
for more details about colorization configuration.
AVAILABILITY
The hexdump command is part of the util-linux package and is available from
Linux Kernel Archive