HEXDUMP("1") manual page
Table of Contents
hexdump - display file contents in
hexadecimal, decimal, octal, or ascii
hexdump [options] file...
The
hexdump utility is a filter which displays the specified files, or standard
input if no files are specified, in a user-specified format.
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.
- -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 (enabled by default). The
optional argument when can be auto, never or always. If the when argument
is omitted, then it defaults to auto.
- -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.
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:
.- An asterisk (*) may not be used as a field width or precision.
.- 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).
.- The conversion characters h, l, n, p, and q are not supported.
.- 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
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. 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.
- _p
- Output characters in the default character set. Nonprinting
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 |
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.
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
equivalent to specifying the -x option.
hexdump exits 0 on success
and >0 if an error occurred.
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"
ColorsImplicit 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.
StandardsThe hexdump utility is expected to be IEEE Std 1003.2 ("POSIX.2")
compatible. AvailabilityThe hexdump command is part of the util-linux package
and is available from Linux Kernel Archive
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