hexdump - display file contents in hexadecimal, decimal, octal, or ascii
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
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
- -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 (#)
- -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
- -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
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
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
, 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
- <alert character>
- <carriage return>
- <vertical tab>
utility also supports the following additional conversion
- 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
- Identical to the _a conversion string except that it is only
performed once, when all of the input data has been processed.
- 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.
- Output characters in the default character set. Non-printing characters
are displayed as a single '.'.
- 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.
When put at the end of a format specifier, hexdump highlights the respective
string with the color specified. Conditions, if present, are evaluated prior
The full syntax of a color unit is as follows:
- 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.
- One of the 8 basic shell colors.
- 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.
- 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
- %_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
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
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
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
', ´ ´, '#
' conversion flag characters
removed, and referencing a NULL string.
If no format strings are specified, the default display is very similar to the
output format (the -x
option causes more space to be used
between format units than in the default output).
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 "
Implement the -x option:
"%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] " 8/2 " %04x_L[green:0xAA55@510-511,!red:0xAA55@510-511] " "\n"
Implicit coloring can be disabled by an empty file
for more details about colorization
utility is expected to be IEEE Std 1003.2
The hexdump command is part of the util-linux package and is available from