hd(1)

NAME#

hexdump - display file contents in hexadecimal, decimal, octal, or ascii

SYNOPSIS#

hexdumpoptions file ...

hdoptions 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

-X, --one-byte-hex

-c, --one-byte-char

-C, --canonical

-d, --two-bytes-decimal

-e, --formatformat_string

-f, --format-filefile

-L, --color[=when]

-n, --lengthlength

-o, --two-bytes-octal

-s, --skipoffset

-v, --no-squeezing

-x, --two-bytes-hex

-h, --help

-V, --version

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.

2.

3.

4.

Conversion strings#

The hexdump utility also supports the following additional conversion strings.

_a[dox]

_A[dox]

_c

_p

_u

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]]

!

COLOR

VALUE

OFFSET

Counters#

The default and supported byte counts for the conversion characters are as follows:

%_c, %_p, %_u, %c

%d, %i, %o, %u, %X, %x

%E, %e, %f, %G, %g

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:

\n
   "%06.6_ao "  12/1 "%3_u "
\n
   "\t" "%_p "
\n
   "\n"

Implement the -x option:

\n
   "%07.7_Ax\n"
\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.

\n
   "%07.7_Ax_L[cyan]\n"
\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

Since version 2.41, the $NO_COLOR environment variable is also supported to disable output colorization unless explicitly enabled by a command-line option.

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 <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/>.