HEXDUMP(1) User Commands HEXDUMP(1)
NAME
hexdump - display file contents in ascii, decimal, hexadecimal, or
octal
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
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 display. Display the input offset in hexadeci-
mal, followed by sixteen space-separated, three-column, zero-
filled bytes of input data, in octal, per line.
-c One-byte character display. Display the input offset in hexa-
decimal, followed by sixteen space-separated, three-column,
space-filled characters of input data per line.
-C Canonical hex+ASCII display. Display the input offset in hexa-
decimal, followed by sixteen space-separated, two-column, hexa-
decimal bytes, followed by the same sixteen bytes in %_p format
enclosed in '|' characters.
-d Two-byte decimal display. Display the input offset in hexadeci-
mal, followed by eight space-separated, five-column, zero-
filled, two-byte units of input data, in unsigned decimal, per
line.
-e format_string
Specify a format string to be used for displaying data.
-f format_file
Specify a file that contains one or more newline separated for-
mat strings. Empty lines and lines whose first non-blank char-
acter is a hash mark (#) are ignored.
-n length
Interpret only length bytes of input.
-o Two-byte octal display. Display the input offset in hexadeci-
mal, followed by eight space-separated, six-column, zero-filled,
two-byte quantities of input data, in octal, per line.
-s offset
Skip offset bytes from the beginning of the input.
-v 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 com-
prised of a single asterisk.
-x Two-byte hexadecimal display. Display the input offset in hexa-
decimal, followed by eight space-separated, four-column, zero-
filled, two-byte quantities of input data, in hexadecimal, per
line.
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 conver-
sion 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 stan-
dard 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. 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
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 for-
mat unit both interprets some number of bytes and does not have a spec-
ified 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 iter-
ation.
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 num-
ber 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 ref-
erencing a NULL string.
If no format strings are specified, the default display is equivalent
to specifying the -x option.
EXIT STATUS
hexdump exits 0 on success and >0 if an error occurred.
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"
STANDARDS
The hexdump utility is expected to be IEEE Std 1003.2 ("POSIX.2") com-
patible.
AVAILABILITY
The hexdump command is part of the util-linux package and is available
from Linux Kernel Archive <ftp://ftp.kernel.org/pub/linux/utils/util-
linux/>.
util-linux September 2011 HEXDUMP(1)
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