HEXDUMP(1) User Commands HEXDUMP(1)
hexdump - display file contents in ascii, decimal, hexadecimal, or octal
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.
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 hexadecimal, followed by six-
teen space-separated, three-column, zero-filled bytes of input data, in octal, per
-c One-byte character display. Display the input offset in hexadecimal, followed by
sixteen space-separated, three-column, space-filled characters of input data per
-C Canonical hex+ASCII display. Display the input offset in hexadecimal, followed by
sixteen space-separated, two-column, hexadecimal bytes, followed by the same six-
teen bytes in %_p format enclosed in '|' characters.
-d 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.
Specify a format string to be used for displaying data.
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.
Interpret only length bytes of input.
-o 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.
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 pre-
ceding group of output lines (except for the input offsets), are replaced with a
line comprised of a single asterisk.
-x 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.
For each input file, hexdump sequentially copies the input to standard output, transform-
ing 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 white-
space before or after the slash is ignored.
The format is required and must be surrounded by double quote (" ") marks. It is inter-
preted 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 unspeci-
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:
<alert character> \a
<carriage return> \r
<vertical tab> \v
The hexdump utility also supports the following additional conversion strings.
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 deci-
mal, octal or hexadecimal respectively.
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 dis-
played 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 dis-
played as a single '.'.
_u Output US ASCII characters, with the exception that control characters are dis-
played using the following, lower-case, names. Characters greater than 0xff, hexa-
decimal, 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
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 sat-
isfy 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 dis-
play 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 ref-
erencing a NULL string.
If no format strings are specified, the default display is equivalent to specifying the -x
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 "
Implement the -x option:
"%07.7_ax " 8/2 "%04x " "\n"
The hexdump utility is expected to be IEEE Std 1003.2 ("POSIX.2") compatible.
The hexdump command is part of the util-linux package and is available from Linux Kernel
util-linux September 2011 HEXDUMP(1)