HEXDUMP(1) BSD General Commands Manual HEXDUMP(1)NAMEhexdump — ascii, decimal, hexadecimal, octal dump
SYNOPSIShexdump [-bcdovx] [-e format_string] [-f format_file] [-n length]
[-s skip] file ...
The hexdump utility is a filter which displays the specified files, or
the standard input, if no files are specified, in a user specified for‐
The options are as follows:
-b One-byte octal display. Display the input offset in hexadec‐
imal, 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
hexadecimal, followed by sixteen space-separated, three col‐
umn, space-filled, characters of input data per line.
-d Two-byte decimal display. Display the input offset in hexa‐
decimal, followed by eight space-separated, five column,
zero-filled, two-byte units of input data, in unsigned deci‐
mal, 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.
-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
-s offset Skip offset bytes from the beginning of the input. By
default, offset is interpreted as a decimal number. With a
leading 0x or 0X, offset is interpreted as a hexadecimal num‐
ber, otherwise, with a leading 0, offset is interpreted as an
octal number. Appending the character b, k, or m to offset
causes it to be interpreted as a multiple of 512, 1024, or
-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 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 hexadeci‐
mal, 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.
A format string contains any number of format units, separated by white‐
space. 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'' con‐
version 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 stan‐
dard are supported:
<alert character> \a
<carriage return> \r
<vertical tab> \v
Hexdump also supports the 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 hexadeci‐
_A[dox] Identical to the _a conversion string except that it is only
performed once, when all of the input data has been pro‐
_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
_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 dis‐
played 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
%_c, %_p, %_u, %c One byte counts only.
%d, %i, %o, %u, %X, %x Four byte default, one, two and four byte
%E, %e, %f, %G, %g Eight byte default, four byte counts sup‐
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 itera‐
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 num‐
ber 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 referenc‐
ing 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 "
Implement the -x option:
"%07.7_ax " 8/2 "%04x " "\n"
SEE ALSOadb(1)BSD April 18, 1994 BSD