decimal, hexadecimal, octal dump
utility is a filter which displays the specified
files, or the standard input, if no files are specified, in a user specified
The options are as follows:
- 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.
- 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.
- 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 ``|'' characters.
Calling the command hd implies this option.
- 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,
- Specify a format string to be used for displaying
- 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
- 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. By default, offset is interpreted as a
decimal number. With a leading 0x or
0X, offset is interpreted as a
hexadecimal number, 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
- Cause 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.
- 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,
For each input file, hexdump
sequentially copies the input to
standard output, transforming the data according to the format strings
specified by the -e
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
- 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 supported:
utility also supports the following additional
- 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.
- Identical to the _a conversion string
except that it is only performed once, when all of the input data has been
- 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.
- Output characters in the default character set. Nonprinting
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
|000 NUL001 SOH002 STX003 ETX004 EOT005 ENQ
|006 ACK007 BEL008 BS009 HT00A LF00B VT
|00C FF00D CR00E SO00F SI010 DLE011 DC1
|012 DC2013 DC3014 DC4015 NAK016 SYN017 ETB
|018 CAN019 EM01A SUB01B ESC01C FS01D GS
|01E RS01F US07F DEL
The default and supported byte counts for the conversion characters are as
- One byte counts only.
- Four byte default, one, two and four byte counts
- Eight byte default, four and twelve byte counts
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
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
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
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 equivalent to
specifying the -x
utilities exit 0 on
success, and >0 if an error occurs.
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"
Some examples for the -e option:
# hex bytes
% echo hello | hexdump -v -e '/1 "%02X "' ; echo
68 65 6C 6C 6F 0A
# same, with ASCII section
% echo hello | hexdump -e '8/1 "%02X ""\t"" "' -e '8/1 "%c""\n"'
68 65 6C 6C 6F 0A hello
# hex with preceding 'x'
% echo hello | hexdump -v -e '"x" 1/1 "%02X" " "' ; echo
x68 x65 x6C x6C x6F x0A
# one hex byte per line
% echo hello | hexdump -v -e '/1 "%02X\n"'
# a table of byte#, hex, decimal, octal, ASCII
% echo hello | hexdump -v -e '/1 "%_ad# "' -e '/1 "%02X hex"' -e '/1 " = %03i dec"' -e '/1 " = %03o oct"' -e '/1 " = _%c\_\n"'
0# 68 hex = 104 dec = 150 oct = _h_
1# 65 hex = 101 dec = 145 oct = _e_
2# 6C hex = 108 dec = 154 oct = _l_
3# 6C hex = 108 dec = 154 oct = _l_
4# 6F hex = 111 dec = 157 oct = _o_
5# 0A hex = 010 dec = 012 oct = _
# byte# & ASCII with control chars
% echo hello | hexdump -v -e '/1 "%_ad# "' -e '/1 " _%_u\_\n"'