NAME
hexdump, hd - ASCII, decimal, hexadecimal, octal dump
SYNOPSIS
hexdump [-bcCdovx] [-e format_string] [-f format_file] [-n length]
[-s skip] file ...
hd [-bcdovx] [-e format_string] [-f format_file] [-n length] [-s skip]
file ...
DESCRIPTION
The hexdump utility is a filter which displays the specified files, or
the standard input, if no files are specified, in a user specified
format.
The options are as follows:
-b 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.
-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 line.
-C 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.
-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.
-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 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 hexadecimal,
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. 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 512, 1024, or 1048576, respectively.
-v 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.
-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, 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:
· An asterisk (*) may not be used as a field width or precision.
· 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:
NUL \0
<alert character> \a
<backspace> \b
<form-feed> \f
<newline> \n
<carriage return> \r
<tab> \t
<vertical tab> \v
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
The default and supported byte counts for the conversion characters are
as follows:
%_c, %_p, %_u, %c One byte counts only.
%u, %X, %x’ Four byte default, one, two and
four byte counts supported.
%G, %g’ %f, Eight byte default, four and twelve
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 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 equivalent to
specifying the -x option.
EXIT STATUS
The hexdump and hd utilities exit 0 on success, and >0 if an error
occurs.
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"
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"’
68
65
6C
6C
6F
0A
# 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"’
0# _h_
1# _e_
2# _l_
3# _l_
4# _o_
5# _lf_
SEE ALSO
gdb(1), od(1)