NAME
hexdump —
ascii, decimal, hexadecimal,
octal dump
SYNOPSIS
hexdump |
[-bCcdovx]
[-e
format_string]
[-f
format_file]
[-n
length]
[-s skip]
[file ...] |
DESCRIPTION
The
hexdump utility is a filter which displays each specified
file, or the standard input if no
file arguments 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
- 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.
-
-
- -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.
-
-
- -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
skip
- Skip skip bytes from the beginning of
the input. By default, skip is interpreted as a
decimal number. With a leading 0x or
0X, skip is interpreted as a
hexadecimal number; otherwise, with a leading 0,
skip is interpreted as an octal number. Appending
the character b, k, or
m to skip causes it to be
interpreted as a multiple of
512
,
1024
, or 1048576
,
respectively.
-
-
- -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 containing 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.
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 |
hexdump 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.
Non-printing 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.
Non-printing 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 |
07F 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, four and eight 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 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 ‘
+
’, ‘ ’,
and ‘
#
’ 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 utility exits 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"
SEE ALSO
od(1)