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PROGRAM:

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 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 and four byte counts supported.

%E, %e, %f, %G, %g 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_

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