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XXD(1)											   XXD(1)

NAME
       xxd - make a hexdump or do the reverse.

SYNOPSIS
       xxd -h[elp]
       xxd [options] [infile [outfile]]
       xxd -r[evert] [options] [infile [outfile]]

DESCRIPTION
       xxd  creates a hex dump of a given file or standard input.  It can also convert a hex dump
       back to its original binary form.  Like uuencode(1) and uudecode(1) it allows  the  trans-
       mission	of  binary  data  in a `mail-safe' ASCII representation, but has the advantage of
       decoding to standard output.  Moreover, it can be used to perform binary file patching.

OPTIONS
       If no infile is given, standard input is read.  If infile is specified as a `-' character,
       then input is taken from standard input.  If no outfile is given (or a `-' character is in
       its place), results are sent to standard output.

       Note that a "lazy" parser is used which does not check for more than the first option let-
       ter,  unless the option is followed by a parameter.  Spaces between a single option letter
       and its parameter are optional.	Parameters to options can be specified in decimal,  hexa-
       decimal or octal notation.  Thus -c8, -c 8, -c 010 and -cols 8 are all equivalent.

       -a | -autoskip
	      toggle autoskip: A single '*' replaces nul-lines.  Default off.

       -b | -bits
	      Switch  to  bits	(binary  digits)  dump,  rather than hexdump.  This option writes
	      octets as eight digits "1"s and "0"s instead of a  normal  hexacecimal  dump.  Each
	      line  is	preceded  by  a  line  number in hexadecimal and followed by an ascii (or
	      ebcdic) representation. The command line switches -r, -p, -i do not work with  this
	      mode.

       -c cols | -cols cols
	      -c  cols	|  -cols cols format <cols> octets per line. Default 16 (-i: 12, -ps: 30,
	      -b: 6). Max 256.

       -E | -EBCDIC
	      Change the character encoding in the righthand column from ASCII to  EBCDIC.   This
	      does not change the hexadecimal representation. The option is meaningless in combi-
	      nations with -r, -p or -i.

       -g bytes | -groupsize bytes
	      seperate the output of every <bytes> bytes (two hex characters or eight  bit-digits
	      each)  by  a whitespace.	Specify -g 0 to suppress grouping.  <Bytes> defaults to 2
	      in normal mode and 1 in bits mode.   Grouping  does  not	apply  to  postscript  or
	      include style.

       -h | -help
	      print a summary of available commands and exit.  No hex dumping is performed.

       -i | -include
	      output  in  C  include  file  style.  A complete static array definition is written
	      (named after the input file), unless xxd reads from stdin.

       -l len | -len len
	      stop after writing <len> octets.

       -p | -ps | -postscript | -plain
	      output in postscript continuous hexdump style. Also known as plain hexdump style.

       -r | -revert
	      reverse operation: convert (or patch) hexdump into binary.  If not writing to  std-
	      out,  xxd writes into its output file without truncating it. Use the combination -r
	      -p to read plain hexadecimal dumps without line number information  and  without	a
	      particular  column  layout.  Additional Whitespace and line-breaks are allowed any-
	      where.

       -seek offset
	      When used after -r : revert with <offset> added to file positions found in hexdump.

       -s [+][-]seek
	      start at <seek> bytes abs. (or rel.) infile offset.  + indicates that the  seek  is
	      relative	to  the  current  stdin  file position (meaningless when not reading from
	      stdin).  - indicates that the seek should be that many characters from the  end  of
	      the input (or if combined with
	       + : before the current stdin file position).  Without -s option, xxd starts at the
	      current file position.

       -u     use upper case hex letters. Default is lower case.

       -v | -version
	      show version string.

CAVEATS
       xxd -r has some builtin magic while evaluating line number information.	If the ouput file
       is  seekable,  then the linenumbers at the start of each hexdump line may be out of order,
       lines may be missing, or overlapping. In these cases xxd will lseek(2) to the  next  posi-
       tion.  If  the output file is not seekable, only gaps are allowed, which will be filled by
       null-bytes.

       xxd -r never generates parse errors. Garbage is silently skipped.

       When editing hexdumps, please note that xxd -r skips everything on the  input  line  after
       reading	enough columns of hexadecimal data (see option -c). This also means, that changes
       to the printable ascii (or ebcdic) columns are always ignored. Reverting a plain (or post-
       script)	style  hexdump	with  xxd -r -p does not depend on the correct number of columns.
       Here an thing that looks like a pair of hex-digits is interpreted.

       Note the difference between
       % xxd -i file
       and
       % xxd -i < file

       xxd -s +seek may be different from xxd -s seek , as lseek(2) is used to "rewind" input.	A
       '+'  makes  a difference if the input source is stdin, and if stdin's file position is not
       at the start of the file by the time xxd is started and given its  input.   The	following
       examples may help to clarify (or further confuse!)...

       Rewind  stdin  before  reading;	needed	because  the `cat' has already read to the end of
       stdin.
       % sh -c 'cat > plain_copy; xxd -s 0 > hex_copy' < file

       Hexdump from file position 0x480 (=1024+128) onwards.  The `+' sign means "relative to the
       current position", thus the `128' adds to the 1k where dd left off.
       % sh -c 'dd of=plain_snippet bs=1k count=1; xxd -s +128 > hex_snippet' < file

       Hexdump from file position 0x100 ( = 1024-768) on.
       % sh -c 'dd of=plain_snippet bs=1k count=1; xxd -s +-768 > hex_snippet' < file

       However, this is a rare situation and the use of `+' is rarely needed.  the author prefers
       to monitor the effect of xxd with strace(1) or truss(1), whenever -s is used.

EXAMPLES
       Print everything but the first three lines (hex 0x30 bytes) of file
       % xxd -s 0x30 file

       Print 3 lines (hex 0x30 bytes) from the end of file
       % xxd -s -0x30 file

       Print 120 bytes as continuous hexdump with 40 octets per line.
       % xxd -l 120 -ps -c 20 xxd.1
       2e544820585844203120224d616e75616c207061
       676520666f7220787864220a2e5c220a2e5c2220
       32317374204d617920313939360a2e5c22204d61
       6e207061676520617574686f723a0a2e5c222020
       2020546f6e79204e7567656e74203c746f6e7940
       7363746e7567656e2e7070702e67752e6564752e

       Hexdump the first 120 bytes of this man page with 12 octets per line.
       % xxd -l 120 -c 12 xxd.1
       0000000: 2e54 4820 5858 4420 3120 224d  .TH XXD 1 "M
       000000c: 616e 7561 6c20 7061 6765 2066  anual page f
       0000018: 6f72 2078 7864 220a 2e5c 220a  or xxd"..\".
       0000024: 2e5c 2220 3231 7374 204d 6179  .\" 21st May
       0000030: 2031 3939 360a 2e5c 2220 4d61	1996..\" Ma
       000003c: 6e20 7061 6765 2061 7574 686f  n page autho
       0000048: 723a 0a2e 5c22 2020 2020 546f  r:..\"	 To
       0000054: 6e79 204e 7567 656e 7420 3c74  ny Nugent <t
       0000060: 6f6e 7940 7363 746e 7567 656e  ony@sctnugen
       000006c: 2e70 7070 2e67 752e 6564 752e  .ppp.gu.edu.

       Display just the date from the file xxd.1
       % xxd -s 0x28 -l 12 -c 12 xxd.1
       0000028: 3231 7374 204d 6179 2031 3939  21st May 199

       Copy input_file to output_file and prepend 100 bytes of value 0x00.
       % xxd input_file | xxd -r -s 100 > output_file

       Patch the date in the file xxd.1
       % echo '0000029: 3574 68' | xxd -r - xxd.1
       % xxd -s 0x28 -l 12 -c 12 xxd.1
       0000028: 3235 7468 204d 6179 2031 3939  25th May 199

       Create a 65537 byte file with all bytes 0x00, except for the last one which  is	'A'  (hex
       0x41).
       % echo '010000: 41' | xxd -r > file

       Hexdump this file with autoskip.
       % xxd -a -c 12 file
       0000000: 0000 0000 0000 0000 0000 0000  ............
       *
       000fffc: 0000 0000 40		       ....A

       Create  a 1 byte file containing a single 'A' character.  The number after '-r -s' adds to
       the linenumbers found in the file; in effect, the leading bytes are suppressed.
       % echo '010000: 41' | xxd -r -s -0x10000 > file

       Use xxd as a filter within an editor such as vim(1) to hexdump a region marked between `a'
       and `z'.
       :'a,'z!xxd

       Use  xxd  as  a	filter within an editor such as vim(1) to recover a binary hexdump marked
       between `a' and `z'.
       :'a,'z!xxd -r

       Use xxd as a filter within an editor such as vim(1) to recover  one  line  of  a  hexdump.
       Move the cursor over the line and type:
       !!xxd -r

       Read single characters from a serial line
       % xxd -c1 < /dev/term/b &
       % stty < /dev/term/b -echo -opost -isig -icanon min 1
       % echo -n foo > /dev/term/b

RETURN VALUES
       The following error values are returned:

       0      no errors encountered.

       -1     operation not supported ( xxd -r -i still impossible).

       1      error while parsing options.

       2      problems with input file.

       3      problems with output file.

       4,5    desired seek position is unreachable.

SEE ALSO
       uuencode(1), uudecode(1), patch(1)

WARNINGS
       The  tools  weirdness  matches  its  creators  brain.  Use entirely at your own risk. Copy
       files. Trace it. Become a wizard.

VERSION
       This manual page documents xxd version 1.7

AUTHOR
       (c) 1990-1997 by Juergen Weigert
       <jnweiger@informatik.uni-erlangen.de>

       Distribute freely and credit me,
       make money and share with me,
       lose money and don't ask me.

       Manual page started by Tony Nugent
       <tony@sctnugen.ppp.gu.edu.au> <T.Nugent@sct.gu.edu.au>
       Small changes by Bram Moolenaar.  Edited by Juergen Weigert.

Manual page for xxd			   August 1996					   XXD(1)
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