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
       transmission of binary data in a `mail-safe' ASCII  repre-
       sentation,  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 `-' charac-
       ter 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 letter, 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, hexadecimal 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 hexadeci-
	      mal and followed by an ascii (or ebcdic)	represen-
	      tation. 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 col-
	      umn from ASCII to EBCDIC.	 This does not change the
	      hexadecimal  representation. The option is meaning-
	      less in combinations 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 whites-
	      pace.  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 stdout, xxd writes  into
	      its output file without truncating it. Use the com-
	      bination -r -p  to  read	plain  hexadecimal  dumps
	      without  line number information and without a par-
	      ticular column layout.  Additional  Whitespace  and
	      line-breaks are allowed anywhere.

       -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 cur-
	      rent 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 position. If the  out-
       put  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 postscript) style
       hexdump with xxd -r -p does not depend on the correct num-
       ber  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 differ-
       ence 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 impossi-
	      ble).

       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				6


