runtime/doc/xxd.man

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.



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XXD(1)                                                     XXD(1)


       -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.





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XXD(1)                                                     XXD(1)


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



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XXD(1)                                                     XXD(1)


       % 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



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XXD(1)                                                     XXD(1)


       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,



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XXD(1)                                                     XXD(1)


       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.


















































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