xxd



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 representation, but has the advantage of decoding to  stan-
       dard 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 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  hexadecimal and followed by an ascii (or ebcdic) representa-
              tion. 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 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 whitespace.  Specify -g 0 to sup-
              press 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 defini-
              tion 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 combination -r -p to read plain hexadeci-
              mal dumps without line number information and without a particu-
              lar column layout. Additional  Whitespace  and  line-breaks  are
              allowed anywhere.

       -seek offset
              When  used  after  -r : revert with <offset> added to file posi-
              tions 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 over-
       lapping. In these cases xxd will lseek(2) to the next position. 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 postscript) 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 inter-
       preted.

       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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