runtime/doc/xxd.man

XXD(1)                      General Commands Manual                     XXD(1)

NAME
       xxd - make a hex dump 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 hex dump.  This
              option writes octets as eight digits "1"s and "0"s instead of  a
              normal  hexadecimal dump. Each line is preceded by a line number
              in hexadecimal and followed by an ASCII (or EBCDIC)  representa‐
              tion.  The  command line switch -p does not work with this mode.
              Can be combined with -i.

       -c cols | -cols cols
              Format <cols> octets per line. Default 16 (-i: 12, -ps: 30,  -b:
              6).  Max  256.   No  maximum for -ps. With -ps, 0 results in one
              long line of output.

       -C | -capitalize
              Capitalize variable names in C include file  style,  when  using
              -i.

       -d     show offset in decimal instead of hex.

       -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.

       -e     Switch  to  little-endian  hex  dump.   This  option treats byte
              groups as words in little-endian byte order.  The default group‐
              ing of 4 bytes may be changed using -g.  This  option  only  ap‐
              plies to the hex dump, leaving the ASCII (or EBCDIC) representa‐
              tion  unchanged.   The  command  line switches -r, -p, -i do not
              work with this mode.

       -g bytes | -groupsize bytes
              Separate 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, 4 in lit‐
              tle-endian  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. Can be combined with -b.

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

       -n name  |  -name name
              Override  the variable name output when -i is used. The array is
              named name and the length is named name_len.

       -o offset
              Add <offset> to the displayed file position.

       -p | -ps | -postscript | -plain
              Output in PostScript continuous hex dump style.  Also  known  as
              plain hex dump style.

       -r | -revert
              Reverse  operation: convert (or patch) hex dump 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 al‐
              lowed  anywhere.  Use  the combination -r -b to read a bits dump
              instead of a hex dump.

       -R when
              In the output the hex-value and the value are both colored  with
              the  same  color  depending  on the hex-value. Mostly helping to
              differentiate printable and non-printable characters.   when  is
              never,  always, or auto (default: auto).  When the $NO_COLOR en‐
              vironment variable is set, colorization will be disabled.

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

       -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 built-in magic while evaluating  line  number  informa‐
       tion.   If  the  output  file is seekable, then the line numbers at the
       start of each hex dump 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 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 hex dumps, 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 hex
       dump with xxd -r -p does not depend on the correct number  of  columns.
       Here, anything 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

       Hex  dump  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

       Hex dump from file position 0x100 (=1024-768) onwards.
       % 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

       Note:  The  results of the examples below are relevant to the xxd.1 man
       page as of May 2024

       Print 120 bytes as a continuous hex dump with 20 octets per line.
       % xxd -l 120 -ps -c 20 xxd.1
       2e544820585844203120224d6179203230323422
       20224d616e75616c207061676520666f72207878
       64220a2e5c220a2e5c222032317374204d617920
       313939360a2e5c22204d616e2070616765206175
       74686f723a0a2e5c2220202020546f6e79204e75
       67656e74203c746f6e79407363746e7567656e2e

       Hex dump the first 120 bytes of this man page with 12 octets per line.
       % xxd -l 120 -c 12 xxd.1
       00000000: 2e54 4820 5858 4420 3120 224d  .TH XXD 1 "M
       0000000c: 6179 2032 3032 3422 2022 4d61  ay 2024" "Ma
       00000018: 6e75 616c 2070 6167 6520 666f  nual page fo
       00000024: 7220 7878 6422 0a2e 5c22 0a2e  r xxd"..\"..
       00000030: 5c22 2032 3173 7420 4d61 7920  \" 21st May
       0000003c: 3139 3936 0a2e 5c22 204d 616e  1996..\" Man
       00000048: 2070 6167 6520 6175 7468 6f72   page author
       00000054: 3a0a 2e5c 2220 2020 2054 6f6e  :..\"    Ton
       00000060: 7920 4e75 6765 6e74 203c 746f  y Nugent <to
       0000006c: 6e79 4073 6374 6e75 6765 6e2e  ny@sctnugen.

       Display just the date from the file xxd.1
       % xxd -s 0x33 -l 13 -c 13 xxd.1
       00000033: 3231 7374 204d 6179 2031 3939 36  21st May 1996

       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 "0000034: 3574 68" | xxd -r - xxd.1
       % xxd -s 0x33 -l 13 -c 13 xxd.1
       00000033: 3235 7468 204d 6179 2031 3939 36  25th May 1996

       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

       Hex dump this file with autoskip.
       % xxd -a -c 12 file
       00000000: 0000 0000 0000 0000 0000 0000  ............
       *
       0000fffc: 0000 0000 41                   ....A

       Create a 1 byte file containing a single 'A' character.  The number af‐
       ter  '-r -s' adds to the line numbers 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 hex dump  a  re‐
       gion marked between `a' and `z'.
       :'a,'z!xxd

       Use xxd as a filter within an editor such as vim(1) to recover a binary
       hex dump 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 hex dump.  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 tool's weirdness matches its creator's brain.  Use entirely at your
       own risk. Copy files. Trace it. Become a wizard.

VERSION
       This manual page documents xxd version 1.7 from 2024-05.

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                May 2024                             XXD(1)