xxd - make a hexdump or do the reverse.

       xxd -h[elp]
       xxd [options] [infile [outfile]]
       xxd -r[evert] [options] [infile [outfile]]
creates a hex dump of a given file or standard input or
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 standard output.
It can be used to perform binary file patching.

If infile is specified as a - or if no infile is given, stdin is read.
If no outfile is given (or a - character is in its place), output is to stdout

Only the first option letter is used, 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 equivalent.

toggle autoskip: A single '*' replaces nul-lines. Default off.
-c cols
-cols cols
format <cols> octets per line. Default 16 (-i: 12, -ps: 30, -b: 6). Max 256.
-g b
-groupsize b
separate the output of every <b> bytes (two hex characters or eight bit-digits each) by a whitespace.
Specify -g 0 to suppress grouping.
Default: 2 in normal mode and 1 in bits mode.
Grouping does not apply to postscript or include style.
output in C include file style. A complete static array definition is written (named after the input file), unless xxd reads from stdin.
reverse operation: convert (or patch) hexdump into binary. 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 anywhere.
-l len
-len len
stop after writing <len> octets.
-seek offset 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.
binary digits dump
Each line is preceded by a line number in hexadecimal and followed by an ASCII (or EBCDIC) representation.
-r, -p, -i are not used.
output in postscript continuous hexdump style. Also known as plain hexdump style.
The character encoding in the righthand column is EBCDIC.
This does not change the hexadecimal representation. The option is meaningless in combinations with -r, -p or -i.


xxd -r has some builtin magic while evaluating line number information. If the output 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 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, xxd -r skips everything on the input line after reading enough columns of hexadecimal data (see option -c). changes to the printable text columns are always ignored.
Reverting a plain (or postscript) style hexdump with xxd -r -p does not depend on the correct number of columns. Anything that looks like a pair of hex-digits is interpreted.

Note the difference between

       % xxd -i file
       % 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. Examples: 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 this is a rare situation and the use of `+' is rarely needed. monitor the effect of xxd with strace(1) or truss(1), whenever -s is used.


       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 20 octets per line.
       % xxd -l 120 -ps -c 20 xxd.1

       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 2241  .TH XXD 1 "A
       000000c: 7567 7573 7420 3139 3936 2220  ugust 1996"
       0000018: 224d 616e 7561 6c20 7061 6765  "Manual page
       0000024: 2066 6f72 2078 7864 220a 2e5c   for xxd"..\
       0000030: 220a 2e5c 2220 3231 7374 204d  "..\" 21st M
       000003c: 6179 2031 3939 360a 2e5c 2220  ay 1996..\"
       0000048: 4d61 6e20 7061 6765 2061 7574  Man page aut
       0000054: 686f 723a 0a2e 5c22 2020 2020  hor:..\"
       0000060: 546f 6e79 204e 7567 656e 7420  Tony Nugent
       000006c: 3c74 6f6e 7940 7363 746e 7567  <tony@sctnug

       Display just the date from the file xxd.1
       % xxd -s 0x36 -l 13 -c 13 xxd.1
       0000036: 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 "0000037: 3574 68" | xxd -r - xxd.1    # 3574 68  (c=  5th
       % xxd -s 0x36 -l 13 -c 13 xxd.1
       0000036: 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

       Hexdump that 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'.

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

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

Create a C include:

    xxd -i samp 0000.c

    cat 0000.c
unsigned char samp[] = {
  0x20, 0x41, 0x46, 0x4b, 0x50, 0x55, 0x5a, 0x0a, 0x20, 0x42, 0x47, 0x4c,
  0x51, 0x56, 0x0a, 0x20, 0x43, 0x48, 0x4d, 0x52, 0x57, 0x0a, 0x20, 0x44,
  0x49, 0x4e, 0x53, 0x58, 0x0a, 0x20, 0x45, 0x4a, 0x4f, 0x54, 0x59, 0x3a,
  0x58, 0x0a, 0x0a
unsigned int samp_len = 39;

       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 


       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.


uuencode(1), uudecode(1), patch(1)