xxd能将一个给定文件或标准输入转换为十六进制形式，也能将十六进制转换回二进制形式。

Usage:
       xxd [options] [infile [outfile]]
    or
       xxd -r [-s [-]offset] [-c cols] [-ps] [infile [outfile]]
Options:
    -a          toggle autoskip: A single '*' replaces nul-lines. Default off.
    -b          binary digit dump (incompatible with -ps,-i,-r). Default hex.
    -c cols     format <cols> octets per line. Default 16 (-i: 12, -ps: 30).
    -E          show characters in EBCDIC. Default ASCII.
    -g          number of octets per group in normal output. Default 2.
    -h          print this summary.
    -i          output in C include file style.
    -l len      stop after <len> octets.
    -ps         output in postscript plain hexdump style.
    -r          reverse operation: convert (or patch) hexdump into binary.
    -r -s off   revert with <off> added to file positions found in hexdump.
    -s [+][-]seek  start at <seek> bytes abs. (or +: rel.) infile offset.
    -u          use upper case hex letters.
    -v          show version: "xxd V1.10 27oct98 by Juergen Weigert".

实例：以每组两个字节十六进制输出
# xxd test

实例：以每组一个字节按大写字母十六进制输出
# xxd -g 1 -u  test

实例：以每组一个字节按C风格数组十六进制输出
# xxd -g 1 -i  test