1、xxd命令主要用來查看文件對應的十六進制形式，也可以講文件對應的十六進制形式輸出到一個指定的文件。
使用此命令所支持的特有選項，亦可以以二進制的形式查看文件。
關於此命令經常使用的選項主要有：
（1）-a : 它的作用是自動跳過空白內容，默認是關閉的
（2）-c : 它的後面加上數字表示每行顯示多少字節的十六進制數，默認是16bytes，最大是256bytes
（3）-g : 設定以幾個字節爲一塊，默認爲2bytes
（4）-l : 顯示多少字節的內容
（5）-s : 後面接【+-】和address。“+”表示從地址處開始的內容，“-”表示距末尾address開始的內容
（6）-b:以二進制（0 or 1）的形式查看文件內容
（7）-r: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 hexadecimal dumps without line number information and without a particular column layout. Additional Whitespace and line-breaks are allowed anywhere.（翻譯功力差，直接上原文）
我們可以使用 man 命令查看xxd命令的詳細解釋：man xxd ，部分信息如下：
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 鈥榤ail-safe鈥?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 `-鈥?character, then
input is taken from standard input. If no outfile is given (or a `-鈥?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 鈥?鈥?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 hexadecimal dump. Each line is preceded
by a line number in hexadecimal and followed by an ascii (or ebcdic) representation. The
command line switches -r, -p, -i do not work with this mode.
-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
separate the output of every <bytes> bytes (two hex characters or eight bit-digits each)
by a whitespace. 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 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.
-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 rela-
tive 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.
2、xxd命令的簡單應用
2.1 顯示文件的十六進制形式
-bash-3.2$ xxd demon.c
0000000: 2369 6e63 6c75 6465 203c 7374 6469 6f2e #include <stdio.
0000010: 683e 0a2f 2f74 6869 7320 6973 206d 6169 h>.//this is mai
0000020: 6e20 6675 6e63 0a69 6e74 206d 6169 6e28 n func.int main(
0000030: 290a 7b0a 2020 2020 696e 7420 6e75 6d20 ).{. int num
0000040: 3d31 303b 0a20 2020 2070 7269 6e74 6628 =10;. printf(
0000050: 226e 756d 6265 7220 6973 2025 645c 6e22 "number is %d\n"
0000060: 2c6e 756d 293b 0a20 2020 2072 6574 7572 ,num);. retur
0000070: 6e20 303b 0a7d 0a0a n 0;.}..
2.2 將十六進制顯示的內容輸出到制定文件
xxd demon.c demon.xxd
xxd命令 原文件 輸出到的目標文件
2.3 以二進制形式顯示文件內容 （-b選項的使用）
-bash-3.2$ xxd -b demon.c
0000000: 00100011 01101001 01101110 01100011 01101100 01110101 #inclu
0000006: 01100100 01100101 00100000 00111100 01110011 01110100 de <st
000000c: 01100100 01101001 01101111 00101110 01101000 00111110 dio.h>
0000012: 00001010 00101111 00101111 01110100 01101000 01101001 .//thi
0000018: 01110011 00100000 01101001 01110011 00100000 01101101 s is m
000001e: 01100001 01101001 01101110 00100000 01100110 01110101 ain fu
0000024: 01101110 01100011 00001010 01101001 01101110 01110100 nc.int
000002a: 00100000 01101101 01100001 01101001 01101110 00101000 main(
0000030: 00101001 00001010 01111011 00001010 00100000 00100000 ).{.
0000036: 00100000 00100000 01101001 01101110 01110100 00100000 int
000003c: 01101110 01110101 01101101 00100000 00111101 00110001 num =1
0000042: 00110000 00111011 00001010 00100000 00100000 00100000 0;.
0000048: 00100000 01110000 01110010 01101001 01101110 01110100 print
000004e: 01100110 00101000 00100010 01101110 01110101 01101101 f("num
0000054: 01100010 01100101 01110010 00100000 01101001 01110011 ber is
000005a: 00100000 00100101 01100100 01011100 01101110 00100010 %d\n"
0000060: 00101100 01101110 01110101 01101101 00101001 00111011 ,num);
0000066: 00001010 00100000 00100000 00100000 00100000 01110010 . r
000006c: 01100101 01110100 01110101 01110010 01101110 00100000 eturn
0000072: 00110000 00111011 00001010 01111101 00001010 00001010 0;.}..
2.4 指定顯示文件的字節數
-bash-3.2$ xxd -l 16 demon.c
0000000: 2369 6e63 6c75 6465 203c 7374 6469 6f2e #include <stdio.
使用 -l參數，限定只顯示16 bytes的內容