Convert xxd output to shellcode Taking some output from xxd and turning it into usable shellcode by hand is no fun, so your job is to automate the process.

Rules

Your submission can be a function, lambda, script, or any reasonable equivalent of those. You may print the result, or if your submission is a function/lambda then you may also return it.

You program must take three arguments, the first being a string containing the output of xxd, ran with no arguments other than a filename, like this: xxd some_file. Here's an example of what the the first argument will look like:

00000000: 31c0 b046 31db 31c9 cd80 eb16 5b31 c088  1..F1.1.....[1..
00000010: 4307 895b 0889 430c b00b 8d4b 088d 530c  C..[..C....K..S.
00000020: cd80 e8e5 ffff ff2f 6269 6e2f 7368 4e58  ......./bin/shNX
00000030: 5858 5859 5959 59                        XXXYYYY


Your need to take that middle section containing the bytes (the first 8 columns after the :) and turn it into shellcode by removing any whitespace, then putting a \x before each byte.

Here's what the output should be for the input above (ignoring any other arguments):

\x31\xc0\xb0\x46\x31\xdb\x31\xc9\xcd\x80\xeb\x16\x5b\x31\xc0\x88\x43\x07\x89\x5b\x08\x89\x43\x0c\xb0\x0b\x8d\x4b\x08\x8d\x53\x0c\xcd\x80\xe8\xe5\xff\xff\xff\x2f\x62\x69\x6e\x2f\x73\x68\x4e\x58\x58\x58\x58\x59\x59\x59\x59

You can assume the first argument will always be a valid xxd output, ran with no arguments other than the filename. 

Your output should also be a string where the backslashes are literal backslashes, not used as escape characters. So when I say "\x65", I'm not talking about the byte 0x65, or even the letter "A". In code, it would be the string "\x65".

The second argument specifies where in the xxd output the shellcode should start, and the third specifies where it should end. If the third argument is -1, it will end at the end of xxd output. The second and third argument will also always be non negative, except for when the third is -1

Here are some test cases:

Argument 1:

00000000: 31c0 b046 31db 31c9 cd80 eb16 5b31 c088  1..F1.1.....[1..
00000010: 4307 895b 0889 430c b00b 8d4b 088d 530c  C..[..C....K..S.
00000020: cd80 e8e5 ffff ff2f 6269 6e2f 7368 4e58  ......./bin/shNX
00000030: 5858 5859 5959 59                        XXXYYYY


Argument 2: 7, Argument 3: e (these are both strings representing hexadecimal numbers)

Output: \xc9\xcd\x80\xeb\x16\x5b\x31\xc0

Argument 1:

00000000: 31c0 b046 31db 31c9 cd80 eb16 5b31 c088  1..F1.1.....[1..
00000010: 4307 895b 0889 430c b00b 8d4b 088d 530c  C..[..C....K..S.
00000020: cd80 e8e5 ffff ff2f 6269 6e2f 7368 4e58  ......./bin/shNX
00000030: 5858 5859 5959 59                        XXXYYYY


Argument 2: 0, Argument 3: 2e

Output: \x31\xc0\xb0\x46\x31\xdb\x31\xc9\xcd\x80\xeb\x16\x5b\x31\xc0\x88\x43\x07\x89\x5b\x08\x89\x43\x0c\xb0\x0b\x8d\x4b\x08\x8d\x53\x0c\xcd\x80\xe8\xe5\xff\xff\xff\x2f\x62\x69\x6e\x2f\x73\x68\x4e

Argument 1:

00000000: 31c0 b046 31db 31c9 cd80 eb16 5b31 c088  1..F1.1.....[1..
00000010: 4307 895b 0889 430c b00b 8d4b 088d 530c  C..[..C....K..S.
00000020: cd80 e8e5 ffff ff2f 6269 6e2f 7368 4e58  ......./bin/shNX
00000030: 5858 5859 5959 59                        XXXYYYY


Argument 2: a, Argument 3: -1

Output: \xeb\x16\x5b\x31\xc0\x88\x43\x07\x89\x5b\x08\x89\x43\x0c\xb0\x0b\x8d\x4b\x08\x8d\x53\x0c\xcd\x80\xe8\xe5\xff\xff\xff\x2f\x62\x69\x6e\x2f\x73\x68\x4e\x58\x58\x58\x58\x59\x59\x59\x59

The code with the least bytes wins. The winner will be announced in seven days, on August 15, 2016 (but submissions after then are still appreciated).

Update

Congrats to @Adnan to winning the challenge!
Bash + coreutils + xxd, 73 71 69 bytes



printf \\x%s `xxd -r|xxd -p -s0x$1 -l$[(e=1+0x$2)?e-0x$1:-1]|fold -2`


Expects the hexdump on STDIN and start/end as command-line arguments.

This prints some warnings to STDERR, which is allowed by default.