[bash] ASCII to HEX and hex to ascii

////// · 09-30-2006, 09:01 PM

What kind of command should I use to translate ascii to hex in a bash script ? (and hex back to ascii)

TIA

/////

paulsm4 · 09-30-2006, 09:30 PM

do you mean something like this?

Code:

echo 0x41 | awk '{printf "%c\n", $1}'
A

The other direction (like an "ord(char)" function), is much less straightforward. Here are a couple of interesting solutions:

http://devworld.apple.com/documentat...section_3.html

And here's yet another possibility:

Code:

echo A|hexdump
0000000 0a41
0000002

... or, equivalently ...

Code:

echo A|od -x
0000000 0a41
0000002

////// · 09-30-2006, 09:53 PM

Hi, yes something like that. Only but is that..

Code:

echo 0x41 | awk '{printf "%c\n", $1}'
0

..this doesn't work in my box

awk -W version
GNU Awk 3.1.5

Code:

awk '{printf "%c\n", $1}' /root/Desktop/testfile # testfile contains 0x41
0

it woold be good if it worked with words, not just single letters.

Cheers

////

Edit: Thank you, I can use that hexdump, and that link is a nice one

spirit receiver · 10-01-2006, 08:48 AM

Quote:

Originally Posted by //////

..this doesn't work in my box

Try the following instead (with Bash):

Code:

ada@barnabas:~> echo -e "\x41" | awk '{printf "%c\n", $1}'
A

Edit: Sorry, I guess this is nonsense.

ghostdog74 · 10-01-2006, 09:50 AM

alternative in Python:

ascii to hex:

Code:

#!/usr/bin/python
hex(ord('a'))

output:
'0x61'

hex to ascii

Code:

import binascii
binascii.a2b_hex("61")

output:
'a'

spirit receiver · 10-01-2006, 10:12 AM

... and I just learned that there's a package named uni2ascii which does the following:

Code:

ada@barnabas:~> echo "ABCDE" | uni2ascii -Bsepq
\x0041\x0042\x0043\x0044\x0045
ada@barnabas:~> echo "ABCDE" | uni2ascii -Bsepq | ascii2uni -Bq
ABCDE

////// · 10-01-2006, 10:55 AM

Quote:

Originally Posted by spirit receiver

... and I just learned that there's a package named uni2ascii which does the following:

Code:

ada@barnabas:~> echo "ABCDE" | uni2ascii -Bsepq
\x0041\x0042\x0043\x0044\x0045
ada@barnabas:~> echo "ABCDE" | uni2ascii -Bsepq | ascii2uni -Bq
ABCDE

Thanks guys, that uni2ascii is a good one, just compiled it and it does its job nicely.

osor · 10-01-2006, 12:18 PM

There's a nice utility that comes with Vim called xxd. It is script-friendly, and (unlike od or hexdump) has the ability to go back and forth (with the revert option).

For example, you could have something like:

Code:

... | xxd -g 1 -c 1 | awk ...

Where there are three fields you can access in awk. $1 is the offset (in hex), $2 is the two-digit hex representation of a byte, and $3 is the ASCII representation of the byte (or just a period for nonprintable characters).

For going back, just do something like:

Code:

... | xxd -p -s -

The only formatting restrictions on the input is that single bytes appear together as two-digit numbers. It doesn't care about formatting or whitespace (the -p is for plain).

I guess xxd's not as portable as hexdump or od, but it is probably more portable than uni2ascii (i.e., is more likely to be found installed on a *nix machine than uni2ascii).

////// · 10-01-2006, 12:44 PM

Quote:

Originally Posted by osor

I guess xxd's not as portable as hexdump or od, but it is probably more portable than uni2ascii (i.e., is more likely to be found installed on a *nix machine than uni2ascii).

Thats true, but I'm not that concerned about portability, (I'm using slax based Back|Track and adding modules is easy) and I'm not doing anything really important, just learning to write my own snort rules and I was getting tired to visit online hex translators

But anyways, that ascii2hex is working nicely with my script so thanks again.

Code:

slax ~ # /root/Desktop/trans 'Hello there !'
48 65 6C 6C 6F 20 74 68 65 72 65 20 21