Let's say that I have a string 5a.
This is the hex representation of the ASCII letter Z.
I need to find a Linux shell command which will take a hex string and output the ASCII characters that the hex string represents.
So if I do:
echo 5a | command_im_looking_for
I will see a solitary letter Z:
Z
I used to do this with xxd:
echo -n 5a | xxd -r -p
But then I realised that in Debian/Ubuntu, xxd is part of vim-common and hence might not be present in a minimal system. To also avoid Perl (IMHO also not part of a minimal system), I ended up using sed, xargs, and printf like this:
echo -n 5a | sed 's/\([0-9A-F]\{2\}\)/\\\\\\x\1/gI' | xargs printf
Mostly, I only want to convert a few bytes and it's okay for such tasks. The advantage of this solution over the one of ghostdog74 is, that this can convert hex strings of arbitrary lengths automatically. xargs is used because printf doesnt read from standard input.
"echo -n 5a | xxd -r -p" I'd prefer to use "xxd -r -p <<< 5a". Advantages: (1) a few less characters to type (typing also faster because of 3x repetition); (2) runs only one command (saves the echo), not two => faster execution.
sh: 1: Syntax error: redirection unexpected disadvantage: not POSIXhere string in Bash (a concept similar to a here document).
echo -n 5a | perl -pe 's/([0-9a-f]{2})/chr hex $1/gie'
Note that this won't skip non-hex characters. If you want just the hex (no whitespace from the original string etc):
echo 5a | perl -ne 's/([0-9a-f]{2})/print chr hex $1/gie'
Also, zsh and bash support this natively in echo:
echo -e '\x5a'
perl -lne 'print pack "H*", $_'.
echo -ne '\x5a' is necessary, given the example: without the -n switch for echo, a new line ('\x0a') will be output after the Z.You can do this with echo only, without the other stuff. Don't forget to add "-n" or you will get a linebreak automatically:
echo -n -e "\x5a"
\x be inserted before each hex pair. Example was 5a, but question was about converting a hex string to multiple ASCII characters.Bash one-liner
echo -n "5a" | while read -N2 code; do printf "\x$code"; done
echo -n "0102abcd" | while read -n 2 code; do printf "\x$code"; done | hexdump yields 0201 cdab
echo -n "0102abcd" | while read -n 2 code; do printf "\x$code"; done | hexdump -e '/1 "%02x"'Some Python 3 one-liners that work with any number of bytes.
Using strip, so that it's ok to have a newline on stdin.
$ echo 666f6f0a | python3 -c "import sys, binascii; sys.stdout.buffer.write(binascii.unhexlify(input().strip()))"
foo
$ echo foo | python3 -c "import sys, binascii; print(binascii.hexlify(sys.stdin.buffer.read()).decode())"
666f6f0a
python3 -c 'import binascii; print(binascii.unhexlify(input()))' <<< 486921dc can convert between numeric bases:
$ echo 5a | (echo 16i; tr 'a-z' 'A-Z'; echo P) | dc
Z$
Depending on where you got that "5a", you can just prepend "\x" to it and pass that to printf:
$ a=5a
$ a="\x${a}"
$ printf "$a"
Z
printf "\x${a}"echo 5a | python -c "import sys; print chr(int(sys.stdin.read(),base=16))"
print to sys.stdout.write to prevent the extra linefeed character.
OverflowError: Python int too large to convert to C longHere is a pure bash script (as printf is a bash builtin) :
#warning : spaces do matter
die(){ echo "$@" >&2;exit 1;}
p=48656c6c6f0a
test $((${#p} & 1)) == 0 || die "length is odd"
p2=''; for ((i=0; i<${#p}; i+=2));do p2=$p2\\x${p:$i:2};done
printf "$p2"
If bash is already running, this should be faster than any other solution which is launching a new process.
for ((i=0; i<${#p}; i+=2));do p2+=\\x${p:$i:2};doneThere is a simple shell command ascii.
If you use Ubuntu, install it with:
sudo apt install ascii
Then
ascii 0x5a
will output:
ASCII 5/10 is decimal 090, hex 5a, octal 132, bits 01011010: prints as `Z'
Official name: Majuscule Z
Other names: Capital Z, Uppercase Z
As per @Randal comment, you can use perl, e.g.
$ printf 5a5a5a5a | perl -lne 'print pack "H*", $_'
ZZZZ
and other way round:
$ printf ZZZZ | perl -lne 'print unpack "H*", $_'
5a5a5a5a
Another example with file:
$ printf 5a5a5a5a | perl -lne 'print pack "H*", $_' > file.bin
$ perl -lne 'print unpack "H*", $_' < file.bin
5a5a5a5a
You can use this command (python script) for larger inputs:
echo 58595a | python -c "import sys; import binascii; print(binascii.unhexlify(sys.stdin.read().strip()).decode())"
The result will be:
XYZ
And for more simplicity, define an alias:
alias hexdecoder='python -c "import sys; import binascii; print(binascii.unhexlify(sys.stdin.read().strip()).decode())"'
echo 58595a | hexdecoder
GNU awk 4.1
awk -niord '$0=chr("0x"RT)' RS=.. ORS=
Note that if you echo to this it will produce an extra null byte
$ echo 595a | awk -niord '$0=chr("0x"RT)' RS=.. ORS= | od -tx1c
0000000 59 5a 00
Y Z \0
Instead use printf
$ printf 595a | awk -niord '$0=chr("0x"RT)' RS=.. ORS= | od -tx1c
0000000 59 5a
Y Z
Also note that GNU awk produces UTF-8 by default
$ printf a1 | awk -niord '$0=chr("0x"RT)' RS=.. ORS= | od -tx1
0000000 c2 a1
If you are dealing with characters outside of ASCII, and you are going to be
Base64 encoding the resultant string, you can disable UTF-8 with -b
echo 5a | sha256sum | awk -bniord 'RT~/\w/,$0=chr("0x"RT)' RS=.. ORS=
Similar to my answer here: Linux shell scripting: hex number to binary string
You can do it with the same tool like this (using ascii printable character instead of 5a):
echo -n 616263 | cryptocli dd -decoders hex
Will produce the following result:
abcd
