HexBinDecode : Some feedback on the script please

MyUsenetAccount · *nix forums beginner Joined: 06 May 2006 Posts: 3

I'd appreciate some feedback on the script below. I've limited
scripting experience but I find that it is very easy to get a script to
do the job I want but normally it is not the most efficient way.
Therefore do you have some advice on the script? What could be improved
and done cleaner/more efficient etc...?

The script works as intended. It asks the user for 5 hex bytes (no
spaces between the bytes and in upper case). It then converts this into
one long bit stream. Finally the script translates/decodes different
positions of the bit stream into some user friendly format. One problem
i have is with leading zeros being stripped from the hex->bin
conversation.

Many Thanks

#!/bin/bash
#set -x

DebugInput="8102C4C004"

echo ""
echo ""
echo "Type the data. Must be hex in upper case, 5 bytes without
spaces"

Msg_To_Translate=$DebugInput
read Msg_To_Translate #comment for automatic input. Debug Test
only

#should add functionality here to make lower case->upper case

hex=$Msg_To_Translate
binall=`echo 2o16i${hex}p|dc`
#echo binall $binall

#is it possible to perserve the leading zeros here?
#If 0x41 is the 1st byte then the bin translation is 1000001 (missing
leading zero)

#need leading zeros for 1st byte so calculate how many characters are
in the 1st byte
#and add them to the variable
#!!! Doesn't work correcly for leading characters if the 1st byte is
0x00
#the leading zeros from the 2nd byte are then missing.

byte1=${hex%????????}
byte1=`echo 2o16i${byte1}p|dc`

Length=`echo ${#byte1}`
ToAdd=$((8-$Length))
#The number in ToAdd is the number of 0's to add

#need a better method than below to add the leading spaces at the
start of the byte
#something like a shift

if [ $ToAdd -ne 0 ] #only add padding if leading zeros are missing
then

case "$ToAdd"
in
1 )
binall="0"$binall ;;
2 )
binall="00"$binall ;;
3 )
binall="000"$binall ;;
4)
binall="0000"$binall ;;
5)
binall="00000"$binall ;;
6)
binall="000000"$binall ;;
7)
binall="0000000"$binall ;;
*)
echo "Invalid 1st byte"
;;
esac

fi

#the next section performs the decoding of the various bit patterns in
the binary stram

special_bit=`echo ${binall:0:1}` #special_bit is the MSB of the 1st
byte

foo=`echo ${binall:3:5}`
foo=`echo 10o2i${foo}p|dc`

foob=`echo ${binall:11:4}`
foob=`echo 10o2i${foob}p|dc`

#.....
#.....

#print out the decoded data
echo ""
echo "special_bit is $special_bit"
echo "foo is $foo"
echo "foob is $foob"
echo ""

exit 0

Kenan Kalajdzic · *nix forums beginner Joined: 29 Apr 2006 Posts: 31

MyUsenetAccount <myusenetaccount@yahoo.co.uk> wrote:

joe@invalid.address · *nix forums Guru Wannabe Joined: 16 Jul 2005 Posts: 139

"MyUsenetAccount" <myusenetaccount@yahoo.co.uk> writes:

Google