hey this is my first post here and i am desperately looking for some help! Im trying to write a shell script for the first time and ive run into some issues.

Im writing a script that takes two strings as parameters, im then using sed to do replacements of the first string over the second string for given files.

eg sed "sl/$1/$2/g" "$file"

so this works fine and replaces the whole string with the whole string, now i need to work char by char. So given inputs of $1=abcd $2=ABCD, i need sed to replace all instances of a with A, b with B, c with C etc. Ive tried a few things already, and the way i was attempting was calling sed -e for each char, this is obviously a horrid way of doing it :P

Im not a programming noob by any stretch of the word but this is giving me real issues Any help would be appreciated, thanks.

Using sed at all would be horrid. Switch to tr for this:

I agree that tr is definitely the tool of choice here, but it wouldn't be too tricky with sed either:

OMG I KNEW there was a painfully simple way of doing what i wanted!! You have no idea the pain that has caused me, about 3 solid hours trying all sorts of kludges to get it to go. that'll teach me not to read th man pages thoroughly enough! Thankyou so much, i feel like such a retard :P