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