Get Nth character with Sed

Question

I'm in the middle of Playing Final Fantasy 7, and I'm at the part where you're in the Library at Shinra HQ and you have to write down the Nth letter--minus the spaces, where Nth is the number in front of the book's title--for every book that doesn't seem to belong in the current room, of which there are 4.

I need a sed script or other command-line to print the title of the book and get the Nth letter in its name.

Answer 1

You don't need sed for that. You can use bash string substitution:

$ book="The Ancients in History"
$ book="${book// /}"   # Do global substition to remove spaces
$ echo "${book:13:1}"  # Start at position 13 indexed at 0 and print 1 character
H

Answer 2

I figured out how to do it:

echo "The Ancients in History" | sed -r 's/\s//g ; s/^(.{13})(.).*$/\2/'

=> H

NOTE
Sed starts counting at 0 instead of 1, so if you want the 14th letter, ask for the 13th one.

Here's it in a shell script:

#!/bin/sh

if [[ -n "$1" ]]; then # string 

    if [[ -n "$2" ]]; then # Nth 

        echo "Getting character" $[$2 - 1]

        export Nth=$[$2 - 1]

        echo "$1" | sed -r "s/\s//g ; s/^(.{$Nth})(.).*$/\2/";
    fi
fi