Shell Programming and Scripting

1   2   3   4   5
10  9   8   7   6
11  12  13  14  15
..............  17

#!/bin/bash
#program for columnar transposition
#file from previous question (a)
file="encrypted.txt"

#remove all the spaces and newline and put it on a new file
name=$(cat $file)
echo $name | tr -d ' ' > temp.txt

file4="temp.txt"
name4=$(cat $file4)
echo $name4 |  sed 's/\(.\)/\1\n/g' > file4.txt

echo "enter how many cols:"
read cols

IFS=$'\n' a=($(cat file4.txt))
for j in $(seq ${#a[*]}); do
    [[ ${a[$j-1]} = $name ]] && echo "${a[$i]}"
done

for (( i=0; i<=$(( ${#a[@]} / cols )); ++i )); do
    for (( j=0; j<cols; ++j )); do
        if (( i%2 )); then idx=$(( (i + 1) / 2 * 2 * cols - j - 1 ))
        else idx=$(( (i / 2) * 2 * cols + j )); fi
        printf "%-4s  " "${a[idx]}"
    done
    printf "\n"
done