How to use 'readarray' in bash to read lines from a file into a 2D array

Question

Let\'s say I have a text file \'demo.txt\' who has a table in it like this:

1 2 3    
4 5 6    
7 8 9    

Now, I want to read each line separat

Answer 1

How can accesses each line separately and in that line get access to each member?

Per the Bash Reference Manual, Bash provides one-dimensional indexed and associative array variables. So you cannot expect matrix[1][2] or similar to work. However, you can emulate matrix access using a bash associative arrays, where the key denotes a multiple dimension.

For example, matrix[1,2] uses the string "1,2" as the associative array key denoting the 1st row, 2nd column. Combining this with readarray:

typeset -A matrix
function load() {
    declare -a a=( $2 )
    for (( c=0; c < ${#a[@]}; c++ ))
    do
        matrix[$1,$c]=${a[$c]}
    done
}
readarray -C load -c 1 <<< $'1 2 3\n4 5 6\n7 8 9'
declare -p matrix