How to declare 2D array in bash

Question

I'm wondering how to declare a 2D array in bash and then initialize to 0.

In C it looks like this:

int a[4][5] = {0}; 

And how do I assign a value to an element? As in C:

a[2][3] = 3; 

Answer 1

You can simulate them for example with hashes, but need care about the leading zeroes and many other things. The next demonstration works, but it is far from optimal solution.

#!/bin/bash declare -A matrix num_rows=4 num_columns=5  for ((i=1;i<=num_rows;i++)) do     for ((j=1;j<=num_columns;j++)) do         matrix[$i,$j]=$RANDOM     done done  f1="%$((${#num_rows}+1))s" f2=" %9s"  printf "$f1" '' for ((i=1;i<=num_rows;i++)) do     printf "$f2" $i done echo  for ((j=1;j<=num_columns;j++)) do     printf "$f1" $j     for ((i=1;i<=num_rows;i++)) do         printf "$f2" ${matrix[$i,$j]}     done     echo done 

the above example creates a 4x5 matrix with random numbers and print it transposed, with the example result

           1         2         3         4  1     18006     31193     16110     23297  2     26229     19869      1140     19837  3      8192      2181     25512      2318  4      3269     25516     18701      7977  5     31775     17358      4468     30345 

The principle is: Creating one associative array where the index is an string like 3,4. The benefits:

• it's possible to use for any-dimension arrays ;) like: 30,40,2 for 3 dimensional.
• the syntax is close to "C" like arrays ${matrix[2,3]}