Assigning the value of an array to a variable bash script

Question

I want to ask about the syntax i use to assign a value of a two dimensional array element to a variable. this is basically what i am trying to do: I have a 2 dimensional array of characters and a string called sub_string that gets the value of a particular element in the array and put it in another string called whole_string

for ((j=1;j<=num_columns;j++)) do
      for ((i=1;i<=num_rows;i++)) do

Assigning the value of the element [i,j] in the array matrix to a sub string

    whole_string="$whole_String$sub_string"
    done
done

I want to know how to assign the value of the array to the sub string i have. thank you

bash does not have two-dimensional arrays, nor can you store an array inside another array. — chepner
– chepner, Commented Aug 31, 2014 at 18:58
...well, one can escape an array -- as in printf -v arr_str '%q ' "${arr[@]}" -- and store the resulting string as an array element... but still the question is far, far too vague and unclear to understand whether this would actually be in furtherance of a reasonable goal. — Charles Duffy
– Charles Duffy, Commented Aug 31, 2014 at 19:01
A one-dimensional associative array with keys of the form ${x}_$y is sometimes good enough to simulate a two-dimensional array... but again, question much too unclear. — Charles Duffy
– Charles Duffy, Commented Aug 31, 2014 at 19:01
Sure, there are lots of way to fake it, but it's debatable whether any are worth the effort. If you need such a data structure, bash (or any shell I can think of) is the wrong choice. — chepner
– chepner, Commented Aug 31, 2014 at 19:03

Cyrus · Accepted Answer · 2014-08-31 19:38:24Z

3

With a current bash you can divert an associative array to create multidimensional arrays.

#!/bin/bash

declare -A A    # declare associative array A
num_rows=7
num_columns=9

# fill array
for ((j=1;j<=num_rows;j++)) do
  for ((i=1;i<=num_columns;i++)) do
    A[$j,$i]="$j:$i"   # fill with row:column
  done
done

# print array
for ((j=1;j<=num_rows;j++)) do
  for ((i=1;i<=num_columns;i++)) do
    echo -n "${A[$j,$i]} "
  done
  echo
done

Output (9x7 array):

1:1 1:2 1:3 1:4 1:5 1:6 1:7 1:8 1:9 
2:1 2:2 2:3 2:4 2:5 2:6 2:7 2:8 2:9 
3:1 3:2 3:3 3:4 3:5 3:6 3:7 3:8 3:9 
4:1 4:2 4:3 4:4 4:5 4:6 4:7 4:8 4:9 
5:1 5:2 5:3 5:4 5:5 5:6 5:7 5:8 5:9 
6:1 6:2 6:3 6:4 6:5 6:6 6:7 6:8 6:9 
7:1 7:2 7:3 7:4 7:5 7:6 7:7 7:8 7:9

answered Aug 31, 2014 at 19:38

Cyrus

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