Multi-Dimensional Array in Bash

1. Basic Way for Declaring a Multi-Dimensional Array in Bash
2. Declare 2-Dimensional Array Using an Associative Array in Bash

A multi-dimensional array is a very important element for any program. It is mainly used to create a table view of the data and for many other purposes.

This article demonstrates how to create a 2-dimensional array. Also, we will discuss the topic with necessary examples and explanations.

We will discuss two different methods here.

Basic Way for Declaring a Multi-Dimensional Array in Bash

This is the most basic method of creating a multi-dimensional array. In our example below, we will create a very basic two-dimensional array.

Below is the code for our example.

ArrayOfArray_1=("Alen" "24")
ArrayOfArray_2=("Walker" "31")
MainArray=(
  ArrayOfArray_1[@]
  ArrayOfArray_2[@]
)

ArrayLength=${#MainArray[@]}
for ((i=0; i<$ArrayLength; i++))
do
  name=${!MainArray[i]:0:1}
  age=${!MainArray[i]:1:1}
  echo "Name : ${name}"
  echo "Age : ${age}"
done

The code above shows that we declared two different arrays named ArrayOfArray_1 and ArrayOfArray_2. After that, we declared our main array, whose element is these two arrays we recently declared.

Then we calculated the length of the array for a loop. Inside the loop, we extract the data from these two sub-array by indexing the main array.

Lastly, we echo the final result. After executing the script, you will get an output like the one below.

Name : Alen
Age : 24
Name : Walker
Age : 31

Declare 2-Dimensional Array Using an Associative Array in Bash

This method is a bit complex. This method will discuss a special Bash script array named the associative array.

An associative array is a special array that can store string value as a key or index. It’s similar to the other programming languages.

The general syntax for declaring an associative array is declare -A ArrayName.

Our example below will create a 2D array containing five rows and six columns. Below is the code for our example.

declare -A Array2D
RowNum=5
ColumnNum=6

for ((i=1;i<=RowNum;i++)) do
    for ((j=1;j<=ColumnNum;j++)) do
        Array2D[$i,$j]=$RANDOM
    done
done

f1="%$((${#RowNum}+1))s"
f2=" %9s"

printf "$f1" ''
for ((i=1;i<=RowNum;i++)) do
    printf "$f2" $i
done
echo

for ((j=1;j<=ColumnNum;j++)) do
    printf "$f1" $j
    for ((i=1;i<=RowNum;i++)) do
        printf "$f2" ${Array2D[$i,$j]}
    done
    echo
done

In the example above, we declared an associative array named Array2D.

After that, we created two variables and assigned them an integer value. This integer value specifies the number of rows and columns.

Then we created a nested loop that filled the array with the random number.

Now we are done with declaring and organizing the array. It’s time to see what our 2D array looks like.

We do that by using some loops, as seen in the code. When you execute the above script, you will see an output like the below.

           1         2         3         4         5
 1     16700      5241      2599     24330      1662
 2     23264     19557     10425     13413     25606
 3     17987      4199     13598     23897     26734
 4     24420     27830     24855      8165     13531
 5     15495     18790     13347     12947     11826
 6     23458     22838       137     32454     32441

All the codes in this article are written in Bash. It will only work in the Linux Shell environment.