BASH Programming

How to Define Hash Table in Bash Programming

A hash table, also known as an associative array, is a data structure in the Bash shell that allows you to store and retrieve values based on keys. Hash tables are useful for implementing data structures such as dictionaries, caches, and sets. To read more on how to define and use the hash table in Linux go through this guide.

What is a Hash Table

A hash table is a data structure that stores data as key-value pairs and gives an efficient way to store, retrieve, and update data in a well-structured manner. The key in the hash table is used as an index to access the corresponding value, making the hash table an ideal choice for storing and accessing data when the data size is large.

How to Define Hash Table in Bash Programming

In Bash, a hash table is defined using an associative array, there are few steps that one should follow and the first one to create an associative array using the following syntax:

declare -A <your-array>


Next, you need to enter the values in the hash table by using the array declared previously, so follow the given syntax:



Now you can also add more than one keys in this array at the same time or otherwise you can do it separately using the above given syntax and afterwards retrieve the data through value, for that use the below given syntax:



To illustrate in a more detailed way I have composed an example of creating a hash table that uses the same syntax described above, here is its code:

# Declare an associative array

declare -A company_details

# Store employee information in the hash table
company_details=([name]="Linuxhint" [Region]=USA [Category]="Linux" [department>

# Access employee information stored in the hash table
echo "Name: ${company_details[name]}"
echo "Region: ${company_details[Region]}"
echo "Category: ${company_details[Category]}"
echo "Department: ${company_details[department]}"


Now simply create a bash file and place the code given above:

Afterwards just execute the code using bash command, here is the output of the example code that is given above:

$ bash


Here is the brief explanation of the example code that I have used for demonstration purposes:

1: The declare keyword is used to declare variables in Bash, and the -A option is used to specify that the variable is an associative array.

2: The values “Linuxhint”, “USA”, “Linux”, and an empty string are stored in the associative array under the keys “name”, “Region”, “Category”, and “department”, respectively.

3: The ${company_details[key]}, where “key” is the index or key of the associative array. We use the echo command to print the values to the console.


Hash tables, also known as associative arrays in the context of Bash programming, provide a flexible and efficient way to store, retrieve, and update data in a script. By using associative arrays, you can simplify your scripts and make them more efficient, especially when you need to store and access related data. This guide explained what a hash table is and how to define it in bash with the help of a practical example along with the syntax.

About the author

Aaliyan Javaid

I am an electrical engineer and a technical blogger. My keen interest in embedded systems has led me to write and share my knowledge about them.