> ## Documentation Index > Fetch the complete documentation index at: https://notes.kodekloud.com/llms.txt > Use this file to discover all available pages before exploring further. # Associative > This tutorial explores associative arrays in Bash, covering declaration, access, modification, and iteration in scripts. In this tutorial, you will explore **associative arrays** in Bash—powerful data structures that use named keys for direct value lookup. By the end, you’ll understand how to declare, access, modify, and iterate over associative arrays in your scripts. ## Indexed Arrays vs. Associative Arrays Think of indexed arrays as a numbered chest of drawers (0-based), and associative arrays as labeled drawers you open by name. | Array Type | Indexing Method | Declaration | | ----------------- | ----------------- | ---------------------- | | Indexed Array | Numeric, 0-based | `declare -a arr=(...)` | | Associative Array | String-based keys | `declare -A arr=(...)` | ### Example: Indexed Array (Socks Analogy) ```bash theme={null} #!/usr/bin/env bash declare -a chest_drawer=("shirts" "sports clothing" "socks" "jeans") echo "${chest_drawer[2]}" ``` ```bash theme={null} $ ./socks.sh socks ``` ## Checking Your Bash Version Associative arrays require **Bash 4.0+**. Verify with: ```bash theme={null} $ echo $BASH_VERSION 5.2.15(1)-release ``` If your Bash version is older than 4.0, associative arrays won’t work. Please upgrade before continuing. ## Declaring and Accessing an Associative Array Use `declare -A` to define an associative array. Here’s how to store and retrieve “socks” by key: ```bash theme={null} #!/usr/bin/env bash declare -A chest_drawer=( ["shirts"]="T-Shirts and polo shirts" ["sports"]="All sorts of Sports Clothing here" ["socks"]="Formal and everyday socks" ["jeans"]="Jeans, and some casual dress shorts" ) echo "${chest_drawer["socks"]}" ``` ```bash theme={null} $ ./associative-v1.sh Formal and everyday socks ``` ## Analogy: Emergency Contacts Store quick-dial numbers by department name: ```bash theme={null} #!/usr/bin/env bash declare -A emergency_contacts=( ["Fire Department"]="555-0001" ["Police Department"]="555-0002" ["Hospital"]="555-0003" ) echo "${emergency_contacts["Fire Department"]}" ``` ```bash theme={null} $ ./emergency.sh 555-0001 ``` ## Key-Value Pair Concept Associative arrays map **keys** (identifiers) to **values** (data). In Bash associative arrays, each key is unique and case-sensitive: `"Mark"` ≠ `"mark"`. ![The image explains associative arrays, highlighting the concepts of "key" as an identifier and "value" as the actual data to interact with.](https://kodekloud.com/kk-media/image/upload/v1752868543/notes-assets/images/Advanced-Bash-Scripting-Associative/associative-arrays-key-value-explained.jpg) ## Example: Email Addresses ```bash theme={null} #!/usr/bin/env bash declare -A email_addresses=( ["Mark"]="mark@email.com" ["Kriti"]="kriti@email.com" ["Feng"]="feng@email.com" ) echo "${email_addresses["Mark"]}" ``` ```bash theme={null} $ ./email-1.sh mark@email.com ``` ## Adding New Elements Assign a key in square brackets to insert or append: ```bash theme={null} #!/usr/bin/env bash declare -A email_addresses=( ["Mark"]="mark@email.com" ["Kriti"]="kriti@email.com" ["Feng"]="feng@email.com" ) # Add more contacts email_addresses["Andy"]="andy@email.com" email_addresses["Rajasekar"]="rajasekar@email.com" echo "${email_addresses[@]}" ``` ```bash theme={null} $ ./email-3.sh mark@email.com rajasekar@email.com ... ``` Associative arrays are **unordered**; iteration order can vary. ![The image is a slide about associative arrays, highlighting that they do not consider the order in which elements are stored.](https://kodekloud.com/kk-media/image/upload/v1752868544/notes-assets/images/Advanced-Bash-Scripting-Associative/associative-arrays-order-slide.jpg) ## Replacing a Value Overwrite an existing key to update its value: ```bash theme={null} #!/usr/bin/env bash declare -A email_addresses=( ["Mark"]="mark@email.com" ["Kriti"]="kriti@email.com" ["Feng"]="feng@email.com" ["Rajasekar"]="rajasekar@email.com" ) echo "Before: ${email_addresses[@]}" email_addresses["Feng"]="feng2@email.com" echo "After: ${email_addresses[@]}" ``` ```bash theme={null} $ ./email-4.sh Before: kriti@email.com ... After: kriti@email.com ... feng2@email.com ``` ## Removing Elements Use `unset` to delete by key or clear the entire array: ```bash theme={null} #!/usr/bin/env bash declare -A email_addresses=( ... ) # Remove one element unset email_addresses["Kriti"] # Remove all elements unset email_addresses ``` ## Listing Keys vs. Values * **Keys:** `${!array[@]}` * **Values:** `${array[@]}` ```bash theme={null} #!/usr/bin/env bash declare -A email_addresses=( ... ) echo "Keys: ${!email_addresses[@]}" echo "Values: ${email_addresses[@]}" ``` ## Iterating with a `for` Loop Loop through keys and access each value: ```bash theme={null} #!/usr/bin/env bash declare -A email_addresses=( ... ) for key in "${!email_addresses[@]}"; do echo "$key's email is ${email_addresses[$key]}" done ``` ```bash theme={null} $ ./email-8.sh Kriti's email is kriti@email.com ... ``` Enclose `"${!email_addresses[@]}"` in quotes to handle multi-word keys correctly. *** ## Links and References * [Bash Reference Manual](https://www.gnu.org/software/bash/manual/bash.html) * [Advanced Bash-Scripting Guide](https://tldp.org/LDP/abs/html/)