Arrays

Code

#!/bin/bash

# Declare array
fruits=("apple" "banana" "cherry")
nums=(1 2 3 4 5)

# Associative array (requires bash 4+)
declare -A ages
ages["Alice"]=30
ages["Bob"]=25

# Access element
echo ${fruits[0]}      # apple
echo ${fruits[-1]}     # cherry (last element)
echo ${ages["Alice"]}  # 30

# All elements
echo ${fruits[@]}      # apple banana cherry
echo ${fruits[*]}      # apple banana cherry
echo ${!fruits[@]}     # 0 1 2 (indices)
echo ${!ages[@]}       # Alice Bob (keys)

# Array length
echo ${#fruits[@]}     # 3
echo ${#fruits[0]}     # 5 (first element length)

# Add element
fruits+=("date" "elderberry")

# Modify element
fruits[0]="apricot"

# Delete element
unset fruits[1]        # Delete index 1
unset fruits           # Delete entire array

# Slice
echo ${fruits[@]:1:2}  # Take 2 from index 1

# Iterate
for fruit in "${fruits[@]}"; do
    echo "Fruit: $fruit"
done

# Iterate associative array
for key in "${!ages[@]}"; do
    echo "$key is ${ages[$key]}"
done

# Create array from string
str="a,b,c,d"
IFS=',' read -ra arr <<< "$str"
echo ${arr[2]}  # c

# Sort
sorted=($(printf '%s\n' "${fruits[@]}" | sort))
echo ${sorted[@]}

Explanation

Bash supports indexed and associative arrays; ${arr[@]} gets all elements; ${#arr[@]} gets the length.

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