bash arrays — create, iterate, append, slice

Quick Answer

# Declare an array
fruits=("apple" "banana" "cherry")

# Access elements
echo "${fruits[0]}"        # apple
echo "${fruits[@]}"        # all elements
echo "${#fruits[@]}"       # length: 3

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

Usage

Arrays let you store lists of values and iterate over them in bash scripts.

Other causes & fixes

Append and remove elements

# Append
fruits+=("date")

# Remove element at index 1
unset 'fruits[1]'

# Re-index after removal (gaps exist otherwise)
fruits=("${fruits[@]}")

Slice and subarray

# Elements from index 1, length 2
echo "${fruits[@]:1:2}"   # banana cherry

# Last element
echo "${fruits[-1]}"

Array from command output

# Split by newline
mapfile -t files < <(find . -name "*.txt")
echo "${#files[@]} files found"

# Split by space (word splitting)
words=($( echo "one two three" ))

Associative arrays (bash 4+)

declare -A config
config["host"]="localhost"
config["port"]="5432"

echo "${config["host"]}"

for key in "${!config[@]}"; do
  echo "$key=${config[$key]}"
done