Bash 5 reference · Shell Builtins and Syntax

arrays (Bash syntax)

Indexed and associative arrays: create, append, read elements, count, slice and loop over them safely.

Bash 5

Create a free account to save this page, take notes and track your progress. Sign in

Syntax

arr=(a b c)  ${arr[i]}  ${arr[@]}  ${#arr[@]}  ${!arr[@]}  arr+=(d)

Parameter	Description
`"${arr[@]}"`	All elements, each as a separate word.
`${#arr[@]}`	Number of elements.
`${!arr[@]}`	Indexes or keys.
`${arr[@]:1:2}`	Slice: 2 elements from index 1.

Indexed arrays

servers=(web-1 web-2 'db 1')
servers+=(cache)
echo "${#servers[@]} servers, last: ${servers[-1]}"
for s in "${servers[@]}"; do echo "- $s"; done

Output

4 servers, last: cache
- web-1
- web-2
- db 1
- cache

Run this on your computer — see “Get Started” for setup.

Looping over map keys

declare -A owner=([api]=ana [web]=ben)
for k in $(printf '%s\n' "${!owner[@]}" | sort); do echo "$k: ${owner[$k]}"; done

Output

api: ana
web: ben

Run this on your computer — see “Get Started” for setup.

declare · Declare variables with attributes: arrays, associative arrays, integers, read-only values and exported variables.
mapfile · Read all lines of input into an indexed array at once (also called readarray), optionally trimming newlines with -t.
for · Loop over words, files, ranges or array elements, or use the C-style form for counters.
Bash Arrays and Associative Arrays · tutorial