Bash 5 reference · Shell Builtins and Syntax

declare (Bash builtin)

Declare variables with attributes: arrays, associative arrays, integers, read-only values and exported variables.

Bash 5

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Syntax

declare [-a|-A|-i|-r|-x|-l|-u|-p] NAME[=VALUE]...

Parameter	Description
`-A`	Associative array (map).
`-i`	Integer: assignments are evaluated arithmetically.
`-r`	Read-only.
`-x`	Export to child processes.
`-l / -u`	Lowercase / uppercase on assignment.
`-p`	Print declarations.

An associative array

declare -A port=([web]=80 [api]=8080)
echo "api on ${port[api]}, ${#port[@]} services"

Output

api on 8080, 2 services

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

Case, integer and read-only attributes

declare -u code=abc; declare -i n=2+3
echo "$code $n"
declare -r FIXED=1
(FIXED=2) 2>/dev/null || echo 'FIXED is read-only'

Output

ABC 5
FIXED is read-only

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

arrays · Indexed and associative arrays: create, append, read elements, count, slice and loop over them safely.
local · Declare variables that exist only inside the current function, so they don't overwrite globals with the same name.
export · Mark variables so child processes inherit them; one-off variables can also be set for a single command.
Bash Arrays and Associative Arrays · tutorial