Easiest way to check for an index or a key in an array?

Question

Using:

set -o nounset

1. Having an indexed array like:

   myArray=( "red" "black" "blue" )
   
   
           

Answer 1

I wrote a function to check if a key exists in an array in Bash:

# Check if array key exists
# Usage: array_key_exists $array_name $key
# Returns: 0 = key exists, 1 = key does NOT exist
function array_key_exists() {
    local _array_name="$1"
    local _key="$2"
    local _cmd='echo ${!'$_array_name'[@]}'
    local _array_keys=($(eval $_cmd))
    local _key_exists=$(echo " ${_array_keys[@]} " | grep " $_key " &>/dev/null; echo $?)
    [[ "$_key_exists" = "0" ]] && return 0 || return 1
}

Example

declare -A my_array
my_array['foo']="bar"

if [[ "$(array_key_exists 'my_array' 'foo'; echo $?)" = "0" ]]; then
    echo "OK"
else
    echo "ERROR"
fi

Tested with GNU bash, version 4.1.5(1)-release (i486-pc-linux-gnu)