Check if an element is present in a Bash array [duplicate]

by

You could do:

if [[ " ${arr[*]} " == *" d "* ]]; then
    echo "arr contains d"
fi

This will give false positives for example if you look for “a b” — that substring is in the joined string but not as an array element. This dilemma will occur for whatever delimiter you choose.

The safest way is to loop over the array until you find the element:

array_contains () {
    local seeking=$1; shift
    local in=1
    for element; do
        if [[ $element == "$seeking" ]]; then
            in=0
            break
        fi
    done
    return $in
}

arr=(a b c "d e" f g)
array_contains "a b" "${arr[@]}" && echo yes || echo no    # no
array_contains "d e" "${arr[@]}" && echo yes || echo no    # yes

Here’s a “cleaner” version where you just pass the array name, not all its elements

array_contains2 () { 
    local array="$1[@]"
    local seeking=$2
    local in=1
    for element in "${!array}"; do
        if [[ $element == "$seeking" ]]; then
            in=0
            break
        fi
    done
    return $in
}

array_contains2 arr "a b"  && echo yes || echo no    # no
array_contains2 arr "d e"  && echo yes || echo no    # yes

For associative arrays, there’s a very tidy way to test if the array contains a given key: The -v operator

$ declare -A arr=( [foo]=bar [baz]=qux )
$ [[ -v arr[foo] ]] && echo yes || echo no
yes
$ [[ -v arr[bar] ]] && echo yes || echo no
no

See 6.4 Bash Conditional Expressions in the manual.

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