Check if a variable exists in a list in Bash

Question

I am trying to write a script in bash that check the validity of a user input.
I want to match the input (say variable x) to a list of valid values.

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Answer 1

If your list of values is to be hard-coded in the script, it's fairly simple to test using case. Here's a short example, which you can adapt to your requirements:

for item in $list
do
    case "$x" in
      item1|item2)
        echo "In the list"
        ;;
      not_an_item)
        echo "Error" >&2
        exit 1
        ;;
    esac
done

If the list is an array variable at runtime, one of the other answers is probably a better fit.