Check if a Bash array contains a value

Question

In Bash, what is the simplest way to test if an array contains a certain value?

Answer 1

One-line check without 'grep' and loops

if ( dlm=$'\x1F' ; IFS="$dlm" ; [[ "$dlm${array[*]}$dlm" == *"$dlm${item}$dlm"* ]] ) ; then
  echo "array contains '$item'"
else
  echo "array does not contain '$item'"
fi

This approach uses neither external utilities like grep nor loops.

What happens here, is:

• we use a wildcard substring matcher to find our item in the array that is concatenated into a string;
• we cut off possible false positives by enclosing our search item between a pair of delimiters;
• we use a non-printable character as delimiter, to be on the safe side;
• we achieve our delimiter being used for array concatenation too by temporary replacement of the IFS variable value;
• we make this IFS value replacement temporary by evaluating our conditional expression in a sub-shell (inside a pair of parentheses)