Checking if length of array is equal to a variable in bash

Question

I want to check if the length of a bash array is equal to a bash variable (int) or not. My current code looks like this:

if [ "${#selected_columns}" -eq "${number_of_columns}" ]; then
    echo "They are equal!"
fi

This returns false since the echo statement is never run. However, doing this produces 4 for both of them:

echo "${#selected_columns[@]}"
echo "${number_of_columns}"

What's wrong here? Has it something to do with string versus int?

Answer 1

In your:

if [ "${#selected_columns}" -eq "${number_of_columns}" ]; then
    echo "They are equal!"
fi

${#selected_columns} is missing [@].

Fixed:

if [ "${#selected_columns[@]}" -eq "${number_of_columns}" ]; then
    echo "They are equal!"
fi