How to select a random item from an array in shell

Question

I'm creating a bot in Shell Script:

# Array with expressions
expressions=("Ploink Poink" "I Need Oil" "Some Bytes are Missing!" "Poink Poink" "Piiiip Beeeep!!" "Hello" "Whoops! I'm out of memmory!")

# Seed random generator
RANDOM=$$$(date +%s)

# Loop loop loop loop loop loop ...
while [ 1 ]
do
    # Get random expression...
    selectedexpression=${expressions[$RANDOM % ${#RANDOM[*]}]}

    # Write to Shell
    echo $selectedexpression


    # Wait an half hour
    sleep 1 # It's one second for debugging, dear SOers
done

I want that it prints a random item from the expressions every second. I tried this but it does not work. It only prints the first one (Ploink Poink) every time. Can anyone help me out? Thanks

Answer 1

Change the line where you define selectedexpression to

selectedexpression=${expressions[$RANDOM % ${#expressions[@]} ]}

You want your index into expression to be a random number from 0 to the length of the expression array. This will do that.