test_string ()
{
if (( $# != 1 ))
then
     echo 'ERROR'
     return
fi

C_STRING=$1

# Test the character string for its composition

case $C_STRING in

     +([0-9])) echo 'POS_INT' # Integer >= 0
               ;;
     +([-0-9])) echo 'NEG_INT' # Integer < 0
               ;;
     +([a-z])) echo 'LOW_CASE' # lower case text
               ;;
     +([A-Z])) echo 'UP_CASE' # UPPER case text
               ;;
     +([a-z]|[A-Z])) echo 'MIX_CASE' # MIxed CAse text
               ;;
            *) echo 'UNKNOWN' # Anything else
               ;;
esac
}