if [ "$A" != "$B" ]; then ----- ②
    echo "!= operator: True"
else
    echo "!= operator: False"
fi

if [ "$A" \> "$B" ]; then ----- ③
    echo "> operator: True"
else
    echo "> operator: False"
fi

if [ -n "$A" ]; then ---------- ④
    echo "-n operator: True"
else
    echo "-n operator: False"
fi

if [ -z "$A" ]; then ---------- ⑤
    echo "-z operator: True"
else
    echo "-z operator: False"
fi