判断目录是否存在

#!/bin/sh
if [ -d "/mnt/backup" ]; then
    echo '存在'
else
    echo '不存在'
fi

判断目录是否为挂载点

#!/bin/sh
if mount | grep /mnt/backup > /dev/null; then
    echo '是挂载点！'
else
    echo '备用盘未挂载！'
fi

参考

• https://www.cnblogs.com/37yan/p/6962563.html
• https://stackoverflow.com/questions/9422461/check-if-directory-mounted-with-bash