ZFS snapshot management script

#!/bin/bash
vol="Library" #zfs ZVOL name - I only have one. If you have multiple ZVOLs, you will have to modify this script.
mount="/Library/Snapshot" #mountpoint for snapshots
case $1 in
    list)
        if [ "$2" == "time" ] ; then
            zfs list -t snapshot -o name | grep "$vol"@Auto-H-

        elif [ "$2" == "day" ] ; then
            zfs list -t snapshot -o name | grep "$vol"@Auto-D-

        else
            zfs list -t snapshot -o name

        fi
        ;;

    mount)
        if [ "$2" == "time" ] ; then
            if [ `zfs list -t snapshot -o name | grep "$vol"@Auto-H-$3` ] ; then
                mount -t zfs "$vol"@Auto-H-$3 "$mount"
            else
                echo "ZFS snapshot Auto-H-$3 on ZVOL $vol does not exist. Exiting."
                            exit 2
            fi

        elif [ "$2" == "day" ] ; then
            if [ `zfs list -t snapshot -o name | grep "$vol"@Auto-D-$3` ] ; then
                mount -t zfs "$vol"@Auto-D-$3 "$mount"
            else
                echo "ZFS snapshot Auto-H-$3 on ZVOL $vol does not exist. Exiting."
                                exit 2
                        fi

         elif [ "$2" == "latest"    ; then
                        l=`zfs list -t snapshot -o name | grep "$vol"@Auto-H- | wc -l`
                        snap=`zfs list -t snapshot -o name | grep "$vol"@Auto-H- | sort | tail -n +$l`
                        echo "No snapshot given, mounting most recent snapshot ($snap) at $mount."
                        mount -t zfs "$snap" "$mount"

                else
                        if [ `zfs list -t snapshot -o name | grep "$vol"@$2` ] ; then
                                mount -t zfs "$vol"@$2 "$mount"
                        else
                                echo "ZFS snapshot $2 on ZVOL $vol does not exist. Exiting."
                                exit 2
                        fi

        fi
        ;;

    unmount)
        umount "$mount"

        ;;

    delete)
        if [ "$2" == "time" ] ; then
            if [ `zfs list -t snapshot -o name | grep "$vol"@Auto-H-$3` ] ; then
                read -p "Are you sure you want to delete ZFS snapshot Auto-H-$3 from ZVOL $vol? (y/n) " -n 1 -r
                            echo    # (optional) move to a new line
                            if [[ ! $REPLY =~ ^[Yy]$ ]]
                            then
                                    echo "Operation canceled at user request. Exiting."
                                    exit 1
                            fi
                zfs destroy -r "$vol"@Auto-H-$3
            else
                echo "ZFS snapshot Auto-H-$3 on ZVOL $vol does not exist. Exiting."
                exit 2
            fi

                elif [ "$2" == "day" ] ; then
            if [ `zfs list -t snapshot -o name | grep "$vol"@Auto-D-$3` ] ; then
                                read -p "Are you sure you want to delete ZFS snapshot Auto-D-$3 from ZVOL $vol? (y/n) " -n 1 -r
                                echo    # (optional) move to a new line
                                if [[ ! $REPLY =~ ^[Yy]$ ]]
                                then
                                        echo "Operation canceled at user request. Exiting."
                                        exit 1
                                fi
                                zfs destroy -r "$vol"@Auto-D-$3
                        else
                                echo "ZFS snapshot Auto-D-$3 on ZVOL $vol does not exist. Exiting."
                                exit 2
                        fi

                else
            if [ -n "$2" ] ; then
                if [ `zfs list -t snapshot -o name | grep "$vol"@$2` ] ; then
                                    read -p "Are you sure you want to delete ZFS snapshot $2 from ZVOL $vol? (y/n) " -n 1 -r
                                    echo    # (optional) move to a new line
                                    if [[ ! $REPLY =~ ^[Yy]$ ]] ; then
                                            echo "Operation canceled at user request. Exiting."
                                            exit 1
                                    fi
                                    zfs destroy -r "$vol"@$2
                            else
                                    echo "ZFS snapshot $2 on ZVOL $vol does not exist. Exiting."
                                    exit 2
                            fi
            else
                echo "Invalid Syntax. Exiting."
            fi

                fi
        ;;

        rollback)
                if [ "$2" == "time" ] ; then
            if [ `zfs list -t snapshot -o name | grep "$vol"@Auto-H-$3` ] ; then
                echo "Are you sure you want to roll back ZVOL $vol to ZFS snapshot Auto-H-$3?"
                            read -p "WARNING: This will also delete all snapshots newer than Auto-H-$3 (y/n) " -n 1 -r
                            echo    # (optional) move to a new line
                            if [[ ! $REPLY =~ ^[Yy]$ ]]
                            then
                                    echo "Operation canceled at user request. Exiting."
                                    exit 1
                            fi
                            zfs rollback -r "$vol"@Auto-H-$3
            else
                echo "ZFS snapshot Auto-H-$3 on ZVOL $vol does not exist. Exiting."
                                exit 2
            fi

                elif [ "$2" == "day" ] ; then
            if [ `zfs list -t snapshot -o name | grep "$vol"@Auto-D-$3` ] ; then
                                echo "Are you sure you want to roll back ZVOL $vol to ZFS snapshot Auto-D-$3?"
                                read -p "WARNING: This will also delete all snapshots newer than Auto-D-$3 (y/n) " -n 1 -r
                                echo    # (optional) move to a new line
                                if [[ ! $REPLY =~ ^[Yy]$ ]]
                                then
                                        echo "Operation canceled at user request. Exiting."
                                        exit 1
                                fi
                                zfs rollback -r "$vol"@Auto-D-$3
                        else
                                echo "ZFS snapshot Auto-D-$3 on ZVOL $vol does not exist. Exiting."
                                exit 2
                        fi

                else
                        if [ -n "$2" ] ; then
                                if [ `zfs list -t snapshot -o name | grep "$vol"@$2` ] ; then
                    echo "Are you sure you want to roll back ZVOL $vol to  ZFS snapshot $2?"
                                        read -p "WARNING: This will also delete all snapshots newer than $2 (y/n) " -n 1 -r
                                        echo    # (optional) move to a new line
                                        if [[ ! $REPLY =~ ^[Yy]$ ]] ; then
                                                echo "Operation canceled at user request. Exiting."
                                                exit 1
                                        fi
                                        zfs rollback -r "$vol"@$2
                                else
                                        echo "ZFS snapshot $2 on ZVOL $vol does not exist. Exiting."
                                        exit 2
                                fi
                        else
                                echo "Invalid Syntax. Exiting."
                        fi

                fi
                ;;


    *)
        zfs list -t snapshot -o name
        ;;
esac