When you’re done wiring (or not wiring, as the case may be), your network is ready. Your Mac should “see” any Ethernet or shared USB printers, in readiness to print (Chapter 9). You can now play network games or use a network calendar. And you can now turn on File Sharing, one of the most useful features of all.
In File Sharing, you can drag files back and forth between different Macs (or even Windows PCs) on the network, exactly as though the other computer’s folder or disk is a hard drive connected to your own machine. You can see the idea in Figure 14-2.
The thing is, it’s not easy being Apple. You have to write one operating system that’s supposed to please everyone, from the self-employed first-time newbie to the network administrator for NASA. You have to design a networking system simple enough for the laptop owner who just wants to copy things to a desktop Mac when returning from a trip, yet secure and flexible enough for the network designer at a large corporation.
Clearly, different people have different attitudes toward the need for security and flexibility.
That’s why OS X offers three ways to share files, striking three different positions along the Simplicity-to-Flexibility Spectrum:
The easiest way: AirDrop. This feature is dreamy—if there are other people in your house or office who have wireless Macs running Lion or Mountain Lion. Imagine this: You open the AirDrop folder, where you see everybody else’s icons. To give someone a file, you drop its icon on that person’s face. Done.
What used to be the easiest way: the Public folder. Every account holder has a Public folder. It’s free for anyone else on the network to access. Like a grocery store bulletin board, there’s no password required. Super-convenient, super-easy.
There’s only one downside, and you may not care about it: You have to move or copy files into the Public folder before anyone else can see them. Depending on how many files you want to share, this can get tedious, disrupt your standard organizational structure, and eat up disk space.
The flexible way: any folder. You can also make any file, folder, or disk available for inspection by other people on the network. This method means that you don’t have to move files into the Public folder, for starters. It also gives you elaborate control over who is allowed to do what to your files. You might want to permit your company’s executives to see and edit your documents, but allow the peons in Accounting just to see them. And Andy, that unreliable goofball in Sales? You don’t want him even seeing what’s in your shared folder.
Of course, setting up all those levels of control means more work and more complexity.
The following pages tackle these three methods one at a time.
Figure 14-2. Here’s the master switch that makes your Public folder (and any other folders you designate) available to other people on the network. You can edit the Computer Name, if you like. Your Mac will appear on the network with this name. Make it nice and descriptive, such as Front Desk iMac.
AirDrop is one of Mountain Lion’s star attractions. It’s a breakthrough in speed, simplicity, and efficiency. There’s no setup, no passwords involved. It lets you copy files to someone else’s Mac up to 30 feet away, instantly and wirelessly; you don’t need an Internet connection or even a WiFi network. It works on a flight, a beach, or a sailboat in the middle of the Atlantic. It also works if you are on a WiFi network, doing other things online.
Figure 14-3. Top: If there are other Lion or Mountain Lion Macs within about 30 feet, you see their logged-in users’ icons here. Usually, the icons display the Mac owners’ account pictures; but if they have facial photos in your Contacts, then you see those instead. Bottom: Here’s what you see if you’re the recipient (and have clicked Save in the confirmation box). To find your newly arrived goodies, open your Downloads folder.
To give someone a file, you and your lucky recipient must each open your respective AirDrop window. Then you have a choice:
Open the AirDrop window. To do that, click the AirDrop icon (at the top of the Sidebar in any Finder window), choose Go→AirDrop, or press Shift-⌘-R.
Note
If you don’t see AirDrop in the Sidebar, and you’re sure you’re using Lion or Mountain Lion, it’s because somebody turned off its checkbox in Finder→Preferences→Sidebar. Hiding the AirDrop icon in this way means you can’t use the feature at all, at least not by dragging an icon into a window. You can still use the Share button as described below.
The window shown in Figure 14-3 appears. After a moment, it fills up with icons for everyone nearby who’s running a wireless Lion or Mountain Lion Mac—and has opened their AirDrop windows. They don’t have to do anything else; their icons show up automatically in your AirDrop window.
Now drag a file or folder icon, or several, onto the icon of the intended recipient. When the Mac asks if you’re sure, click Send or press Return.
The recipient now sees a message that says, “[Other guy’s Mac] wants to send you [the file’s name].” And there are three options: Save and Open, Decline, and Save.
If the lucky winner clicks one of the Save buttons, then the file transfer proceeds automatically. A progress bar wraps around the other person’s icon in the AirDrop window—cute. The transfer is encrypted, so evildoers nearby have no clue what you’re transferring (or even that you’re transferring).
The file winds up in the other guy’s Downloads folder.
In Mountain Lion, there’s another, more direct way to send a file by AirDrop. Click the icon of the file you want to send (or select several). Now choose the Share→AirDrop command.
And where is that command? Everywhere. It’s in the
shortcut menu that appears when you right-click an icon. It’s in
the 
icon at the top of every Finder window, and
at the top of every Quick Look window. (See The Mountain Lion Share Button for more on the Share
button.)
Now a miniature version of the AirDrop window appears; see Figure 14-4.
Once you’ve clicked the recipient’s icon, and the recipient agrees to receive (by clicking Save and Open, or Save), the transfer begins, just as described above.
Figure 14-4. The icons of nearby AirDrop-happy Macs show up in this fun-sized version of the regular AirDrop window. You’ve already said which files you want to send; now you just have to specify who gets them. Click the Mac’s icon and then click Send.
All right. So if AirDrop is so great, why doesn’t it wipe out all other forms of file transfer and save this book a bunch of pages? Because (a) it works only on Macs running Lion or Mountain Lion, (b) it works only wirelessly, and (c) it’s a one-way street. Other people can’t take files from your Mac—you have to shove the files to them.
Note
Actually, there’s another limitation: AirDrop doesn’t work on some older Macs. It works on the MacBook Pro (made since late 2008), MacBook Air (late 2010), MacBook (late 2008), iMac (early 2009), Mac mini (mid-2010), and Mac Pro (mid-2010).
If you can get past those limitations, though, there’s a lot of great stuff in AirDrop:
If you see someone’s name beneath her icon in the AirDrop window, that means that she’s in your Contacts and has signed in with her Apple ID. That’s an extra bit of confidence that she is who her icon says she is.
AirDrop works by creating a temporary two-computer wireless network. That’s why it works even if you’re not in a WiFi hotspot. It does, however, require both computers to have WiFi turned on, which you can check by opening the
menu.If you’re the one receiving a file, you can cancel a half-finished transfer by clicking the
button on the progress bar that wraps around the
sender’s icon in the AirDrop window. (Another way: If your
Downloads folder is set to Stack view, you can click the
button in the corner of the file’s
icon.)AirDrop doesn’t work unless both of you have opened your AirDrop windows in the Finder. If you close your AirDrop window, or even click outside that window, your Mac disappears from everyone else’s AirDrop screens.
AirDrop is the simplest and happiest way to share files, no doubt about it. But it requires Lion/ Mountain Lion on both Macs, it works only wirelessly, and it’s a one-way street (you have to initiate the file handoff).
The next simplest file-sharing method eliminates all those limitations. It’s the Public-folder method.
Inside your Home folder, there’s a folder called Public. (Inside everybody’s Home folder is a folder called Public.)
Anything you put into this folder is automatically available to everyone else on the network. They don’t need a password, they don’t need an account on your Mac—they just have to be on the same network, wireless or wired. They can put files here or copy things out.
To make your Public folder available to your networkmates, you
have to turn on the File Sharing master switch. Choose 
→System Preferences, click Sharing, and then turn on File Sharing (as shown back in Figure 14-2).
Now round up the files and folders you want to share with all comers on the network and drag them into your Home→Public folder. That’s all there is to it.
Note
You may notice that there’s already something in your Public folder: a folder called Drop Box. It’s there so that other people can give you files from across the network, as described later in this chapter.
So now that you’ve set up Public folder sharing, how are other people supposed to access your Public folder? See Accessing Shared Files.
If the Public-folder method seems too simple and restrictive, then you can graduate to the “share any folder” method. In this scheme, you can make any file, folder, or disk available to other people on the network.
The advantage here is that you don’t have to move your files into the Public folder; they can sit right where you have them. And this time, you can set up elaborate sharing privileges (also known as permissions) that grant individuals different amounts of access to your files.
This method is more complicated to set up than that Public-folder business. In fact, just to underline its complexity, Apple has created two different setup procedures. You can share one icon at a time by opening its Get Info window; or you can work in a master list of shared items in System Preferences.
The following pages cover both methods.
Here’s how to share a Mac file, disk, or folder disk using its Get Info window.
The following steps assume that you’ve turned on
→System Preferences→Sharing→File Sharing, as shown in Figure 14-2.
Highlight the folder or disk you want to share. Choose File→Get Info.
The Get Info dialog box appears (Figure 14-5). Expand the General panel, if it’s not already visible.
Note
Sharing an entire disk means that every folder and file on it is available to anyone you give access to. On the other hand, by sharing only a folder or two, you can keep most of the stuff on your hard drive private, out of view of curious network comrades. Sharing only a folder or two does them a favor, too, by making it easier for them to find the files they’re supposed to have. This way, they don’t have to root through your entire drive looking for the folder they actually need.
Enter your administrative password, if necessary.
Expand the Sharing & Permissions panel, if it’s not already visible. Click the
icon and enter
your administrator’s password.The controls in the Sharing & Permissions area spring to life and become editable. At the bottom of the Info panel is a little table. The first column can display the names of individual account holders, like Casey or Chris, or groups of account holders, like Everyone or Accounting Dept.
The second column lists the privileges each person or group has for this folder.
Now, the average person has no clue what “privileges” means, and this is why things get a little hairy when you’re setting up folder-by-folder permissions. But read on; it’s not as bad as it seems.
Edit the table by adding people’s names. Then set their access permissions.
At the moment, your name appears in the Name column, and it probably says Read & Write in the Privilege column. In other words, you’re currently the master of this folder. You can put things in, and you can take things out.
If you just want to share files with yourself, so you can transfer them from one computer to another, you can stop here.
If you want to share files with other people—well, at the moment, the privileges for Everyone are probably set to “Read only.” Other people can see this folder, but they can’t do anything with it.
Your job is to work through this list of people, specifying how much control each person has over the file or folder you’re sharing.
Figure 14-6. This list includes every account holder on your Mac, plus groups you’ve set up, plus the contents of your address book. One by one, you can add them to the list of lucky sharers of your files or folders—and then change the degree of access they have to the stuff you’re sharing.
To add the name of a person or group, click the
button below the list. The list shown
in Figure 14-6
appears.Now click a name in the list. Then, from the Privilege pop-up menu, choose a permissions setting.
Read & Write has the most access of all. This person, like you, can add, change, or delete any file in the shared folder, or make any changes she likes to a document. Give Read & Write permission to people you trust not to mess things up.
Read only means “Look, but don’t touch.” This person can see what’s in the folder (or file) and can copy it, but he can’t delete or change the original. It’s a good setting for distributing company documents or making source files available to your minions.
Write only (Drop Box) means that other people can’t even open the folder. They can drop things into it, but it’s like a mail slot: The letter disappears into the slot, and then it’s too late for them to change their minds. As the folder’s owner, you can do what you like with the deposited goodies. This drop-box effect is great when you want students, coworkers, or family members to be able to turn things in to you—homework, reports, scandalous diaries—without running the risk that someone else might see those documents. (This option doesn’t appear for documents — only disks and folders.)
No access is an option only for Everyone. It means that other people can see this file or folder’s icon but can’t do a thing with it.
Close the Get Info window.
Now the folder is ready for invasion from across the network.
It’s very convenient to turn on sharing one folder at a time, using the Get Info window. But there’s another way in, too, one that displays all your shared stuff in one handy master list.
To see it, choose →System Preferences. Click Sharing. Click File Sharing (and make sure it’s turned on).
Now you’re looking at a slightly different kind of permissions table, shown in Figure 14-7. It has three columns:
Shared folders. The first column lists the files, folders, and disks you’ve shared. You’ll probably see that every account’s Public folder is already listed here, since they’re all shared automatically. (You can turn off sharing for a Public folder, too, just by clicking it and then clicking the
button.)But you can add more icons to this list. Either drag them into the list directly from the desktop or a Finder window, or click the
sign, navigate to the item you want to
share, select it, and then click Add. Either way, that item
now appears in the Shared Folders list.Users. When you click a shared item, the second column sprouts a list of who gets to work with it from across the network. You’re listed here, of course, since it’s your stuff. There’s also a listing here for Everyone, which really means, “everyone else”— that is, everyone who’s not specifically listed here.
You can add to this list, too. Click
to open the person-selection box shown
in Figure 14-6. It
lists the other account holders on your Mac, and some
predefined groups, as well as the contents of your
Contacts.Note
Most of the Contacts people don’t actually have accounts on this Mac, of course. If you choose somebody from this list, you’re asked to make up an account password. When you click Create Account, you’ve actually created a Sharing Only account on your Mac for that person, as described on Managed accounts with Parental Controls. When you return to the Accounts pane of System Preferences, you’ll see that new person listed.
Double-click a person’s name to add her to the list of people who can access this item from over the network, and then set up the appropriate privileges (described next).
To remove someone from this list, just click the name and then click the
button.Users. This third column lets you specify how much access each person in the second column has to this folder. Your choices, once again, are Read & Write (full access to change or delete this item’s contents); Read Only (open or copy, but can’t edit or delete); and Write Only (Drop Box), which lets the person put things into this disk or folder, but not open it or see what else is in it.
For the Everyone group, you also get an option called No Access, which means that this item is completely off limits to everyone else on the network.
And now, having slogged through all these options and permutations, your Mac is ready for invasion from across the network.