12.13.4 Quitting Ediff
When you're done comparing the files, the quickest way to close the control window and get back to the "normal" Emacs world is to type q to quit your Ediff session. After confirming that you really want to do this, Ediff closes the control window and cleans up after itself. You can also suspend the session temporarily by typing z for suspend. This closes the Ediff control window, but Ediff remembers that you were in the middle of a session, to which you can return later whenever you'd like. The easiest way to do this is to view the list of active Ediff sessions by choosing Tools → Ediff Miscellanea → List Ediff Sessions. When you actually quit an Ediff session, it no longer appears in this list.
12.13.5 Recovering from Confusion
If you've been cruising along in Ediff and suddenly find your commands aren't working, you've probably accidentally clicked on the differences window and are typing in one of the buffers directly, or perhaps you used an Ediff command that switched the window focus on you unexpectedly. Make sure to undo the stray characters you've typed into the comparison buffer, then click on the control window and start issuing commands again.
Of course, you may want to intentionally jump over to edit one of the buffers as you notice changes you'd like to make. You can do that at any time; just remember to switch back to the control window when you want move to other differences or use other Ediff commands. If, after editing one of the comparison buffers for a while, you'd like to return to viewing differences, starting with the difference nearest to your edit location, click in the control window and type g followed by the letter assigned to the buffer in which you're interested (as discussed earlier in "Making Changes").
If you've made substantial changes by editing the buffer directly, you may find that the difference region highlights have drifted out of synch with the actual location of differences. To fix this, once the control window has focus, type ! to cause Ediff to recalculate and redisplay the differences.
If you've reconfigured the buffers you're looking at (perhaps you wanted to look up some help text, or engage in a side task, which Emacs certainly encourages) you can restore the window configuration for Ediff by clicking on the control window and typing C-l (recenter). This sets up the comparison window to display the files you're comparing and centers the current difference in each buffer. You may find that it also causes the comparison window to get keyboard focus, so be sure to click on the control window if necessary before you try to issue any Ediff commands.
12.13.6 Learning More
As noted, there is a whole lot more to Ediff than we can discuss here. When you want to explore it, a good starting place is the built-in Ediff manual. You can get to this by typing E (Shift-e, the capitalization matters) in the Ediff control window. If you're not already inside Ediff, you can choose Tools → Ediff Miscellanea → Ediff Manual, or you can invoke Info, the Emacs documentation browser, by typing C-h i, and choose Ediff from the main menu of topics. (Typing m for menu, followed by e d Enter is enough to complete "Ediff" and jump to its manual.)
For more task-specific help, you can click on any of the commands in the quick help window using your middle mouse button to get help describing what it does. (If you lack a three button mouse, you can click on the command with your regular mouse button and then press Enter.)
12.13.7 Customizing Ediff
By now it should come as no surprise that you can change many details about the way that Ediff works so it better fits your way of thinking and working. After you've got a good grasp of the basics, you can use the Custom facility described in Chapter 10 to tweak the way Ediff works by choosing Tools → Ediff Miscellanea → Customize Ediff. If the use of a separate operating system window (frame) for the control window is driving you batty, you can toggle that behavior right away by choosing Tools → Ediff Miscellanea → Toggle use of separate control buffer frame.
12.13.8 Invoking Ediff Automatically
If Ediff is so powerful, why isn't it the default mode used by the vc-diff command? The most likely explanation is historical; vc-diff has been around longer than Ediff, and it would have been disruptive to long-standing users of Emacs if a strange new interface was unexpectedly foisted on them. It seems people are writing patches to integrate Ediff more tightly with VC, but they are not (yet?) part of the Emacs distribution. If you're interested in the current state of any of these efforts, try a Google search for "vc ediff."
Chapter 13. Platform-Specific Considerations
In this chapter, we describe installing Emacs on Unix, Mac OS X, and Windows as well as some of the subtleties of running Emacs on the latter two platforms.
Emacs 21 runs on free Unix systems including Linux and BSD variants as well as on commercial Unix versions such as AIX, Solaris, SunOS,` and Ultrix. It runs on Mac OS X (currently a separate fork, but due to be folded into the main distribution starting with 21.4). It runs on Windows and even on MS-DOS. You can still get ports for Mac OS 8/9 and Amiga (to name only a few). Emacs is truly a multiplatform editor.
We cover installing Emacs on Unix, Mac OS X, and Windows. For Windows and Mac OS X, prebuilt binaries are available. You may want to build Emacs from source in order to obtain the latest version. However, we have found up-to-date binaries online for Windows and Mac OS X; you just have to scout around on the Net to find them. By the time you read this, the sources for the binaries that we cite may be out of date. Check out this book's web site for updated links in that case (http://www.oreilly.com/catalog/gnu3).
A related issue is where to get Emacs. The Free Software Foundation (FSF) is the official source for Emacs, but like most software organizations, official releases are few and far between. Often, building Emacs from CVS sources is the best way to get a leading-edge version. Only you can decide whether you would rather have the latest features—along with some bugs—or download the tried-and-true version from the FSF's site.
13.1 Emacs and Unix
Emacs was originally built on a Unix system and continues to run on the multitude of Unix variants out there. We're going to download the latest source and show you how to build Emacs from scratch. It's not really that hard and it has the salutary effect of keeping you up-to-date with future releases.
13.1.1 Where to Get Emacs?
If you can't wait, the primary source for downloading Emacs is http://ftp.gnu.org/pub/gnu/emacs/. Alternatively, you can use CVS to nab the absolute latest build. But more on that in a minute.
13.1.1.1 Downloading Emacs from the Web
You can get Emacs from any one of many sites—as long as your Internet connection is fast enough to transfer a 20 MB file easily. You must also have at least 120 MB of disk space free; this number will certainly grow in future Emacs releases.