Why on Earth would any red-blooded MacBook owner want to leave the comfort of the trackpad to use a keyboard? After all, the graphical user interface is what made the Macintosh great in the first place. With the Finder, you can navigate and manage the various files on your hard drive with a few clicks. This sounds simple enough, but for some tasks, using the keyboard can be just as fast, if not faster.

Suppose, for example, that you need to copy a file from somewhere on your hard drive to somewhere else on that same drive. To do so with the Finder, you must first open a Finder window (by clicking the Finder icon in the Dock or by double-clicking a drive icon on your Desktop). Then, by using a succession of trackpad clicks, you navigate to where the file that you wish to copy resides. Next, you might open another Finder window and navigate to the folder where you wish to copy the file. (Note that opening the second Finder window requires pressing

Comparatively, by using the keyboard and the power of UNIX, you can accomplish the same task with a one-line command. For some tasks, your trackpad (or a USB mouse) is definitely the way to go, but you can perform some other tasks just as quickly, if not faster, with the keyboard. For the skinny on one-line commands, skip down to the upcoming section "Uncovering the Terminal."

So maybe you're not an expert typist, and using the trackpad still sounds inviting. For many scenarios, you'd be correct in assuming that a "pointing thing" can handle the job just as quickly and easily as a bunch of commands that you have to memorize. Using the keyboard, however, offers some other distinct advantages over the trackpad. To allow you to control your computer from the keyboard, all UNIX operating systems offer the command line tool. With this tool, you can enter commands one line at a time: hence, its name. Mac OS X ships with the command line application, Terminal. You can find it here:

/Applications/Utilities/Terminal

One shining feature of the command line is its efficiency. To wit: When you use a trackball or mouse, one click is equal to one command. When you use the command line, on the other hand, you aren't limited to entering one command at a time; rather, you can combine commands into a kind of super-command (minus the silly cape, but with bulging muscles intact), with each command performing some action of the combined whole. By using the command line, you can string together a whole bunch of commands to do a very complex task.

For example, consider how many times you'd have to click in the Finder to do the following:

By using the command line, you could accomplish all these tasks by typing only one super-command: that is, a collection of three simple commands combined to form one instruction. The built-in Terminal program that ships with Mac OS X Snow Leopard gives you everything that you need to start using the command line. I show you how in the section "Uncovering the Terminal," later in this chapter.

The Finder is generally a helpful thing, but it makes many assumptions about how you work. One of these assumptions is that you don't have any need to handle some of the files on your hard drive. As I mention in Book III, Chapter 6, Mac OS X ships with its system files marked Off Limits, and I generally agree with that policy (which keeps anyone from screwing up the delicate innards of Mac OS X). To secure your system files, Apple purposely hides some files from view.

But what road do you take if you actually need to view or modify those system files? Yep, you guessed it: The command line comes to the rescue! You can use the command line to peer inside every nook and cranny of your MacBook's vast directory structure on your hard drive. It also has the power to edit files that aren't normally accessible to you. With the command line, you can pretend to be other users — even users with more permissions. By temporarily acting as another more powerful user, you can perform actions with the command line that would be impossible in the Finder. (Just remember to make sure that you know exactly what you're doing, or you're working with an Apple technical support person — a wrong move, and it'll be time for an Ominous Chord.)

If all these benefits are beginning to excite you, hold on to your socks! Not only can you perform complex commands with the command line, you can go even one step further: automation. If you find yourself using the same set of commands more than once, you're a likely candidate for using automation to save time. Instead of typing the list of commands each time, you can save them to a text file and execute the entire file with only one command. Now that's power, right up there with the dynamic duo of AppleScript and Automator!

Of course, you probably don't like doing housekeeping tasks while you're busy on other things, so schedule that list of commands to run in the middle of the night while you're fast asleep. UNIX lets you do that, too, using the launchd command.

"So, Mark, the command line is the cat's meow for efficiently accessing and working with files on my MacBook, and I can use it to automate many operations. Anything else?" I'm glad you asked! By using the command line, you can also send commands to another computer anywhere in the world (as long as you know the right login and password). After you log into another computer, you can use the same commands for the remote computer.

UNIX was created with multiple users in mind. Because computers used to be expensive (and honking huge machines to boot), UNIX was designed so that multiple users could remotely use the same machine simultaneously. In fact, if Mac OS X is your first encounter with UNIX, you might be surprised to know that many UNIX beginners of the past weren't even in the same room, building, state, or even country as the computer that they were using.

Not only can you work with a computer that's in a different physical location, but it's also very fast to do so. Instead of the bandwidth hog that is the Internet, the command line is lean and mean. This permits you to use a remote computer nearly as fast as if it were sitting on the desk in front of you. (This is a great advantage for road warriors who need to tweak a Web or an e-mail server from a continent away.)

Upon launch of the Terminal application, you'll immediately notice some text in the window that appears on-screen:

Last login: Sun Jun 23 17:51:14 on console
WHITEDRAGON:~; markchambers$

As you might guess, this text details the last time that you logged into the Terminal. The last line, however, is the more important one. It's called the prompt.

The prompt serves some important functions. First, it lists the current directory, which is listed as ~. A tilde character (~) denotes a user's Home directory. By default, you're always in your Home folder each time you begin a new session on the Terminal. After the current directory, the Terminal displays the name of the current user, which is markchambers in this example.

The final character of the prompt is a $. Consider this your cue because immediately after this character is where you enter any command that you wish to execute. Go ahead; don't be shy. Try out your first command by typing uptime in the Terminal application. (It's a good idea to type UNIX commands in lowercase.) Your text appears at the location of the cursor, denoted by a small square. If you make a mistake while entering the command, press the Delete key to back up and then type the characters again. (If the typing error is stuck deep in a longer command, press the left- or right-arrow key to move the cursor immediately after the incorrect character and press Delete to back up; then type the correct characters.) After you type the command, press Return to execute it.

WHITEDRAGON:~ markchambers$ uptime
6:24PM  up  2:42, 4 users, load averages: 2.44, 2.38, 1.90
WHITEDRAGON:~ markchambers$

If all goes well, you should see a listing of how long your Mac has been running since the last reboot or login. In the example listing, the computer has been running for 2 hours and 42 minutes (2:42 in line 2). Simple, eh? Immediately following the listing of the uptime command, the Terminal displays another prompt for you to enter more commands. I examine many more commands later in this chapter.

Using the command line is simply a matter of entering simple instructions — or commands — into the Terminal application and pressing Return to execute them. It's easy to use the command line to navigate through the various folders on your hard drive. You'll become accustomed to using two vital commands: ls and cd. The ls command is shorthand for list, and it does just that: It lists the contents of the current directory. Enter ls at your prompt, and you should see a listing of your Home folder.

The complementary cd command (lowercase) — which incidentally stands for change directory — opens any folder that you specify. It works much the same as double-clicking a folder in the Finder: The difference is that following the cd command, you don't immediately see all the folder's content. However, the cd command requires a parameter (extra options or information that appear after the command) so that your Mac knows which folder to open.

For example, to open the Documents folder that resides in your Home directory, type cd Documents and press Return. When you do, you might be surprised to see another prompt displayed immediately. So where are all the files in the Documents folder? You must enter another command to see what items are in the folder that you just opened. Type ls again to see the contents of the Documents folder.

cd "My Picture Folder"

Read more about using quotation marks in your commands in the upcoming section "Command-line gotchas."

To return to your Home folder in this example, enter a modified version of the cd command:

cd ..

This causes your MacBook to move back up the folder hierarchy one folder, in this case to your Home directory. By using these three simple commands — ls, cd foldername, and cd .. — you can traverse your entire hard drive.

Just because the Terminal is text based doesn't mean that it doesn't act like a good Macintosh citizen. All the usual Mac features that you know and love are there for you to use. Copy and Paste functions work as you might expect — but only at the prompt position.

Drag-and-drop is also at your disposal. After you play around with the Terminal for a while, you'll find yourself bored to tears typing the long paths that represent the files on your hard drive. To automatically enter the path of a file or folder to a command, simply drag it to the active Terminal window, as shown in Figure 1-2. The file's full path instantly appears at the location of your cursor. (Thanks, Apple!)

Figure 1.2. Drag a file from a Finder window into Terminal to display its path.

You can even use the mouse while entering commands in the Terminal. Click and drag your mouse over text to select it. From there, you can copy to the Clipboard as you might expect with any other application.

UNIX commands can perform many amazing feats. Despite their vast abilities, all commands follow a similar structure:

command <optional flag(s)> <optional operand(s)>

The simplest form of a UNIX command is the command itself. (For a basic discussion on UNIX commands such as ls, see the earlier section, "A few commands to get started.") You can expand your use of the ls command by appending various flags, which are settings that enable or disable optional features for the command. Most flags are preceded by a dash (-) and always follow the command. For instance, you can display the contents of a directory as a column of names (complete with file details) by tacking on a -l flag to the ls command.

ls −l

Besides flags, UNIX commands sometimes also have operands. An operand is something that is acted upon. For example, instead of just entering the ls command, which lists the current directory, you can add an operand to list a specific directory:

ls ~/Documents/myProject/

Sometimes a command can take multiple operands, as is the case when you copy a file. The two operands represent the source file and the destination of the file that you want to copy, separated by a space. The following example copies a text file from the Documents folder to the Desktop folder by using the cp command (short for copy).

cp ~/Documents/MyDocument ~/Desktop/MyDocument

You can also combine flags and operands in the same command. This example displays the contents of a specific folder in list format:

ls −l ~/Documents/myProject/

In earlier sections, I describe a few simple command-line functions. All these commands have something in common: You might not have noticed, but every example thus far involved folder names and filenames that contained only alphanumeric characters. Remember what happens if you have a folder name that has a space in it? Try the following example, but don't worry when it doesn't work.

cd /Desktop Folder

The result is an error message:

-bash: cd: /Desktop: No such file or directory

The problem is that a space character isn't allowed in a path. To get around this problem, simply enclose the path in double quotation marks, like this:

cd "/Desktop Folder"

In a similar vein, you can get the space character to be accepted by a command by adding an escape character. To escape a character, add a backslash () immediately prior to the character in question. To illustrate, try the last command with an escape character instead. Note that this time, no quotation marks are necessary.

cd /Desktop Folder

By now, you might be wondering how a computer techno-wizard is supposed to keep all these commands straight. Fortunately, you can find generous documentation for nearly every command available to you. To access this built-in help, use the man command. Using the man command (shorthand for manual) will display a help file for any command that it knows about. For example, to read the available help information for the ls command, simply type man ls at the prompt. Figure 1-3 illustrates the result.

Figure 1.3. Use the man command to display help information.

To speed things along, the bash shell can automagically complete your input for you while you type. Although the Terminal permits you to enter commands via the keyboard, it is the shell that interprets those commands. Many kinds of shells are available to UNIX users. The shell that Snow Leopard uses by default is bash — another common shell is tcsh. Use the autocompletion features of bash to autocomplete both commands and filenames. To demonstrate, begin by typing the following:

cd ~/De

Then press the Tab key. The result is that the shell predicts that you will want to type

cd ~/Desktop/

Of course, if you have another folder that begins with the letters De in the same folder, you might need to type a few additional characters. This gives the autocompletion feature more information to help it decide which characters you want to type. In other words, if you don't type enough characters, autocompletion ends up like a detective without enough clues to figure things out.

Before you dive into UNIX commands, you should first know a few facts ...nasty things, facts, but you can't earn your pair of techno-wizard suspenders without 'em. For starters, as a Mac user, you might not be familiar with how paths work in UNIX. A path is simply a textual representation of a folder or file. The simplest path is your Home directory, which is denoted by a tilde character (~) — the tilde character acts as the equivalent of /Users/<your short account name (in my case, /Users/markchambers). Any folder within the Home directory is represented by the folder's name preceded by a forward slash (/). For example, a document entitled myDoc that resides in the current user's Documents folder would have a path like this:

~/Documents/myDoc

Similarly, a folder named myFolder that resides in the current user's Documents folder would have a path like this:

~/Documents/myFolder/

Because Mac OS X is a multiuser environment — and your applications and files may be located in many different folders across your hard drive — you will want to work with folders or files somewhere other than in your Home folder. Starting from your Home folder, enter the following command:

cd ..

This moves you to the folder right above your Home folder, which happens to be the Users folder. Using another quick ls command will show you all users who are permitted to use the machine. (By the way, Shared isn't a user — it's a folder with privileges set so that any user can access its contents.)

Enter cd .. once again, and you find yourself at the root of your main hard drive. The root directory is what you see in the Finder when you double-click your hard drive icon on the Desktop. A user's Home directory is represented by a tilde character (~), and the root of the hard drive is denoted by a forward slash (/), as displayed by the prompt:

WHITEDRAGON:/ markchambers$

It's easy to return to your Home directory by following this sequence:

WHITEDRAGON:/ markchambers$ cd Users
WHITEDRAGON:/Users markchambers$ cd markchambers
WHITEDRAGON:~ markchambers$

Here's a faster way. Instead of moving through each successive folder until you reach your intended destination, you can specify the path by using just one cd command:

WHITEDRAGON:/ markchambers$ cd /Users/markchambers
WHITEDRAGON:~ markchambers$

Furthermore, when you navigate your hard drive by using paths, you can jump directly to your desired destination from any place. When you enter cd .., it is in relation to your current position, whereas entering

cd /Users/markchambers

will always take you to the same directory, regardless of your starting point.

After you're comfortable with moving around the hierarchy of your hard drive, it's a cinch to copy, move, and rename files and folders.

To copy files from the command line, use the cp command. Because using the cp command will copy a file from one place to another, it requires two operands: first the source and then the destination. For instance, to copy a file from your Home folder to your Documents folder, use the cp command like this:

cp ~/MyDocument ~/Desktop/MyDocument

WHITEDRAGON:~ markchambers$ cp ~/Desktop/MyDocument /Users/fuadramses/Desktop/MyDocument

Denied! Thwarted! Refused!

cp: /Users/fuadramses /Desktop/MyDocument: Permission denied

If you can't copy to the destination that you desire, you need to precede the cp command with sudo. Using the sudo command allows you to perform functions as another user. The idea here is that the other user whom you're "emulating" has the necessary privileges to execute the desired copy operation. When you execute the command, the command line asks you for a password. If you don't know what the password is, you probably shouldn't be using sudo. Your computer's administrator should have given you an appropriate password to use. After you enter the correct password, the command executes as desired.

sudo cp ~/Desktop/MyDocument /Users/fuadramses/Desktop/MyDocument
Password:

A close cousin to the cp (copy) command is the mv (move) command. As you can probably guess, the mv command moves a folder or file from one location to another. (I told you that all this character-based stuff would start to make sense, didn't I?) To demonstrate, this command moves MyDocument from the Desktop folder to the current user's Home folder:

mv ~/Desktop/MyDocument ~/MyDocument

Ah, but here's the hidden surprise: The mv command also functions as a rename command. For instance, to rename a file MyDocument on the Desktop to MyNewDocument, do this:

mv ~/Desktop/MyDocument ~/Desktop/MyNewDocument

In this case, you can see that the mv command is really copying the original file to the destination and then deleting the original. Because both folders in this example reside in the same folder (~/Desktop/), it appears as though the mv command has renamed the file.

Again, like the cp command, the mv command requires that you have proper permissions for the action that you want to perform. Use the sudo command to perform any commands that your current user (as displayed in the prompt) isn't allowed to execute. On UNIX systems, not all users are necessarily equal. Some users can perform functions that others can't. This is handy for keeping your child's mitts off important files on your laptop. It also creates a hurdle should you choose to work on files while using your child's restricted user account. The sudo command lets you temporarily become another user — presumably one that has permission to perform some function that the current user can't.

What would file manipulation be without the ability to delete files? Never fear; UNIX can delete anything that you throw at it. Use the rm (short for remove) or rmdir (short for remove directory) command to delete a folder or file. For example, to delete MyNewDocument from the Desktop folder, execute the rm command like this:

rm ~/Desktop/MyNewDocument

Launching applications and opening documents is child's play for a UNIX pro like you. The open command does it all. For example, to bring the Finder to the foreground without touching the mouse, use

open /System/Library/CoreServices/Finder.app

To open a document from the command line, follow a similar scheme. For example, to view an image named myImage.tif that's stored in your Documents folder using the default application (typically Preview), try this:

open ~/Documents/myImage.tif

One of my favorite command-line functions is the cal command, which displays a calendar in text form. Simply entering cal at the prompt displays a calendar for the current month, as shown in Figure 1-4.

Figure 1.4. Type cal to view a calendar for the current month.

Append a number to the cal command to display a 12-month calendar for that year. The number that follows the cal command is the year for which you'd like to see a calendar. For example, to view a calendar for 1970, type cal 1970. The result appears in Figure 1-5.

Append a month number and a year number to display the calendar for that month. For example, to view a calendar for April 2010, type cal 04 2010.

Another useful command that's related to the cal command is date. Type date at the command line to display the day, date, time, and year based on your computer's settings.

WHITEDRAGON:~ markchambers$ date
Mon Jan 15 11:32:20 CDT 2009

Figure 1.5. Type cal followed by a year to view the 12 months of that year.

Have you ever been curious as to why your hard drive seems to spin and grind on occasion while your system is seemingly inactive? Mac OS X sometimes has a lot of stuff going on behind the scenes. To discover just what your computer is busy doing at any time, use the top command to display all the actions that your computer is currently performing, as shown in Figure 1-6. These activities are called processes; some are created when you launch applications, and others are simply tasks that Mac OS X has to take care of to keep things running smoothly.

Besides listing the names of the various processes currently in use, top tells you how much of your CPU is being devoted to each process. This lets you know what process is currently hogging all your computing power.

Sometimes a process stalls, effectively freezing that action. By using the top command to find the Process ID (PID) of the offending process, you can halt the process. Simply use the kill command followed by the PID of the process that you want to stop. (The man help page for the kill command gives more options that may help terminate stubborn processes with prejudice.)

Figure 1.6. The top command displays all running processes.

Like top, another handy command for examining process info is ps (short for process). Most often, you'll want to append a few flags to the ps command to get the information that you desire. For example, try the following command:

ps –aux

The man page for ps explains what each flag means. (Read more about using the man command in the earlier section "Help is on the way!")

The command line gives you a number of ways to search for files on your hard drive. The two most commonly used commands are find and locate.

To use find, specify a starting point for the search followed by the name of the file or folder that you want to find. For example, to find the Fonts folder that belongs to your user, enter the command like this:

find ~/ -name "Fonts"

You should see at least one result of the find command.

/Users/markchambers//Library/Fonts

One great feature of the find command is that you can look for a file or folder in more than one location. Suppose you want to find a file named MyDocument that you know resides either in your Documents folder or on your Desktop. For this kind of search, use the find command like this:

find ~/Documents ~/Desktop -name "MyDocument"

In this example, you are telling the find command which folders it should search when looking for the file named MyDocument.

Nearly all UNIX commands can take on greater abilities by using a construct called the pipe. A pipe (|) is represented by that funny little vertical line that shows up when you press Shift+. The pipe routes data from one command to another one that follows — for example, many UNIX commands produce large amounts of information that can't all fit on one page. (You might have noticed this behavior if you've used the locate command.) Joining two commands or functions together with the pipe command is piping. To tame the screens full of text, pipe the find function to the less command. The less command provides data one page at a time.

find ~/ -name "Fonts" | less

When the results fill up one page, the data stops and waits for you to press any key (except the Q key) to continue. When you reach the end of the results, press Q to quit and return to a command-line prompt.

UNIX has many text-editing applications for use at the command line. Some of the more popular ones include pico, vi, and emacs. Each of these text editors has its pros and cons — and say thanks to the thorough folks at Apple, because all three are included with Snow Leopard! For my examples here, however, I use pico because it's simple to use and sufficient for our needs.

To create a text file by using pico, simply type pico at the command line. The result looks like Figure 1-7.

Figure 1.7. The pico program is a fullstrength text editor, right from the command line.

At the bottom of the screen is a menu of common commands. Above the menu is a large, empty space where you can enter text, much the same as in the word processors that you already know and love. (For those of us that remember the halcyon character-based days of DOS, think older versions of Word and WordPerfect ...or, if you're a real computing dinosaur as I am, consider the original WordStar.) Type some text in that area. Anything will do ...a letter to a friend, a grocery list, or your school homework.

When you're finished entering your desired text, save the document with the WriteOut command in the pico menu. Directly next to each command in the pico menu is a keyboard sequence used to perform that command. (Refer to the bottom of Figure 1-7.) The

After pressing the Control+O sequence, pico prompts you for a filename. Like most UNIX files, you're permitted to enter a simple filename here or a full path to a file. For this example, save the file to your Documents folder, naming it MyPicoDocument.

After you've completed and saved the document, pressing Control+X will transport you away from Planet Pico and back to the command line.

Because UNIX isn't a new phenomenon, it has many useful networking abilities built into it. In fact, UNIX was instrumental in creating much of what we now take for granted: e-mail, the Internet, and the World Wide Web. Thus, you'll be happy to know that you can communicate over networks with the Terminal in practically any manner that you can dream of ...and then some!

curl http://www.mlcbooks.com

curl -o ~/mlcbooks.html http://www.mlcbooks.com

curl -o ~/Desktop/README.curl ftp://ftp.sunet.se/pub/www/utilities/curl/README.curl

curl -T /Desktop/README.curl -u username:passwdftp://ftp.yoursitehere.com
/myfiles/README.curl

curl dict://dict.org/d:DVD