Mar 10, 2014 At the command-line level, most documentation comes in the form of man pages (short for manual). Man pages provide reference information for many shell commands, programs, and POSIX-level concepts. The manual page manpages describes the organization of manual, and the format and syntax of individual man pages.
The OS X Terminal is a very powerful tool for configuring and using a Mac, and can be used to script and program a number of aspects of the computer's operations; however, its text-based interface can be a bit of a cryptic environment to first-timers, especially when it comes to finding out what you can use it for.
There are thousands of Terminal commands available, but when you first launch it you might not have a clue where to look for them. Of course there are basic commands like 'ls' for listing directory contents or 'cd' for changing directory, but in addition there are text editors, string parsers, expression managers, and numerous other commands that, depending on the purpose, can make the Terminal a hidden but exceptionally powerful tool.
If you are just getting started with using the Terminal, you may find it useful to build your command vocabulary. There are many resources such as the BSD Unix command summary that will give you a quick overview of the common commands; another approach is to list all commands available to you and then look up the manual page of each individually to see what its purpose is and how it's used.
There are a number of ways to list all of the commands, but two quick ones are Tab completion and the 'compgen' command. For Tab completion, simply type something in Terminal and hit Tab once or twice (and if prompted, confirm that you want the options displayed) and the system will list all available commands based on the text you entered.
If you press the Tab key without having entered any text, then the Terminal will output all possible commands (after you confirm that you want it to do so). If you do this, it helps to make the Terminal window as large as possible. You can then press Enter to display more items that are off the page until you are dropped to the command prompt again, but then you can scroll up and down to review the commands that were listed.
The second option is to list the commands and aliases available to you using the 'compgen' built-in command. Simply type the following command, and you will be given the full alphabetical list of commands available to you in the system:
compgen -ca
You can also redirect the output to a text file on your desktop called 'commands.txt' to peruse later:
compgen -ca > ~/Desktop/commands.txt
Referring to this list of commands, you can then look each up using the Terminal commands 'man' for the full manual page or 'whatis' for a brief synopsis of what it does. For instance, unlike the command 'diskutil' it may be difficult to guess what the command 'xattr' does from its name, so you can quickly look this up by running the following:
whatis xattr
Note: If the whatis command is not working then run the command '/usr/libexec/makewhatis' in the Terminal.
You can find more information and specifics on how to use the command through its manual page. There are a number of approaches to viewing a manual page for a command, with four that may be most useful:
- The man command
The default way to view a manual page is to use the man command the way the whatis command is used above, which will bring up a formatted instruction manual for the command that you can navigate through with the arrow keys or the F and B keys (for forward and backward). For example, to view the manual page for the xattr command, you would run the following:man xattr
To quit the manual page, simply press the Q key. - The 'xman' command
If you have XQuartz installed or Apple's provided X11 windowing system for Unix (provided by Apple in OS X Lion and previous versions), then you can run the 'xman' command to open up a manual page browser that you can click through. This is a quick and convenient way to not only view the manuals, but also see the available commands. - The Web
A third resource is various Web sites that contain collections of man pages for commands. An easy approach is to simply do a Web search for 'man COMMAND;' however, this may bring up platform-specific manual pages that do not completely pertain to the command in your version of OS X. A more Mac-specific man page collection is Apple's OS X Manual Pages site. - Third-party man page utility
A final option is to use a third-party manual page tool, such as OnyX, which contains a full man page browser. Like the xman utility, this will give you a quick way to view available commands and study their manual pages. In addition, OnyX provides an option to save the manual pages as PDFs.
Mac Os Terminal Commands
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OS X's command line and I have never been what I'd call 'friendly'; rather, we have a mutual respect and understanding about not messing with each other. (Well, as much of a mutual respect as one can have between a human being and a code window.)
While the average person should never have any reason to visit Terminal, Apple's command line interface app actually does give you access to quite a few neat tricks and shortcuts... if you're willing to take a peek.
What is Terminal?
Apple's Terminal app is a direct interface to OS X's bash shell — part of its UNIX underpinnings. When you open it, Terminal presents you with a white text screen, logged in with your OS X user account by default.
Here's the important part: With a system administrator account and password, you have direct access to tweaking almost everything about your computer's software code; that means that while this little window provides great power, it comes with great responsibility. In short, be careful before using Terminal to execute commands, and make sure you understand what you're typing.
You can also use Terminal to securely connect to other machines, web servers, and even create your own scripts, but those are how-tos for another day. For now, we're going to focus on using Terminal to explore your own computer.
Basic Terminal commands you should know
Before we get started with the fun stuff, let's learn some basic Terminal terminology and commands. These form the framework for more complex interactions (aka, the fun stuff).
How to execute a Terminal command
You can type something in the Terminal window until you're blue in the face, but it won't execute until you press the Return key on your keyboard. At that point, it will either return an error if you've typed something incorrectly, or the command will execute.
Unless you're executing a command that requires the display of text in Terminal, you won't have any indicator that what you've done has been successful; you'll just get a new line with your user name on it once the command is finished processing.
When writing commands and paths in Terminal, almost everything is case sensitive: This means that you need to remember to properly capitalize 'Dock' when referring to the Dock, or OS X won't understand your command.
What's a path?
You can use Terminal to get direct access to your files without using the Finder. To do so, you build something called a path. Paths look similar in some ways to website sub-directories, and follow the structure of your folders.
Paths take two forms: absolute paths and relative paths. An absolute path starts at the root level of your hard drive, and is displayed as '/'. So if you wanted to make a path to your Applications folder, you would write '/Applications/'.
Relative paths are defined based on where you've already navigated to, and represented by './'. For instance, if you go to the '/Applications/' folder in Terminal, that's your current working directory (cwd). You can then get to your Utilities folder by typing './Utilities/' rather than '/Applications/Utilities'.
When you first launch Terminal, you're starting in the current working directory of /Users/myusername/ (also known as your User folder).
How to display and move between files in Terminal
To actually put all this path knowledge to use, you'll need the Terminal commands for displaying and changing files.
ls: The 'ls' command, by itself, displays the contents of the cwd. So if I were just to type 'ls' in Terminal, it would display the contents of my user directory:
You can optionally add an absolute or relative or path if you want to view a different directories. So, for example, if I wanted to view the Utilities folder inside Applications, I could type 'ls /Applications/Utilities/'. This won't change your current working directory, but it'll let you view other directories on your hard drive.
You can add options to view more information about that directory. The options for 'ls' include:
- -l, which lets you view the permissions of each file in the directory
- -R, which will not only show each folder in the directory, but all their files, as well
- -a, which will show any hidden files in the current directory
cd: Where the 'ls' command lets you view a directory, the 'cd' command will actually move to that directory (change your cwd). For instance, if after viewing the Utilities folder, you want to move to it, you'd type 'cd /Applications/Utilities/'.
pwd: Write this command by itself to help you remember the path of your current directory. When typed into terminal, it will print the full path of your cwd.
man: This command, followed by another Unix command, lets you read the Unix manual about the second command. This is super useful if you want to try a cool Terminal trick you found online, but aren't sure what those commands actually do.
For instance, typing 'man ls' will get you information on the 'ls' command, which lists directory contents.
How to modify files, folders, and preferences in Terminal
defaults: This command is often used in Terminal tips and tricks to tweak applications and system settings via their preference files. You can use it to do things like disable transparency in the menu bar, always show your scroll bars, change trackpad behavior, and much much more. You'll usually see this paired with either 'write' and a string, as with this:
The code above lets you save all your screenshots as JPGs instead of the system default PNG.
killall: If you execute a Terminal command that affects any system process or app, you're going to need to reboot the process to make it take effect. 'killall' followed by the process will do so. (This is also another way to force quit misbehaving apps or processes if your Force Quit menu isn't behaving.) Remember, this command and its target are case sensitive.
ln: OS X has long offered aliases, which let you create links to files, folders, and applications elsewhere in the system without having to duplicate them. Unfortunately, certain apps don't play well with aliases. With the link command 'ln -s', you can create a low-level, UNIX-based symbolic link which most system processes will recognize. Likely, you'll never have to make a symbolic link, but on the off-chance you want to perform a Terminal trick that requires them, this is how you do it.
The first path listed is your original file's path; the second path is where you'd like your symbolic link.
chflags: This commands lets you view and change the flags on a file or folder. For most people, the only flags you're going to care about are 'hidden' and 'nohidden', which hide and unhide documents, respectively.
sudo: If you spend any time online, you've probably heard of 'sudo' before. This is Unix's override command, and lets you execute any command as an administrator — provided, of course, that you have the requisite password and permissions. It probably goes without saying, but as a Terminal beginner, it's generally a good idea not to mess with commands like 'sudo' unless you are 100 percent sure what you're doing.
How to use Terminal for fun and whimsy
say: Feeling lonely? You can make your computer say anything you like with the 'say' command, and you can even record it in audio format to your desktop, if you so choose.
telnet towel.blinkenlights.nl: This isn't technically something local to your Mac, but it's my all-time favorite Terminal trick. Some kind soul on the internet made an all-ASCII version of Star Wars: A New Hope; run the following code, and you'll be treated to a full showing. If it doesn't make you smile just a little bit, you might be dead inside.