Work with Paths in UNIX Commands

Before you dive into UNIX commands, you should first know a few facts. 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>.

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/

As you’ve probably surmised, a folder and a directory are two different names for the same thing. Folder is the name with which most Mac users are familiar, and directory is a term that UNIX power users prefer.

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$

Of course, the Home directory is a special folder in that you can also navigate there by simply entering cd ~, but the main point here is that you can navigate directly to specific folders by using that folder’s path in conjunction with the cd command.

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.

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Source:http://www.dummies.com/how-to/content/work-with-paths-in-unix-commands.html