The filesystem on Unix-based systems can be accessed not only through the point-and-click graphical user interfaces (GUIs) that we're all used to, but also by typing text commands. These commands are entered through an interface called the Terminal. On Mac OS X, Terminal can be found in Applications > Utilities. After opening Terminal, you can type commands at the command prompt (which usually ends with > or $).
To start navigating the filesystem, it helps to know where you are (i.e., your current working directory). You can print the absolute path to your current location using
pwd - print working directory.
After opening Terminal, use pwd to see the default working directory. To view the contents of this (or any) folder, you can use the list command
ls - list the contents of a directory.
To see more information about these contents you can add the -l flag (i.e., option) to the list command
ls -l - list directory contents in the long format.
More information about options for the list command can be found here. Adding the -a flag will display "hidden" files and folders
ls -a - list directory contents, including hidden files and folders
While these commands can indicate your location in the filesystem and the contents of that folder, you'll need to be able to change your location. This is accomplished with the change directory command
cd <PATH_TO_NEW_LOCATION> - change your working directory
Note that through these notes elements with angled branckets <...> should be replaced when executing commmands. For instance, if you are in a particular user's directory (e.g., /Users/UserName/) and you want to go to that user's desktop folder, you could use
cd Desktop
In general, any relative or absolute path can be provided as an argument to cd. Remember also the special symbols like .. and ~. These are valuable shortcuts when moving around. For instance, to move to the parent of your current working directory, you can use
cd ..
Similarly, to move up two parents in the hierarchy, you could use
cd ../..
No matter where you are in your filesystem, you can immediately return to your home directory with
cd ~
and you can immediately get to the root with
cd /
Practice Exercise
(1) Move to your home directory.
(2) List your home directory contents
(3) Move to a folder inside your home directory
(4) Verify your current working directory
(5) In one command, move to the parent of your home directory
(6) Verify your current working directory
One very powerful feature of working at the commandline is the ability to use wildcards. These are symbols that can match many other characters (or sets of characters) and allow you to list, view, or manipulate multiple files at once. The most general of these is *. This symbol can match any type or number of other characters. For instance, to list all of the files in a directory that end with .txt, you can use
ls *.txt - list all of the text files ending with .txt
You can also mix and match standard characters with wildcards for more sophisticated patterns. For instance, to find all the files that start with m and end with .txt, you can use
ls m*.txt - list all files starting with m and ending with .txt.
As you type in Terminal, it stores a record of the commands you've used recently. This feature can be very helpful if you need to reuse a command later. For instance, at a fresh command prompt, just press the up arrow key. You should now see the last command you used! If you keep pressing up, you can scroll back through your command history.
If you want to see this history, you can use the history command.
history - display your latest command history
This will display all of your most recent commands on numbered lines.
Another useful trick when working at the command line is tab completion. As you start to type a command or a filename, the system will try and guess what you want if you press tab. If it is unable to distinguish among the possibilities, nothing will happen when you press tab. But if you've typed enough for the system to fill in the rest, it will!
For instance, type each of the following and see if the system can guess that you want to execute the history command.
h + tab - Does it autocomplete the command?
hi + tab
his + tab
hist + tab
histo + tab
histor + tab