Navigating Files and Directories

The part of the operating system responsible for managing files and directories is called the file system. It organizes our data into files, which hold information, and directories (also called ‘folders’), which hold files or other directories.

First, let’s find out where we are by running a command called pwd (which stands for ‘print working directory’). Directories are like places — at any time while we are using the shell, we are in exactly one place called our current working directory. Commands mostly read and write files in the current working directory, i.e. ‘here’, so knowing where you are before running a command is important. pwd shows you where you are:

Terminal

$ pwd

/home/student

Here, the computer’s response is /home/student, which is our home directory.

File system

To understand what a home directory is, let’s have a look at how the file system as a whole is organized. For the sake of this example, we’ll be illustrating the filesystem in a simplified view.

At the top is the root directory that holds everything else. We refer to it using a slash character, /, on its own; this character is the leading slash in /home/student.

Inside that directory are several other directories: bin (which is where some built-in programs are stored), data (for miscellaneous data files), home (where users’ personal directories are located), tmp (for temporary files that don’t need to be stored long-term), and so on.

We know that our current working directory /home/student is stored inside /home because /home is the first part of its name. Similarly, we know that /home is stored inside the root directory / because its name begins with /.

Typically, when you open a new command prompt, you will be in your home directory to start.

Absolute and Relative Paths

Whenever we refer to either a file or directory on the command line, we are in fact referring to a path. ie. a path is a means to get to a particular file or directory on the system.

There are 2 types of paths we can use, absolute and relative. Whenever we refer to a file or directory, we can, in fact, use either type of path (either way, the system will still be directed to the same location).

• Absolute paths specify a location (file or directory) in relation to the root directory. You can identify them easily as they always begin with a forward slash ( / )
• Relative paths specify a location (file or directory) in relation to where we currently are in the system. They will not begin with a slash.

To demonstrate, we can use command ls to look, what we have in DSIB01demo folder. We know, that Desktop is in our home directory, so we use path /home/student/DSIB01demo as parameter for ls command.

Terminal

$ ls /home/student/DSIB01demo

demo files LICENSE playground README.md scripts

Since we are already located in our home directory (as we verified by running pwd command), we can also reference path relatively from our current location and write just DSIB01demo.

Terminal

$ ls DSIB01demo

demo files LICENSE playground README.md scripts

More on Paths

You’ll find that a lot of stuff in Linux can be achieved in several different ways. Paths are no different. Here are some more building blocks you may use to help build your paths.

• ~ (tilde) - This is a shortcut for your home directory. eg, if your home directory is /home/student then you could refer to the directory Desktop with the path /home/student/Desktop or ~/Desktop
• . (dot) - This is a reference to your current directory. eg in the example above we referred to Desktop with a relative path. It could also be written as ./Desktop (Normally this extra bit is not required but in later sections we will see where it comes in handy).
• .. (dotdot)- This is a reference to the parent directory. You can use this several times in a path to keep going up the hierarchy. eg if you were in the path /home/student you could run the command ls ../../ and this would do a listing of the root directory.

So now you are probably starting to see that we can refer to a location in a variety of different ways. Some of you may be asking the question, which one should I use? The answer is that you can use any method you like to refer to a location. Whenever you refer to a file or directory on the command line you are actually referring to a path and your path can be constructed using any of these elements. The best approach is whichever is the most convenient for you.

Moving around

In order to move around in the system we use a command called cd which stands for change directory. The command cd may be run without a location and then it will always take you back to your home directory. But usually it will be run with a single command line argument which is the location we would like to change into. The location is specified as a path and as such may be specified as either an absolute or relative path and using any of the path building blocks mentioned above.

Result of cd command is that our current working directory will change.

Terminal

$ pwd

/home/student

$ cd ../

$ pwd

/home

Now let’s try going back to home directory.

Terminal

$ cd

$ pwd

/home/student

cd without an argument will return you to your home directory, which is great if you’ve gotten lost in your own filesystem.

Move around a bit.

Terminal

$ pwd

/home/student

$ cd DSIB01demo

$ ls

demo files LICENSE playground README.md scripts

$ cd /

$ pwd

/

$ ls

bin dev lib libx32 mnt root snap ...

$ cd ~/Documents

$ pwd

/home/student/Documents

$ cd ../../

$ pwd

/home

$ cd

$ pwd

/home/student

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