Creating and Changing Folders

On a Windows or Mac desktop, our present location determines what files and folders we can access. I can “see” my present location visually with the help of the graphic interface - I could be looking at my Desktop, or the contents of a folder, for example. In a Linux command-line interface, we lack the same visual queues to tell us what our location is. Instead, we use a command - pwd (print working directory) - to tell us our present location. Try executing this command on Lonestar6:

$ pwd
/home1/03439/wallen

This home location on the Linux filesystem is unique for each user, and it is roughly analogous to C:\Users\username on Windows, or /Users/username on Mac.

To see what files and folders are available at this location, use the ls (list) command:

$ ls

I have no files or folders in my home directory yet, so I do not get a response. We can create some folders using the mkdir (make directory) command. The words ‘folder’ and ‘directory’ are interchangeable:

$ mkdir folder1
$ mkdir folder2
$ mkdir folder3

$ ls
folder1 folder2 folder3

Now we have some folders to work with. To “open” a folder, navigate into that folder using the cd (change directory) command. This process is analogous to double-clicking a folder on Windows or Mac:

$ pwd
/home/03439/wallen/
$ cd folder1
$ pwd
/home1/03439/wallen/folder1

Now that we are inside folder1, make a few sub-folders:

$ mkdir subfolderA
$ mkdir subfolderB
$ mkdir subfolderC
$ ls
subfolderA subfolderB subfolderC

Use cd to Navigate into subfolderA, then use ls to list the contents. What do you expect to see?

$ cd subfolderA
$ pwd
/home/03439/wallen/folder1/subfolderA
$ ls

There is nothing there because we have not made anything yet. Next, we will navigate back to the home directory. So far we have seen how to navigate “down” into folders, but how do we navigate back “up” to the parent folder? There are different ways to do it. For example, we could specify the complete path of where we want to go:

$ pwd
/home1/03439/wallen/folder1/subfolderA
$ cd /home1/03439/wallen/folder1
$ pwd
/home1/03439/wallen/folder1/

Or, we could use a shortcut, .., which refers to the parent folder - one level higher than the present location:

$ pwd
/home1/03439/wallen/folder1
$ cd ..
$ pwd
/home1/03439/wallen

We are back in our home directory. Finally, use the rmdir (remove directory) command to remove folders. This will not work on folders that have any contents (more on this later):

$ mkdir junkfolder
$ ls
folder1 folder2 folder3 junkfolder
$ rmdir junkfolder
$ ls
folder1 folder2 folder3

A bonus command available on some Linux operating systems is called tree. The tree command displays files and folders in a hierarchical view. Use another Linux shortcut, ., to indicate that you want to list files and folders in your present location.

$ tree .
.
|-- folder1
|   |-- subfolderA
|   |-- subfolderB
|   `-- subfolderC
|-- folder2
`-- folder3

Before we move on, let’s remove the directories we have made, using rm -r to remove our parent folder folder1 and its subfolders. The -r command line option recursively removes subfolders and files located “down” the parent directory. -r is required for non-empty folders.

$ rm -r folder1
$ ls
folder2 folder3

Which command should we use to remove folder2 and folder3?

$ rmdir folder2
$ rmdir folder3
$ ls

Why could we use rmdir on folder2 and folder3, but not on folder1?

Review of Topics Covered

Command	Effect
pwd	print working directory
ls	list files and directories
ls -l	list files in column format
mkdir dir_name/	make a new directory
cd dir_name/	navigate into a directory
rmdir dir_name/	remove an empty directory
rm -r dir_name/	remove a directory and its contents
tree	list files and directories hierarchically
. or ./	refers to the present location
.. or ../	refers to the parent directory