The purpose of this lab is to teach you some basic commands in the DOS operating system for those who are using a Windows machine. If you are using a Mac, read the Unix Lab instead.
You are probably already familiar with interacting with files and folders on your through the "File Explorer" program. File Explorer is a GUI (Graphical User Interface) which allows you to navigate through your file system and create new folders and documents, and organize them in ways that make sense to you. Sometimes in programming however, you will need to use your file system in a different way. For this, on Windows, you will use a program called "Command Prompt". The Command Prompt (formerly called a DOS Command Prompt) is known as a CLI (Command Line Interface). That means in addition to accessing your file system, you can also use the Command Prompt to run Python programs directly, among many other programming tasks.
You will find these basic commands useful as you try to run a Python program through a command line interface or to browse through the file system on your computer. Sometimes, you may have to deal with some of the internals of the Windows operating system in which case you may have to use some of the DOS commands.
Also note that the file system on your computer is structured in a hierarchical way. That means that files and folders are nested inside of other folders. There is some specific terminology we will use when dealing with hierarchical structures like this: directory (also called folder), parent directory, sub-directory, and file. When one directory contains another directory, the containing one is called the "parent directory", and the contained one is called the "sub-directory."
Open
the Command Prompt window on Windows 10 by going to:
You should see a mostly-blank window open that shows your user directory followed by the > symbol. This is called the command prompt, and you will often read or hear the phrase "enter this text at the prompt." That means type that text after the >.
An important thing to note is that in the Command Prompt you can use "tab-complete" to automatically finish the name of a file or directory so you don't have to type the whole thing. This will save you a tremendous amount of time and avoid typing mistakes. To tab-complete, begin typing the name of the file or directory and then hit the Tab key. If the Command Prompt is able to map what you've typed to a unique location, it will complete the name for you. If the Command Prompt finds multiple files or folders with a similar name, it will choose the first one and you can continue hitting the Tab key to cycle through all the options.
If at any point you want more information about a particular command you have entered, you can type
help
followed by the name of the
command you want information on. This command will display the instruction
manual for that command, including a description of what it does and all the
extra options you can add to change what the command does.
Enter the following at the command prompt:
help dir
In this case, it will tell you about the dir command, which prints the files and folders from where you currently are in the file system.
In the following exercises, you will try moving around various directories and creating and modifying files on your computer. As you follow the steps, try to find the same directories and files using the File Explorer program (not Internet Explorer) at the same time so you can see the effects of the commands you are entering.
1. Navigate to your Desktop within Command Prompt
cd Desktop
The cd command stands for change
directory, and it moves you in the Command Prompt to the directory you
entered after cd.
2. Create a new directory
mkdir NewDirectory
mkdir stands for make
directory, and it creates a new directory (or folder) named whatever you
type after mkdir.
3. List all of the files and directories in your current location
dir
dir stands for directory.
dir prints out additional
information such as the file size and time each file was last edited.
4. Move to the NewDirectory you just created
cd NewDirectory
Remember what cd means? This time you are
moving down a level in the file hierarchy.
5. Open the current directory in File Explorer
start .
By entering the . after the start command, you
are asking to open the File Explorer in the current directory.
6. Create a new file with File Explorer
All the changes you make in File Explorer and the Command Prompt are reflected on your actual file system. You can see this by using File Explorer to create a new file (right-click -> new -> Text Document), which you can then name "HelloDOS.txt". Next open the file and enter in your name and major in the file and save it. Now we will go see this new file by going back to the Command Prompt.
7. View the contents of HelloDOS.txt
more < HelloDOS.txt
The more command shows you the
contents of the file page by page.
8. Rename the new file you just created
rename HelloDOS.txt GoodbyeDOS.txt
This will rename the
HelloDos.txt file to the new name GoodbyeDOS.txt. If you instead wanted to make
a copy, you could instead type:
copy
HelloDOS.txt anotherGoodbyeDOS.txt.
9. Delete the file you just renamed
del /P GoodbyeDOS.txt
Here you use the /P option with del so that you get a
confirmation prompt before deleting the file, because once a file has been
deleted, it is gone forever! If you are sure you want to delete something, you
can omit the /P
option and just enter del <filename>, but be careful with that command!
10. Navigate back out of NewDirectory, back to your Desktop
cd ..
A single . indicates the
directory you are in. If you were to type cd . nothing would happen! But when you use two dots, that means
go to the parent directory of wherever you are. It moves you one level
up the hierarchy.
11. View a list of all the commands you just typed
doskey /History
This will will show you all
of the commands you have entered into the Command Prompt so far.
12. View the IP properties of a computer
ipconfig
This
command will show you the IP address, subnet mask and default gateway of each
network adapter.
13. See the group of users
net user
This
command will show you the network users of a computer.
14. See the computer's name
hostname
This
command will display the computer's network name.
15. Find round trip time to transmit and receive data to and from a server
ping <IP address> e.g. ping 172.217.175.100ping <site name> e.g. ping www.google.com
The
ping command sends packets of data to a specific IP address on a network, and
then lets you know how long it took to transmit that data and get a response.
16. Trace network route to a server
tracert <IP address> e.g. tracert 172.217.175.100tracert <site name> e.g. tracert www.google.com
Displays
jump from one network device to another when connecting to the IP X.X.X.X or
some site.
17. Display all active ports on a computer.
netstat
Displays
all active ports on a computer.
18. Display all active and inactive ports on a computer.
Netstat -a
Displays
all active and inactive ports on a computer.
19. Query the DNS name of an IP address.
nslookup <IP address> e.g. nslookup 172.217.175.100
This
command queries a DNS name of a computer represented by IP address.
And with that, you're done with the lab! Make sure you speak to your TA or instructor to get their sign off that you have completed the exercises, and don't forget to create a file named outputs.txt and copy and paste all of the input and output you just generated in Terminal there, save it, and upload it to Blackboard.
This only covered some basics of the DOS Command Prompt, so if you're interested in learning more there is a lot more information available online.