[SOLVED] Cse 3100 systems programming lab #0

After lab 0, you should be able to access your VM, use basic commands in a shell (e.g. to copy/remove/rename
files), edit text files like C source files, compile and run simple C code, and submit your work.
1 Setting Up Your VM
Before you can access your virtual machine, there is a short setup to complete.
1. Ensure you are connected to university Wi-Fi and that you have a mobile device for
2FA. If you are not connected to university Wi-Fi, you will need to use the UConn AnyConnect VPN
available here. (This applies to when you are using the virtual machine for the duration of the semester
to work on assignments. If you are not connected to university Wi-Fi, you need to be connected to the
VPN.)
2. Open a terminal on your local machine and SSH (Secure Shell Protocol; a way of connecting remotely to the terminal of another machine in a network.) into your VM at the address [NETID]-
vm.cse.uconn.edu/. If you are on Linux, you can run
ssh [NETID]@[NETID]-vm.cse.uconn.edu
to connect. If you are having issues with SSH or are unsure how to do so on Mac/Windows, ask your
TA.
3. Enter your NetId password when prompted. You will not be able to see what you are typing as it is
hidden to not reveal your password. Press enter when finished.
4. When prompted for 2FA, enter either 1 or 2 and press enter to select your preferred 2FA method.
5. You are (hopefully) now connected to your VM by SSH! Now, every command you type is run by your
VM and relayed back to you in the terminal you have open! To quit the connection, you can run the
command exit.
6. Run the command /opt/scripts/codefix.sh, which sets up your VSCode environment for browser
usage.
You should now have access to your VM in browser at the address [NETID]-vm.cse.uconn.edu! You can
just enter this into your browser of choice and begin working. Two very important things to remember for
the VM:
1
• BACK UP YOUR WORK! VMs are NOT backed up. Losing significant work to data
loss on the VM is not an excuse. If you are done working on a file in your VM, make
sure you download it to your local machine just in case.
• VMs undergo maintenance from 5:30AM to 7:30AM. There is a possibility that machines
are down during this time, so do not plan on having access during this block of time.
2 Shell
In the shell (most likely bash), try the following commands (and explore a bit!):
pwd Show the current directory (where you are).
ls List the files and directories in a directory.
ls -l The -l flag tells ls to show more details.
mkdir adir Create a directory. Try different names.
ls -l adir Lists the files in the directory ’adir’.
cd adir Move into the directory ’adir’.
ls -l .. List the files in the parent directory.
cd Go back to your home directory.
cd adir Go to ’adir’ again.
echo “hi!” Print ’hi!’ to the standard output (stdout).
echo “hi!” > file Save ’hi!’ to a new file called ’file’
cat file Print the contents of a file to stdout.
grep “hi” file Search the file for the string ’hi’.
less file View the file interactively (q to quit).
rm file Permanently deletes the file.
cat Read from standard input (stdin) and dump to stdout. Ctrl-D to exit.
history Show history of commands.
man ls Show the manual for the ’ls’ command.
man cat Show the manual for the ’cat’ command.
man scanf Show the manual for the ’scanf’ function.
exit Exit from the shell.
3 Text editors and your first C program!
To work on a project, you need to go to the corresponding directory in the virtual terminal. Normally
Coding Rooms goes to the correct directory when you start a virtual terminal. Under the project directory,
you can modify existing files and/or create new files (.c files, .h files, readme’s, make files, etc.).
You can use the web editor, or an editor in the virtual terminal, to edit text files, which include your C
source code. If you decide to learn an editor in the terminal, there are three primary options: vim, emacs,
and nano. It is highly recommended to learn one of them, in addition to the web editor.
Use your favorite editor to open lab0.c. If you use the editor in the Coding Rooms IDE, you can click
on the Files icon (top left) and you can use use the buttons. Otherwise, here are different ways to do it in a
terminal. The following three editors are available in many systems.
vi lab0.c
emacs lab0.c
nano lab0.c
2
Add the following C code in lab0.c. If you are using the editor in the Coding Rooms IDE, changes
should save automatically. Otherwise, remember to save the file after editing.
#include <stdio.h>
int main(void)
{
printf(“Hello, World!
”);
return 0;
}
This is your first C program! Before you can run it, you must compile it. You can do so by typing the
following command in shell/console, or by clicking the ‘Run’ button in the Coding Rooms IDE. Note that
you can use console/shell at the bottom of the Coding Rooms IDE. If you would like, you can also use the
tips in ?? to open a visual desktop, where you can open multiple terminal windows.
cc lab0.c
This will compile your C code in lab0.c and create an executable called a.out. If the process fails, read
the error messages, fix the error in your C file (using the text editor), and try again. If there is no error, you
will see a.out in your current directory.
You can optionally specify the name of the executable that is generated by the compiler.
cc -o lab0 lab0.c
To run your program, type
./lab0
4 Something new
Revise lab0.c. Use a while loop to calculate the sum of positive even integers below 200 and print the
result to the standard output. This is very similar to the sum example we have studied. Think about how
much you should increase the loop control variable to get to the next even number.
Your program should output the following text:
Hello, World!
9900
5 Submission
If you think your code works, you should submit it on gradescope. You can download the files you have
worked on in the file directory interface to the left of the IDE. There is a link to gradescope in the HuskyCT,
you should already be added to the course with your UConn email.
Please remember to submit your work before the deadline for each assignment and exam.
Enjoy!
3
Exit from an editor in terminal
There are many tutorials on nano, vi/vim, and emacs. Feel free to explore and share with other students.
In case you are stuck in an editor, here are the commands you can exit from the program.
nano
nano is very user friendly. You can see the help at the bottom of the screen.
nano a.txt Start nano to edit file a.txt
Ctrl-x Exit from nano. See the prompt at the bottom of the screen
There are many tutorials on the Internet, for example, here.
emacs
Commands in emacs are control characters or prefixed a set of characters.
emacs a.txt Start emacs to edit file a.txt
Ctrl-x Ctrl-s Save file
Ctrl-x Ctrl-c Exit from emacs
Here and here are examples of cheat sheets and tutorials on emacs.
vi/vim
vi has three modes. Normally, you are in the normal mode when vi just starts. Press i to enter the insert
mode, where you can insert/type text. Press Esc to exit from the insert mode and get back to the normal
mode. If you get lost, press Esc many times to get back to the normal mode.
vi a.txt Start vi/vim to edit file a.txt
:wq Save the file and then exit from vi. Work in the normal mode
:q! Exit from vi without saving file. Work in the normal mode
Here is an example cheat sheet.