Lab 1: Thoth, SSH, and C Solution

What is thoth?
thoth is a computer in the CS building. It’s hooked up to Pitt’s network, but the CS department manages it and puts software on it useful for this and other courses.

By logging into thoth remotely, you don’t have to worry about setting up a C compiler on your own computer.

ssh is a way of running commands on a remote machine. It’s like your command line, but the console is connected across the internet instead of to your own computer.

Later projects will also use features only available on thoth. So please don’t try to compile your projects on your local machine.


1. Getting connected and set up
Nothing will show up when you type your password. That’s normal.

When you log in, don’t worry about the “unauthorized access” message. You are supposed to be logging in. You’re authorized ;)

Windows users
You need to get an ssh client, like PuTTY (use the 64-bit installer). Run it, and use thoth.cs.pitt.edu as the address.

Say “Yes” to the certificate, give your username (lowercase) and password, and you’re in!

Mac users
Open up Terminal (⌘+Space, type “terminal”, hit enter). Then run:

$ ssh yourusername@thoth.cs.pitt.edu
Say “Yes” to the certificate, give your username (lowercase) and password, and you’re in!

If you can’t log in, please ask the TA for help. If you are sure you’re putting in your username in lowercase, and the right password, please email me and CC Dr. Khattab (skhattab@cs.pitt.edu). He’s the thoth administrator.


2. Common UNIX commands
Here’s a quick reference guide to refer back to.

pwd – display the current directory
cd dirname – change current directory to dirname

cd .. moves up one directory
cd ~ goes to your home directory
cd - toggles back and forth between the last two directories you were in
ls – list all files/folders in current directory

ls dirname will list files/folders in the directory dirname
mv source
dest – move or rename a file

source is the file you want to move/rename
dest is the new place/name
cp source
dest - copy a file from source to dest
mkdir name - make a new directory named name
touch
filename - make an empty file named filename
cat filename - display contents of text file filename
less
filename - view contents of text file filename - good for longer files

press q to exit!
rm filename - delete (“remove”) filename
rmdir dirname - delete an EMPTY directory named dirname
Where are we?
When you log in, you are placed in your home directory.

Try using pwd; it’ll show you the full path of your home directory.

Your home directory can be referred to as ~ in many commands as a typing shortcut.
Try using ls. It will list the files and directories.

Your private directory is what you want to do your work in. No one else can see it.
Do cd
private and you’ll move into that directory.

pwd again, and you’ll see that your directory changed.
You can use cd
.. to move up one directory.
You can use cd ~ to go to your home directory.

3. Setting up your ~/.bash_profile a little bit
bash is what you’re using right now - the thing you type commands into. .bash_profile is the configuration file for bash.

Do cd ~.

This goes back to your home directory.
Do chmod
u+rw .bash_profile
Now let’s edit it: nano
.bash_profile

nano is a very simplistic text editor that runs inside the terminal. The controls are at the bottom of the screen - something like ^X means press Ctrl+X. (Mac users, use the actual control key.)
Scroll down to the bottom of the file. There, you’ll see:

# Define your own private shell functions and other commands here
Use the arrow keys to put your cursor after that line. Now, copy and paste this exactly:

In putty, you can right click and paste
In Terminal on a mac, ⌘V will paste
if [ "$HOSTNAME" = "thoth.cs.pitt.edu" ]; then source /opt/set_specific_profile.sh; fi
If you want a nice-looking terminal prompt like I have, find the line that starts with export PS1, and replace it with this:

export PS1="[\[\033[1;32m\]\h\[\033[0m\] \[\033[1;34m\]\w\[\033[0m\]]: ";
Now hit Ctrl+O and hit enter to save. Then hit Ctrl+X to exit.
Do source
.bash_profile
Try doing man open. If you see this, yay! Hit q to exit.
If you see No manual entry for open then you messed up somewhere. Ask for help!


4. Making a “hello world” program
Organization is good. Don’t just do all your work in private. Make a directory for your 449 work!

Make sure you are in your private directory. Then do mkdir cs449.
Do ls, and you should now see cs449 listed. cd into cs449.
Now make a lab1 directory inside your cs449 directory, and cd into that.
Let’s make a C file. Do nano
lab1.c. This will create a new file and open it in nano.
Now type the following into the editor.

// Your Name (username) #include <stdio.h int main() { printf("Hello World!\n"); return 0; }
Save the file and exit nano.
Now, compile it like so:

gcc --std=c99 -Wall -Werror -o lab1 lab1.c
If you did it right, it should print nothing. With UNIX, “no news is good news.” Successful commands will usually be quiet. But if you ls, you should now see a new file, lab1. This is your executable!
Type ./lab1 to run your program. It should say “Hello, World!”

5. Archives and Submission
Your labs and projects will be submitted by copying (cp) files to a special directory.

Please follow these instructions for this and every lab/project you do. Bookmark this page!

Make sure your name and username are in a comment at the top of your .c file.
cd into your ~/private/cs449 directory.
Make a copy of the lab1 directory like so: cp -r lab1/ lab1_copy/

Making a copy reduces the chances of you losing all your work.
Make a tar archive. tar lets you bundle several files together.

This is the step everyone messes up and loses their work on. Please be careful.

Do this, using your username, not abc123.

$ tar cvf abc123_lab1.tar lab1/
Check that the tar archive has the right files.

Do tar tvf abc123_lab1.tar. It should look something like…

$ tar tvf abc123_lab1.tar drwxr-xr-x abc123/UNKNOWN1 0 2018-01-19 01:06 lab1/ -rw-r--r-- abc123/UNKNOWN1 78 2018-01-19 00:54 lab1/lab1.c -rwxr-xr-x abc123/UNKNOWN1 6424 2018-01-19 01:06 lab1/lab1
gzip the tar file to compress it. It’s as easy as:

$ gzip abc123_lab1.tar
Now it should have transformed into abc123_lab1.tar.gz.
Finally, copy it to the submission directory.

$ cp abc123_lab1.tar.gz ~jfb42/submit/449
It will say nothing if it worked correctly. No news is good news! But if you’re unsure, you can double-check that you submitted it properly like so:

$ ls ~jfb42/submit/449/abc123_lab1.tar.gz
and done correctly, it’ll show your filename:

/afs/pitt.edu/home/j/f/jfb42/submit/449/abc123_lab1.tar.gz
If you messed up and need to submit again, then fix your mistake, repeat these steps, but rename your tar file to abc123_lab1_2.tar.gz before copying it to the submission directory.

If you mess up again, repeat, name it abc123_lab1_3.tar.gz, copy.

If you mess up again, repeat, name it abc123_lab1_4.tar.gz, copy.

If you mess up again, repeat, name it abc123_lab1_5.tar.gz, copy.

If you…. ok I think you get the idea.

© 2016-2019 Jarrett Billingsley