Written by Chris Gregg, Julie Zelenski and others, with modifications by Nick Troccoli and Lisa Yan
This guide walks you through all the steps to start working on your first program for CS107. You will complete all your programs for CS107 on the
myth cluster, which is a set of computers in Gates B08 running Linux (Ubuntu 14) and have various open source tools installed (
gdb, etc.) that we will use. These systems are networked and use a common set of accounts (your SUNet id/password) and have a shared AFS filesystem. There are 30 or so machines in the cluster, individually named
myth2, and so on. No matter which myth you log into, you'll have access to the same installed software, your home directory, and all your files.
Step 1: Install SSH Program
The first step is to set up your own computer to log in to
myth remotely. Logging in through a command called
ssh will allow you to work on the myth computers in a way that is indistinguishable from being physically in the Gates B08 room. While some version of
ssh is available on all kinds of computers, the exact details of this step will be different depending on what kind of computer you have.
If you have successfully followed these instructions and logged in to myth, you should see something like this:
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= myth57.stanford.edu Ubuntu 20.04 (5.4.0-70-generic) 8 x Intel(R) Core(TM) i7-7700K CPU @ 4.20GHz, 31.24 GiB RAM, 31.87 GiB swap =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= -> For help with your SUNetID, AFS, or class dirs call 725-HELP, or visit http://helpsu.stanford.edu -> For problems with hardware or local/OS software, visit http://support.cs.stanford.edu -> With the exception of certain course related mail, the myths cannot be used to send or receive email -> The myths are not for CPU-intensive workloads. For alternative computers see http://farmshare.stanford.edu -> The new myths are: myth51 - 66 SUNET@myth57:~$
The "myth57" part may name a different myth (myth1 or myth12, etc). Remember that Gates B08 contains many myth machines. When you ssh to "myth.stanford.edu" as a generic name, you are randomly assigned to one of the myths that is currently most idle (fewest other people trying to use it). This log in greeting message is simply telling you which one you were assigned. You may also ssh to a specific myth by using that myth's name (e.g.,
ssh email@example.com), but you usually won't need to do this.
When you log into the myth computers, you are automatically put in your home directory (
~), your personal file space on myth. You have access to read, write, and delete files inside your home directory, but you can't read another person's directory unless you have permission.
When you're working via
ssh, remember to save early and often. If you get disconnected from
ssh while you are working, you will potentially lose any work up to the last time you saved.
When you're ready to log out, you can just close the window, or enter "logout" to log out.
As you're working and entering commands, if your command-line is getting too cluttered, you can use the
clear command to clear the currently displayed output. To do a deeper clear, you can use the
reset command, which will fully re-initialize the display. The
reset command is useful if your input-output somehow get mismatched, but
clear will be faster and will work for most use cases.
Step 2: Configure Tools
We will use various tools already installed on the myth machines to work on programs. First, we need to configure them with the correct settings. You only need to do this once.
First, we need to set up a text editor to use for the quarter. We officially support the
emacs editor this quarter - it is preinstalled on the myth machines and because you are always editing your files on the myth machines via ssh with this editor, it means there is less risk of you losing your work. While you are not required to use it, it is the only editor we can provide support for in CS107. Learning a Unix-based editor is an essential skill!
Emacs is a text editor for editing files on the myth machines. First, we'll set up Emacs to do things like use mouse controls, display line numbers, standardize indentation, etc. To do this, execute the following command immediately after logging into
wget https://cs107.stanford.edu/resources/sample_emacs -O ~/.emacs
Emacs looks for a special
.emacs file on your system to know what preferences you would like, and this command downloads our pre-made one and puts it on your system. If you don't do this, you won't be able to use some of the shortcuts and commands highlighted in lecture and the guides. If the command above worked correctly, you should see something like the following outputted to your terminal:
--2020-09-14 14:08:35-- https://cs107.stanford.edu/resources/sample_emacs Resolving cs107.stanford.edu (cs107.stanford.edu)... 184.108.40.206 Connecting to cs107.stanford.edu (cs107.stanford.edu)|220.127.116.11|:443... connected. ... MORE TEXT HERE... Saving to: ‘/afs/ir/users/t/r/troccoli/.emacs’ /afs/ir/users/t/r/t 100%[===================>] 1.45K --.-KB/s in 0s 2020-09-14 14:08:35 (61.3 MB/s) - ‘/afs/ir/users/t/r/troccoli/.emacs’ saved [1489/1489]
GDB is the debugger we'll use in CS107 to debug programs. First, we'll configure it to use the CS107 default preferences; this sets up the debugger to know things like that our work will be in 64-bit systems. To do this, execute the following command immediately after logging into
wget https://cs107.stanford.edu/resources/sample_gdbinit -O ~/.gdbinit
gdb looks for a special
.gdbinit file on your system to know what preferences you would like, and this command downloads our pre-made
.gdbinit file and puts it on your system. If you don't do this, some behavior may not match guides and examples in CS107.
Step 3: Your First C Program
Each student has their own personal file space on myth. Before working on CS107 programs, it's a good idea to make a folder for your work this quarter, so you know where you can find it. Try making a folder called "CS107" like this:
Then go into that folder like this:
Now, let's try making a copy of the lecture 1 code, so we can try out the different tools. Make a copy like this:
cp -r /afs/ir/class/cs107/lecture-code/lect1 lect1
This makes a copy of the code and puts it in a folder where you currently are called
lect01. Go into that folder:
Let's open the
args.c program in a text editor.
Enter the following:
When you get the program open, pull up the
emacs guide and try out some of the commands to get the hang of your way around.
When you're done, put the code back into its original state. Then try quitting the editor.
Now, let's try running the program. When you are in a CS107 project folder that we have provided, type in the
make command to compile all the programs. The
make command looks in the current directory for a file called
Makefile with instructions on how to compile things. We always provide one for you. If all goes well, you should see something like this:
myth$ make gcc -g3 -O0 -std=gnu99 -Wall $warnflags args.c -o args gcc -g3 -O0 -std=gnu99 -Wall $warnflags bool_fun.c -o bool_fun myth64:~/CS107/lect1$
Now, let's run our program. We can run a program in the current directory by entering its name preceded by
And there you have it! You should see something like this:
myth$ ./args This program received 1 argument(s) Argument 0: ./args
Try adding more arguments - you can pass in arguments to a program in the terminal when you run it. These arguments are accessible as string parameters to your program's
myth$ ./args hello cs107! This program received 3 argument(s) Argument 0: ./args Argument 1: hello Argument 2: cs107!
Congratulations - you've just edited and run your own C program. Try going back to
args.c to edit the code, compile it again, and run it to see the changes. Remember to always re-compile using make when you make changes! If you don't run
make, the changes won't be compiled into your program.