CS220 - Computer System II Lab 0

Deadline: 08/25/2016 by the end of lab

Introduction

In this lab, you will learn to:

Develop, compile, and execute a simple C program in command-line environment
Use make to control builds
Use tar to create archives
Use git to manage your projects and submit your work for grading.

Look for these icons!

	Meaning
💡	Tips and useful information
⚠️	Caution! This could cause you problems.
⛔	Danger! Don't do this!

Getting Started

All students should have card access to room G7 and login information (username and password) to lab machines. If not, please contact TA or Professor for assistance. You can use any machines in G7 to complete your lab work, programming assignment, and projects for this class. However, please be mindful of the lab schedule posted outside and avoid using the room when other classes are in session. If you decide to work from home, you can either try ssh from your terminal (if you have Mac or Linux system) or a GUI SSH client. To log into to this lab machine from a terminal, simply type this command:

ssh username@remote.cs.binghamton.edu

... where username is your CS LDAP account.

Writing Hello World

After loging in, open a terminal.

First, let's set up our git credentials. Enter the following two commands in the terminal:

git config --global user.name "Firstname Lastname"
git config --global user.email "email@binghamton.edu"

You should be at your home directory. In this directory, create a new directory for this class:

mkdir cs220

Change your working directory:

cd cs220

Then, clone this repository to get a copy of the source code onto your account. To do this, look at the Github landing page for your fork of this project. You should see a green button that says "Clone or download". Press it and choose "Clone with HTTPS" if you haven't already. You should see something like https://github.com/bucs220/F17L0.git. Copy that text then execute the following command in the terminal:

git clone URL

... where URL is the copied text ending in ".git".

We will explore git workflows in-depth later in this lab.

Text Editors

Remote has a variety of text editors available. If you prefer a graphical text editor, you can use gedit. If you are more comfortable with command line editors, you can choose vi, emacs, or nano.

💡 Useful resources:

Open your favorite text editor and write a simple Hello World program in C. Name your source code file ”hw.c”

#include <stdio .h>

int main() {
  printf (”Hello World!\n”) ; 
  return 0;
}

Compile your Hello World program:

gcc hw.c −o hw

This command invokes a C compiler, gcc, and produces an executable file called hw. Execute your hw program:

./hw

Make

Make is a build tool that automatically generates executable from multiple source code files. When you invoke make, it will search for a file named Makefile in current directory. This Makefile contains rules to build a program. A basic rule in Makefile has the following form:

target: dependencies
	command

⚠️ Note that command is indented using a tab character, not spaces!

💡 Also note that a target can have multiple dependencies (all on one line) and multiple commands (on separate lines, as does the clean target below).

Create a Makefile for your Hello World program. Here is a simple example:

all: hw 

hw: hw.c
	gcc hw.c −o hw

clean:
	rm −f hw
	rm *~ #*#

Make has the following form on the command line:

make [target]

If you do not provide a target, make will use the first target listed in the file, which in this case is all. Make will compile the program using the command we specify in Makefile. In this case, to compile Hello World program, type:

make hw

You can also provide multiple targets for make. For example:

make clean hw

This make command will delete your existing hw binary and compile a new one.

💡 To learn more about make and Makefile, here are some useful resources:

command	action
`tar -cvzf lab0.tar.gz hw.c Makefile`	Create an archive containing `hw.c` and `Makefile`
`tar -tvf lab0.tar.gz`	Display the contents of the archive
`tar -xvzf lab0.tar.gz .`	Extract the contents of the archive into the current directory

Git

⚠️ These commands all presume that your current working directory is within the directory tracked by git.

In this lab, we will use Github Classroom repositories. You have already forked this repository when you accepted the emailed link. That makes a copy of the repository, free for you to make changes. Then you cloned your forked repository to get a working copy onto this machine.

Now that we have made local changes to our working copy, let's commit those changes to the repository:

git commit -a -m "My first commit!"

The -a says that git should add all tracked files with changes to your commit, and the -m says the next string contains the commit message.

What about untracked files? Run the following commands:

echo $(whoami)@$(hostname):$(pwd) > information.txt
git status

You'll notice that git tells us that information.txt is an untracked file. That means it's not being tracked by the repository. Let's fix that by adding it.

git add information.txt
git commit -m "Added an informational file"

Once we've made the commits for a given coding session, we need to add those to the repository by performing a push:

git push

Now, let's say we don't want information.txt in the repository anymore. How can we remove it?

git rm information.txt
git commit -m "Removed an informational file"
git push

Lastly, the next time we begin a coding session, we will need to pull to get an updated working copy.

git pull

That's it! We've completed our work for this lab. Now to submit it.

💡 Useful git references:

Submission

⛔ Please read submission instructions carefully. Any deviations from specifications on future labs, assignments or projects will result in point deductions or incomplete grades.

Create a release of your repository:
1. Click "releases", next to the tag icon.
2. Click the "Create a new release" button.
3. Fill in the tag version (i.e. 1.0), the release title (i.e. "First submission!") and add any comments that the grader needs to know about your submission.
4. Click the "Publish release" button.
5. On the next page, you will see that your release has a 7-digit hexadecimal number. This is the hash of the release, uniquely identifying the state of the repository that was used to make the release. Copy that.
Log onto MyCourses.
1. Find this assignment.
2. Make a submission as you normally would for any other class. The difference is that instead of uploading an archive file or source code, all you should do is paste the 7-digit hash into the comments.

The MyCourses submission notifies the graders that your repository is ready to be graded. Your grade for the lab, assignment or project will be recorded on MyCourses. For labs, the TAs can grade your submission on the spot. Simply raise your hand to get our attention.

GSteinberg/cs220-f17-lab0-GSteinberg