Configuring code-camper accounts

Topics/tags: Code camps, the joy of code, technical

Unlike the Data Science for Social Good camp, which had the students do most of their work in the cloud [1], the Language and Code camp has students working directly in MathLAN. They are creating HTML and CSS files and writing programs in Racket. That means that we have a lot of configuration to do. Let’s see …

• We need to set up their HTML directory [2] and set the permissions appropriately [3].
• We should give them starter code for the HTML activities so that they can see some Web page in their home directory. That starter code belongs in their public_html directory.
• Most of the activities with Racket involve try this code, then make these changes [4]. We should give them the starter code for a variety of Racket programs.
• We are relying on a bunch of Racket libraries that need to be installed. I’d prefer not to have the students install them.
• The first time you run DrRacket, you need to tell it what default language to use [5]. Rather than making the students do the steps, we should just give them an appropriate configuration file.

The starter code belongs in Git repositories. That way, we can easily update if we make changes [6]. I’m okay continuing to use GitHub [7] for those repos. You can find the current starter HTML code at https://github.com/grinnell-cs/lac-public-html. You can find the current starter Racket code at https://github.com/grinnell-cs/lac-examples.

We can use raco pkg install to set up the Racket packages. At first, I was just using something like the following.

raco pkg install sxml

However, I don’t really want to re-issue that command if a package is already installed [8,9]. I know that raco pkg show will give me the list of all the installed packages. Let’s see what I can do.

rackages=`raco pkg show`;
function ri() {
  if `echo $rackages | grep -q "\b$1\b"`; then
  else
    raco pkg install $1
  fi
}

That’s not perfect, but it will suffice.

What’s left? The Racket configuration file. I can just copy that. Let’s see what my script looks like.

#!/bin/bash
# lac-camp
#   Set up a camper's account for the Language and Code camp.

# Set up the public HTML directory and associated permissions
if [ ! -d ~/public_html ]; then
  git clone https://github.com/grinnell-cs/lac-public-html.git ~/public_html
fi
chmod a+x ~
chmod a+rx ~/public_html
pushd ~/public_html
git pull
popd

# Set up the sample code directory
if [ ! -d ~/Desktop/lac ]; then
  git clone https://github.com/grinnell-cs/lac-examples.git ~/Desktop/lac
fi
pushd ~/Desktop/lac
git pull
popd

# Add the Racket packages
rackages=`raco pkg show`;
function ri() {
  if `echo $rackages | grep -q "\b$1\b"`; then
    :
  else
    raco pkg install $1
  fi
}
ri mcfly
ri overeasy
ri sxml
ri html-parsing
ri html-writing
if `echo $rackages | grep -q "\blac-camp\b"`; then
  :
else
  raco pkg install https://github.com/grinnell-cs/lac-camp.git
fi
raco pkg update https://github.com/grinnell-cs/lac-camp.git

# Add Racket configuration file if it does not exist
if [ ! -d ~/.racket ]; then
  mkdir ~/.racket
fi
if [ ! -f ~/.racket/racket-prefs.rktd ]; then
  cp ~rebelsky/share/initial-racket-prefs.rktd ~/.racket
fi

It took me a little bit to figure out the syntax for having no consequent for a conditional in bash [10]. Other than that, this was relatively straightforward. It seems to work well for the purposes for which I designed it. And, now that I’ve written it, a simple for loop lets me set up or update every camper’s account [11].

for user in $campers
do
  echo "----------------------------------------------------------------"
  echo "Setting up $user"
  ssh $user@`hostname` ~rebelsky/bin/lac-camp
  echo ""
done

There are times in which writing shell scripts slows me down. In this case, writing a shell script seems to have been a real win. I expect to use something similar the next time I have to get my CSC 151 students set up at the beginning of the semester. In that case, I won’t know their passwords, so I’ll have them run it themselves.

I’m glad that I have the skills to write scripts like these. Of course, I have the skills, in part, because I teach CS. If I didn’t teach CS, I probably wouldn’t need to write scripts like these [12].

Postscript: Grammarly tells me that this piece has a shorter-than-average word length. I expect that the code is having a negative effect on word length.

[1] Or, more precisely, on a Jupyter server.

[2] We’re running Apache with a fairly standard configuration. That means that Web pages are served from /home/USER/public_html.

[3] The home directory needs a+x. The HTML directory probably needs a+rx although one could argue that we don’t really need the r.

[4] At least most of the activities should take the approach of try this then make changes. Discussions with my research students suggest that I have not been clear enough in that message.

[5] I’m not thrilled with that design. But it’s not in my control.

[6] I don’t know how well that will work once the students start making their own changes. We shall see.

[7] I know that many people have moved away from GitHub because of the acquisition by Microsoft. I’m still comfortable with it. Perhaps someday I’ll switch to GitLab or to my own server.

[8] It’s not harmful; Racket just issues a note rather than re-installing. But I’d prefer not to have to read all of those notes.

[9] There goes my attempt to keep the shell script simple.

[10] The syntax of bash is weird. I still thought it was easier to have no consequent then to try to negate the test.

[11] Well, there is a little matter of passwords. But we had all of the camper passwords when we set up their accounts.

[12] That may not be true. There are many instances in which it’s useful to configure an account for a new user.

Version 1.0 of 2018-07-23.