From: George Francis
Date: 7/2/2006 8:56 PM
If you're impatient, here is a "dry recipe", else wait for a moment when I can show you directly on a pooter.
This email also contains a relevant lesson on unix (though with the usual transmogrifications, it applies to Windows boxen too.) A webserver (the thing you address when you write http) runs on a computer as a daemon, called httpd. When a message like http://new.math.uiuc.edu/im2006/watt/ arrives on new.math.uiuc.edu the httpd looks into the directory with a much longer path, something like /var/www/html/im2006/watt/ . If there is no subdirectory named watt then an error is reported (something like, I can't find this website.) If it does find this directory, and the directory permissions are appropriately set, then it will reveal the contents of this directory. If there is a file named "index.html" in watt/ (I put a / after the name of a directory to indicate its nature) then it will open that file, and *not* reveal any other files in the directory, except those explicitly linked in the index.html.
The way Stuart Levy has rigged it, you and all other REU students have read-write(!)-execute privileges for all files in im2006/. You're supposed to write only into your own. But you can look into other directory and steal stufff you might want to edit in your own directory.
Now, when you log into new.math.uiuc.edu, by logging into any of the macs, or from a PC using an ssh "client" (i.e. an application that is designed to connect to new.math.uiuc.edu via the secure shell (ssh)). You will then find yourself in a different place on new, namely /b1/im2006/awatt2/. Despite the name "im2006" in the middle of the path, this is a different place than where the httpd is going to look for your stuff.
What to do?
Well, you can, each time do
Of course, you would soon forget what foo means, so we'll agree to give it a
sensible name. In your home directory (which is /b1/im2006/awatt2 but which
you can reach from anywhere by simple executing
One last item. Suppose you don't create a file watt/index.html just yet.
And suppose stuffe is really a neat picture, say neato.jpg, and you copy it
into your webspace. Why can't you see it in the browser? The reason is that
the security nazis have rigged it that when you take a screen-print, for
example, the unix permissions are such that only you can see it, not even
the httpd. To make stuff visible to the httpd you need to set permission thus
Of course there are "easier" ways to do this. But they are context specific. In a different context (machine, operating system, editor, browser) the shortcuts won't work. But Unix is universal, even in Windows lurks enough unix for these purposes (though it's much harder to figure out how to do it generically.)