Plan Files on AFS December 16, 2020

Something that you don’t see used too much anymore is the old finger program, which provides information on system users. You can also get information about users on other hosts, as long as the finger daemon is accepting requests on the remote server.

I think it used to be a fairly common practice to include a ~/.plan file in your home directory containing a brief description of your current plans. This allowed other users to see what you were up to when they looked you up with finger. According to a few CS grad student pages that I’ve found from the nineties, this also used to be a common practice at CMU.

I don’t know anyone who actually uses finger these days (the only people I could find with .plan files on the CMU system were old CS professors who have been here for decades), but I’m always up for a bit of neat Unix archaeology. I decided that it’d be fun to make a short .plan file for myself on AFS, so I went ahead and created one. When I was logged in to unix.andrew.cmu.edu and tried to look myself up, I got what was expected:

[ericzhen@unix.andrew.cmu.edu]$ finger ericzhen
           name:  Eric Zheng
          title:  Job Mgmt Student Job Profile
          class:  Sophomore
     department:  Computer Science

     login name:  ericzhen
       on since:  (whenever I logged in)

         e-mail:  ericzheng@cmu.edu

(contents of ~/.plan here)

However, when I tried from another system, this didn’t work. Even from another CMU machine, it didn’t work:

[ericzhen@angelshark.ics.cs.cmu.edu]$ finger ericzhen@andrew.cmu.edu
           name:  Eric Zheng
          title:  Job Mgmt Student Job Profile
          class:  Sophomore
     department:  Computer Science

     login name:  ericzhen

         e-mail:  ericzheng@cmu.edu

The ~/.plan file was missing! At first, I thought that this might just be because the finger daemon on the default Andrew Unix servers (serving from unix.andrew.cmu.edu) simply wasn’t display them, for privacy reasons or something similar. The CS professors whom I’d seen, by contrast, seemed to be serving things from *.cs.cmu.edu, which may not have this policy. This was a problematic hypothesis for me, since I did not have a way to log in to those machines; the Shark machines, like my favorite angelshark.ics.cs.cmu.edu, share a view of the AFS filesystem with Andrew Unix.

But I am stubborn, so I kept on trying to resolve this issue. I finally figured out the cause: the finger daemon wasn’t looking for a ~/.plan file, but rather for a ~/public/.plan file. After moving the file (just symlinking didn’t seem to work), I was able to get the results that I expected, even from my personal laptop, eric-debian:

[eric@eric-debian]$ finger ericzhen@andrew.cmu.edu
           name:  Eric Zheng
          title:  Job Mgmt Student Job Profile
          class:  Sophomore
     department:  Computer Science

     login name:  ericzhen

         e-mail:  ericzheng@cmu.edu

(contents of ~/public/.plan here)

You can also use finger ericzheng@cmu.edu (my CMUname alias), but this doesn’t display the .plan file.

Interestingly, you can also perform basic directory searches with finger, although it’s nothing that you couldn’t do with the university Web directory. For example, you can look people up by firstname.lastname@andrew.cmu.edu. Doing this for me, you get

[eric@eric-debian]$ finger eric.zheng@andrew.cmu.edu
(my info...)

Note that eric.zheng@andrew.cmu.edu is NOT my email address. It’s possible that mail sent there will get routed to me due to the rather Byzantine university mail redirection policies, but I wouldn’t count on it. Also, strangely the search for eric.zheng@andrew.cmu.edu and ericzhen@andrew.cmu.edu give different email addresses for me, although both are correct and route to the same mailbox.

Funnily enough, the entry for “Eric Zheng” directs straight to me. There is actually another Eric Zheng enrolled at CMU in the year below me, but to get his information you need to include the middle name:

[eric@eric-debian]$ finger eric.sabre.zheng@andrew.cmu.edu
(info for Eric S. Zheng, a freshman in MCS...)