HPR4574: UNIX Curio #0 - Introduction

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This series is dedicated to exploring little-known—and occasionally useful—trinkets lurking in the dusty corners of UNIX-like operating systems.

As the zeroth entry of this series, we'll have a little introduction to what it is supposed to be about and why you might want to listen. So that you don't leave without getting at least one piece of useful information, it will end with a little curio that you might find helpful someday.

Back in 2010, I was the editor of the newsletter, titled The Open Pitt, for the Western Pennsylvania Linux Users Group in Pittsburgh. We distributed it as a two-page PDF, so had to have enough material to fill each issue. Because we were having some trouble getting contributions, I started writing columns in a series called "UNIX Curio" to occupy the empty space. They were inspired in large part by examples I had seen of people re-inventing ways to do things when utilities for the same purpose had already existed for a long time.

The obvious question is: just what is a UNIX Curio? Let's start with the first word, UNIX. While a lot of people write it "Unix" instead, I have chosen to put it in all capitals because that is the way The Open Group, which controls the trademark and the certification process to use it, spells the word
¹
. The history of UNIX is complex (search online for more details
²
)—the short version is that many variants emerged, often introducing incompatibilities. Even within AT&T/Bell Laboratories, two major branches came out. The Research UNIX lineage, which includes Seventh Edition (sometimes called Version 7), was often used in universities and government while System III and its more popular successor System V were clearly intended as commercial products
³
. The University of California's BSD was also very influential. My intention is to talk about things that are relatively common; ideally, they would be present on a large majority of systems so you can actually
use
them.

Luckily, there were people who recognized the value in compatibility, so in the mid-1980s they initiated the development of the POSIX standards
⁴
. Publication of these not only caused commercial UNIX versions to aim for conformance—it gave Free Software implementations of utilities and operating systems a stable base to shoot for rather than having to chase multiple moving targets. As a result, today's GNU/Linux, FreeBSD, NetBSD, and OpenBSD systems generally behave as specified in POSIX, even if they haven't officially earned the UNIX or POSIX labels, so I treat them as part of the UNIX world.

Moving on to the second word, "curio," it just means "an object of curiosity, often one considered novel, rare, or bizarre." There are many well-used utilities in the UNIX world, but people forget about others because they are only useful in specific circumstances. And when those circumstances arise, these obscure ones don't always get remembered. One purpose of this series is to point out some of them and describe where they can be appropriately put to use.

With the flexible tools available on UNIX systems and the ability to string them together, it shouldn't be surprising that people come up with new ways to accomplish a task. I don't want to claim that these curios are always the
best
way to do something, just that it can be helpful to know they exist and see the way someone else solved the problem. Also, if you're using an unfamiliar system, sometimes programs you are accustomed to employing might not be installed so it's good to know about options that are widely available.

So why am I the person to talk about this subject? I am
not
a UNIX graybeard with decades of professional computing experience. If I did grow a beard, it would only be partially gray, and my working life has been spent in the engineering world mainly around safety equipment. Sadly, there I have been forced to use Windows almost exclusively. However, in my academic and personal pursuits, I have been involved with using UNIX and Linux for more than 30 years, so I do have a bit of a historical perspective. For some reason, when I encounter an unusual or obscure tool, I want to learn more about it, especially so if I find it to be useful in some way. After gaining that information, I might as well share it with you. In addition, I have been involved with Toastmasters International, a public speaking organization, for about 15 years so I have experience in presenting things orally. I was inspired to turn this article series into podcasts by murph
⁵
, who delivered a presentation at the 2025 OLF Conference describing how and why to contribute to Hacker Public Radio
⁶
.

The show notes for curios 1 through 3 will consist of the articles as they were originally written (though with references added). Because some examples, especially code, can be difficult to understand when they are read out loud, the podcasts will sometimes present the information in a different way. Show notes for this curio 0 and for curios 4 and later will be written with the podcast format in mind, so they will more closely match what I say.

Let's end with an actual curio to kick off the series. Have you ever needed a quick reminder about whether the file you're looking for can be found under the /usr or /var directories? On many UNIX systems,
man hier
will give you an overview of how the file hierarchy is organized. This manual page is not a standard, but was present in Seventh Edition UNIX
⁷
and many descendents, direct and indirect, including every Linux distribution I have ever used. There
are
attempts to standardize the layout; in the Linux world, the Filesystem Hierarchy Standard (FHS)
⁸
, now hosted by Freedesktop.org
⁹
, intends to set a path to be followed. It should be noted that systemd has its own idea of how things should be laid out based on the FHS; if it is in use, try
man file-hierarchy
instead as it will likely be a more accurate description.

I hope this gives you a good idea of what to expect in future episodes. The first one will be about shell archives, so keep an eye on Hacker Public Radio's schedule for it to appear.

References:

1. 
   
   The Open Group Trademarks
   https://www.opengroup.org/trademarks


2. 
   
   History of Unix
   https://en.wikipedia.org/wiki/History_of_Unix


3. 
   
   The Unix Tutorial, Part 3
   https://archive.org/details/byte-magazine-1983-10/page/n133/mode/2up


4. 
   
   POSIX Impact
   https://sites.google.com/site/jimisaak/posix-impact


5. 
   
   Correspondent: murph
   https://hackerpublicradio.org/correspondents/0444.html


6. 
   
   OLF Conference - December 6th, 2025
   https://www.youtube.com/watch?v=hyEunLtqbrA&t=25882


7. 
   
   File system hierarchy
   https://man.cat-v.org/unix_7th/7/hier


8. 
   
   Finding a successor to the FHS
   https://lwn.net/Articles/1032947/


9. 
   
   Freedesktop.org now hosts the Filesystem Hierarchy Standard
   https://lwn.net/Articles/1045405/

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