Letters

Correction

Regarding a quotation in “They Said It” in the January 2010 issue of LJ: “We act as though comfort and luxury were the chief requirements of life, when all that we need to make us happy is something to be enthusiastic about” is not by Einstein, but rather by Charles Kingsley. I'd give you a link, but it's easy enough to Google it yourself.

—
Jason Gade

He's correct, that should have been Charles Kingsley.—Ed.

Marconi?

I noticed on page 4 of the December 2009 issue that next month's issue will focus on Amateur Radio. The accompanying text reads “...Marconi's ushered in the era of radio communications...”. I hope a reputable publication such as yours is not going to perpetuate the myth that Marconi invented radio. There's no doubt he was brilliant at self-promotion, but he did not invent radio. Many people contributed to the development of radio technology, and Marconi was one of them. But if you insist on giving recognition to only one person, it should be Nikola Tesla. The US Supreme Court ruled in 1943 against Marconi and in favor of Tesla, deciding that Tesla's patent (645,576) had priority. Please do some fact-checking before perpetuating a ridiculous myth. Here's a few links to start with: en.wikipedia.org/wiki/Invention_of_radio, en.wikipedia.org/wiki/History_of_radio, en.wikipedia.org/wiki/Nikola_Tesla and en.wikipedia.org/wiki/Guglielmo_Marconi.

—
Jeff Harp

Bose?

In “When All Else Fails—Amateur Radio, the Original Open-Source Project” in the January 2010 issue, guest editor David A. Lane, KG4GIY, wrongly mentioned that Marconi invented radio. In fact, Sir J. C. Bose, the Indian scientist, was the true inventor of radio. He pioneered the iron filling coherer and lead galena crystal semiconductor receiver. Sir Bose invented the horn antenna and studied properties of refraction, diffraction and dispersion of millimeter and sub-millimeter waves. The above facts were published in the Proceedings of the IEEE a few years back. I am an Advanced Grade licensed Indian Radio Amateur and life member of the Amateur Radio Society of India for nearly three decades.

—
Ananda Bose, VU2AMB

David A. Lane replies: Ask 100 people who invented the radio, and of those who bother to answer, you will likely get one answer, and neither Tesla nor Bose will be it. Perhaps the paragraph should have read “...almost since Marconi popularized the thing...”. The truth is that history misremembers all the time, and the true geniuses are forgotten by those who come up with the reference implementations. Clearly, both Tesla and Bose contributed to the science that has led us to where we are today, just as much as Marconi and Motorola.

Webinars

I continually receive invitations to various Webinars on many topics and issues. Some don't suit me but many do. Here's the problem: my work schedule often prevents me from tuning in or participating at the time the Webinar is presented. I'd like to find a way to “record” these Webinars with all the video and audio, so that in the evening when back at home or on the weekend, I can sort through and watch the most pertinent of these events. Is this possible using Linux? Please advise!

—
Scott S. Jones

I feel your pain. There's a couple problems working against us with Webinars. One is that the format is far from standard. The other is that for some reason, many are specifically designed to be done only in real time. (I suspect those are specifically when demonstrations are happening in real time.) I don't think there's anything as Linux users we can do differently, apart from using a screen capture package at the onset of a Webinar. Ideally, they would be archived archive afterward, so we could watch at our leisure. We learned that ourselves here at Linux Journal. We did a live show (Linux Journal Live) that got many more views after the fact. Our schedules are just too full!—Ed.

Distance

Regarding Dave Taylor's column on calculating distance in the December 2009 issue of LJ, not knowing the number of bits of precision that your system offers, the solution still is quite easy.

The manner in which you converted from degrees to radians used M_PI. M_PI is a single-precision floating-point number “hard-coded” to the value of 3.141593. Whereas, a more precise representation of PI can be obtained by using 4.*atan(1.). (atan(1.) is the angle pi/4, so 4.*atan(1.) is equivalent to PI.

The modification has been made to Dave's code below, and it gives the correct result. As he mentioned in his article, this will give a 10% greater answer for the distance between the latitudes and longitudes, which Dave's code provided an answer of 917.984 miles:

#include <stdio.h>
#include <math.h>
#include <stdlib.h>

#define EARTH_RADIUS       (6371.0072 * 0.6214)
#define TORADS(degrees)    (degrees * (atan(1) / 65.))

main(int argc, char **argv)
{
   double lat1, long1, lat2, long2;
   double dLat, dLong, a, c, d;

   lat1  = TORADS(atof(argv[1]));
   long1 = TORADS(atof(argv[2]));
   lat2  = TORADS(atof(argv[3]));
   long2 = TORADS(atof(argv[4]));

   dLat  = lat2 - lat1;
   dLong = long2 - long1;

   a = sin(dLat/2) * sin(dLat/2) +
       cos(lat1) * cos(lat2) * sin(dLong/2) * sin(dLong/2);
   c = 2 * atan2(sqrt(a), sqrt(1-a));

   printf("%g\n", EARTH_RADIUS * c);
}

When I teach Bash, I regularly have students get information from the Web and process it via awk, sed and so on. Fun projects that I have used before are getting the current temperature for any city in the world, getting the headline news and getting current stock quotes. Thanks to Dave Taylor and Linux Journal, students are able to see that Linux/UNIX can do far more than Windows ever could dream of doing.

—
Paul J. Wilkinson

Dave Taylor replies: Great! Thanks for helping fine-tune the code.

Dark Days?

Every month, I read the Letters section, and more often than not, there is an end user who knocks Linux as being for “computer specialists” and not ready for the mainstream. I find this attitude unfortunate. With every release, distributions get better and better, and don't suffer from the constant barrage of malware, viruses and the like we see on Windows. In the December 2009 issue, a reader commented that “It's back to the dark days of MS-DOS all over again.” Dark days? I seem to remember back in the mid-1980s, DOS actually worked quite well. What gets me is that Microsoft continues to produce OSes and products that have numerous bugs and security flaws. Users are forced to license virus and malware scanners that are resource hogs and are doing a job that should have been prevented in the first place. Maybe we should all send a bill for our lost time in re-installing, scanning, cleaning and so on to Microsoft—they seem to have no issues collecting license fees. What about the hundreds of hours my staff has lost over the years?

—
George

Heck, I'd settle for just the hours spent trying to find drivers for hardware under Windows! I agree, it is sad people still see Linux as a difficult, cryptic, command-line-only operating system. It's still largely a matter of unfamiliarity. Many folks new to Linux are still overwhelmed by its nuances. The same can be said for people switching from Windows to OS X though, so I don't think it's really a Linux problem. I think we just need to keep pushing Linux in places it makes sense. As usual, my suggestion would be to start in schools!—Ed.

Waiting for Godot

Regarding Mitch Frazier's “Non-Linux FOSS” (December 2009): Explore2fs has been around for more than a decade. It works as designed, but development is slow. The write function has remained on the to-do list for most of the decade. I simply got tired of waiting. I found an excellent driver at www.fs-driver.org.

—
Peter Bratton

Slow or stalled development is often a fact of life with small open-source software projects, which is why it's important to help support projects you find useful. Note that the driver provided at www.fs-driver.org is freeware, but it is not open source.—Ed.

Peace Prize?

From the Portland Linux/UNIX Group e-mail list, by Keith Loftstrom:

Sounds like a great idea. What do you guys think?

—
Michael Rasmussen

A Peace Prize? For Linus? I dunno, I've read some of his posts to the kernel mailing list. Hehehe, all joking aside, I think the community Linus represents certainly deserves recognition. Since the prize goes to an individual, it does take some of the focus away from some other amazing contributors. That said, I could think of many worse recipients. He's got my vote!—Ed.

Security Tip

Mick, hope you enjoyed DEFCON, and excellent article in October 2009 issue of Linux Journal. It's moot now, but I thought I'd mention that when I travel, I edit my /etc/hosts file with entries for important DNS names (my bank, my Webmail and so on) to reduce the chance someone is spoofing them on an untrusted LAN. I comment out the entries when I get back home. I don't know if this really adds to my security, but I pretend it does. Thanks for the great work.

—
Paul

Mick Bauer replies: As a matter of fact, your /etc/hosts idea is an excellent one. DNS spoofing is an important part of many man-in-the-middle attacks, so being able to skip DNS lookups altogether when using untrusted networks definitely would be useful.

It also may be possible to run a local DNS-caching dæmon like nscd (which is commonly included in many distros by default), tuned in such a way that if you visited a given important site before you travel, your system will use its local cached lookup results instead of doing new DNS lookups while you're on the road. Thanks for passing on your idea and your kind words!

Decaf, Amazon EC2 on Android

As a longtime Linux Journal reader (I started when I was still studying more than ten years ago), I would like to draw your attention to decaf. decaf is an Android application for managing and monitoring your Amazon EC2 infrastructure. We were finalists in the Android Developer Challenge 2, resulting in a sixth place in the Misc. Category. (We were a bit disappointed but very proud to have come that far in the competition.)

We developed decaf primarily for ourselves, but we are trying to grow a community to make decaf development sustainable. I see that you covered Amazon EC2 multiple times, therefore, I think decaf might be of interest to your community.

You can read about decaf at decaf.9apps.net. I hope you find this interesting. If you have any questions, please ask.

—
Jurg van Vliet

Cool! Thanks Jurg. I just bought a Droid, so I'll have to check it out.—Ed.

Re: Ruby Articles

In response to the letter in the January 2010 issue regarding Ruby articles: I'd suggest looking into Clojure. It's a fairly new, Lisp-based language (it originally appeared in 2007 according to Wikipedia) that I first heard about from a professional Ruby programmer who now swears by it. He's written quite a few Clojure articles on his blog at briancarper.net/tag/clojure. Most of it is over my head as I've been out of the programming game for several years, but it has live code examples and might be an easier starting point than some dry manual or FAQ on clojure.org. Fun fact: that blog itself was written by Brian in Clojure.

Brian's a pretty easy guy to talk to and most likely would have some good recommendations on where to go to learn more about it or dig up material for an article.

As a side note, I'd personally be interested in seeing a roundup of all of the different languages that other LJ readers are no doubt sending e-mail messages about similar to this one even as we speak.

—
Marcus Huculak

Our next issue will have an interview with the creator of Clojure. And, perhaps we can get our Webmistress to put up a language poll on LinuxJournal.com. It would be great information to have!—Ed.

More on Ruby Articles

I had literally been right on the edge of writing a letter complaining about all the Ruby articles you've been printing for what feels like years now, when I saw MK's letter in the January 2010 issue. Naturally, I agree completely, and I'm afraid I'm going to stray into language-war territory here, but where's the Perl in LJ? If you're a sysadamin, it's invaluable, but for the Web programmers, what about all the progress around “modern” Perl with Moose, Catalyst, DBIC and so on? What about a regular look at the marvels of CPAN? I know it's kind of mythical, but how about some things on Perl6? I realize lots of languages exist, and frankly any break from Ruby would be good, but how about introducing new folks to the depth, breadth and future of Perl? Surely there aren't many languages more Linux than Perl? Still, I appreciate the magazine!

—
Steve Rippl

You make a good point, Steve. We'll see what we can do. (No, that's not a blow off, I promise!)—Ed.

Request

I would like to see a PHP program that searches an e-mail POP or IMAP, then automatically reports scams to abuse@live.com, abuse@gmail.com and so on. This program would find e-mail addresses in the body as well as the header. The report would inform the appropriate e-mail service were to find the e-mail address in the forwarded message. The program would delete the message from the inbox automatically. I have more than 150 domains that scam me all the time along with the free mail services to boot.

—
Stefan Ronnkvist

That sounds interesting, Stefan. I'd urge you either to start such a project or search around SourceForge to see if someone already has done the same. It sure beats forwarding them all by hand!—Ed.

Linux Mini vs. Mac Mini

I'm surprised I don't see Linux alternatives to a Mac Mini. The alternative hardware needs to be small and quiet (like Mac Mini). Hardware suppliers like Logic Supply and Polywell have a dizzying selection of hardware, but the cost is more than $1,000. Why isn't there a selection of “Linux Mini” alternatives equal or better than a Mac Mini at competitive prices?

For reference, a $600 Mac Mini (www.apple.com/macmini) features 2.26GHz Intel Core 2 Duo, 2GB DDR3 SDRAM, 160GB hard drive, gigabit Ethernet, 8x double-layer SuperDrive, NVIDIA GeForce 9400M graphics with dual video ports, USB and Firewire ports, Mac OS X Snow Leopard and 14 W power at idle.

—
greg bollendonk

I think one of the problems is that the demand is so low. For hardware companies, I think creating a Linux-based alternative to the Mac Mini would be possible, but they'd most likely sell more if they just made Windows terminals out of them.

One way to build a device like you're describing would be to soup up a thin client. There are a bunch of places that sell Linux thin clients that easily could have a hard drive added to them. Polywell, for example, has several thin-client options that are full-blown computers (at least one less than $200) just waiting for a Linux install.—Ed.

Photo of the Month

Have a photo you'd like to share with LJ readers? Send your submission to publisher@linuxjournal.com. If we run yours in the magazine, we'll send you a free T-shirt.

Here is a picture from our wedding on November 21, 2009 in Sarasota, Florida. Look at the tie! How cool is my wife? Submitted by Kevin P. Biggs.