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In Bill Childers' “Virtualization Shootout: VMware Server vs. VirtualBox vs. KVM” in the November 2009 issue, there's a mistake: KVM does support headless VNC. That's the way I use it in a Debian server to have a Win Server VM for hosting an antivirus server for Win PCs, not available for GNU/Linux.

Dani Gutiérrez

Bill Childers replies: I indeed made a mistake when doing the research for this article. (Don't let Kyle Rankin know, I'll never hear the end of it!) Turns out, you can get a VNC-enabled console simply by adding a -vnc :1 switch when starting your KVM virtual machine. Sadly, when doing research for the article, my Google-fu failed me—I kept getting instructions for the “KVM” type of keyboard/video/mouse switches. I'm glad it supports headless mode, and I'm sorry I missed that in my research. However, this does highlight the issue that KVM's usability isn't where it should be to compete with VirtualBox and VMware on that playing field. This is a moving target though, and I'm confident the developers will continue to improve KVM.

Ruby Articles

I have been a dedicated Linux Journal reader for many years and generally like the mixture of different topics. However, in recent months, I've grown more and more annoyed with the series of Ruby articles. Reuven M. Lerner is doing a good job. It is not about the quality of his work; it is about choosing the right topics for the magazine. Ruby is not by any means the most popular language (www.langpop.com) in either the open-source or commercial space. I think it is time to yield magazine space to other programming languages.


You are absolutely correct in regard to Ruby not being the most popular language in use. I think it might be the current state of the language's maturity that is sparking so much interest. I'm not a programmer at all (well, the occasional bash script, but that doesn't count), so I asked a similar question a while back. Reuven's column is still very highly rated by our readership. Although Ruby may not be the most popular language, it does appear to garner a lot of interest. I can only assume that, in time, it will pass, and the next fancy language will take its place. In the meantime, thank you for the letter. I'm sure Reuven will read it and keep an ear out for what is most sought after.—Ed.


I recently installed Sun's VirtualBox after reading the “Virtualization Shootout” article in the November 2009 issue. It's a great tool that allows me to keep Windows set up for those occasions when I can't figure out how to do something in Linux. As a relative newbie who works in an all-Microsoft environment, I wasn't getting the exposure to Linux I wanted, because I had to dual-boot between the two OSes. Virtualization gives me the best of both worlds. So, now I boot only to the Ubuntu Linux host and open my virtual Windows XP guest system when needed.

I love your magazine and look forward to every issue. I read all the columns, most of the reviews and at least scan the Indepth articles. Every month, I find new information and ideas I use to grow in my understanding of Linux. Next year, I plan to install Linux from scratch for the knowledge it will bring. Thanks again for the all information and expertise you pack into every issue.

Paul West


I know you get lots of e-mail messages saying “why don't you write about ...”, but I will add this for the record: take a look at Zarafa—it's a fully native Linux-compatible GPLv3 groupware alternative for Exchange with Outlook support at no extra cost!

I have spent approximately four years researching GPL groupware solutions and have tried several (Scalix, eGroupWare, Zimbra, Citadel and Open-Xchange), but none of them come close to matching the features and support of this app. It does calendaring, task lists, contacts, e-mail, BlackBerry and mobile phone sync. It's easy to deploy, and it sits on top of your own server's MTA.

I don't work for the company, nor do I sell any of its stuff, but it is a very cool application! Check it out, and maybe you could do a review for your readers (www.zarafa.com).

Trent Murray

Darn it Trent, now you've given me another toy to play with! Thanks for the tip; I'll be sure to check it out. I too have been looking for a full-featured groupware option.—Ed.

Reader Ramblings

I am a bit of a newbie to Linux, although some of my computing days go back to systems using 12AT7 (tubes!) as memory elements. I am also a radio amateur, as you probably can guess from my e-mail address. I have had a few pleasant surprises since switching from the offerings coming out of Washington state. I recently connected an ICOM 7200 to an Ubuntu box and found the USB drivers were already present. Nice! I installed Fldigi, changed the CI-V address on the 7200 to 6E, set Fldigi for Hamlib mode and told it I was using an ICOM 756ProIII (there is no definition yet for the 7200), and all things worked. Try that with the competition! I could add a few other nice things, but this letter would be a bit long.

Incidentally, I got my first copy of Linux Journal on a draw from the Manitoba UNIX User Group, of which I am a member.

I became rather disgusted with you know who a few years ago, after finding that Encarta 2001 would not run under XP. It seems XP does not maintain backward compatibility with earlier releases. I get the impression that a certain company has the idea of releasing a new OS version every few years, with no capability of running on anything less than the latest hardware and then discontinue the support for the older OS, and everybody has to upgrade. $$$$! I realize that the days of the 4.77MHz XT are long gone, but a system using a 1.5GHz Intel P4M isn't too shabby, and a version from a well-known manufacturer apparently will have problems with the new “7” when it comes out.

One thing I would like to see as a beginner is a “newbies column”, where those of us who are green at Linux can learn the fundamentals of the system. Ubuntu Kung-Fu by Keir Thomas was another prize and a big help to me.

Gerald K. Sherman

I'm a fairly geeky guy, but I must admit you out-geeked me with Fldigi'd Hamlibs and such! But as luck would have it, this issue's Features are all related to Amateur Radio—hope you enjoy the articles. We try to keep the content in the magazine diverse enough to reach everyone, but I'll admit some of the articles are even over my head. You should check out our Web site, which has many more articles and some helpful videos often aimed at new users. Either way, we'll continue to try reaching all user levels in the print magazine. If Linux Journal starts to no longer be useful and fun, be sure to call us out!—Ed.

awk Tip

This is in reference to Dave Taylor's column in the April 2009 issue on word and letter counts. The filter used for counting occurrences of patterns on stdin is:

sort  | uniq -c

I appreciate the beauty of this filter owing to its simplicity. In practice though, I find this becoming slower and slower as the data size increases and the cost of sorting increases. I use the following code, which does the job extremely fast:

awk ' { CNT[$0]++ }
END { for (i in CNT) print i, CNT[i] }

One also can derive probability of occurrence easily as:

END { for (i in CNT) print i, CNT[i]/length(CNT) }

I appreciate that the focus of this column is mainly on the shell, although I felt that a couple lines of awk is not bad for the above problem, as it avoids sort, which can be costly at times. (I'm not sure whether the use of associative arrays in bash would be equally compact.)

Mayuresh Warunjikar

Dave Taylor replies: Good use of awk, Mayuresh. My goal is always to show what's quick and fast—not always what's most efficient or highest performance. Sometimes that means it doesn't scale well, but frankly, my view of shell script programming is that most scripts break down once you really push hard on them anyway, at which point it's smart to rewrite it into a faster, more powerful app.


Recently, I created a tool to help sysadmins like myself—ones that love Linux!—to be able to download their Microsoft Exchange mail using HTTP Outlook Web Access. It downloads e-mail, formats e-mail properly to match .mbox file format and appends additional headers. Then, you can view your mail through the console. Maybe it will interest some of your readers. It is absolutely free, GPLv3, and it works very well. See www.isrcomputing.com/msfetch. Love your journal, by the way.

Paul Grinberg

Neat Paul! We'll have to check it out. Thanks for the link.—Ed.


In “Exploring Lat/Lon with Shell Scripts” [November 2009], Dave Taylor writes, “To accomplish any sophisticated mathematics in a Linux shell, we're pretty much stuck with bc.” No! Shed your stone tools! Throw off your bc and dc chains! There is a better way. The clac utility is available at clac.sourceforge.net, and it has the following features:

  • Handles trig, complex math, log and so on.

  • Supports infix expressions (no Reverse Polish jokes, please).

  • Uses Python underneath (Python syntax welcome, but not required).

  • Single source file—take it where you need it.

  • User-extensible via Python: import/write the modules you want.

  • Script-friendly: expression(s) via arguments or stdin, evaluation printed to stdout.

clac takes expressions like:

"round( degrees(phase( e** ( 2j ) ) ) )"
"sum([ x**2 for x in ( $CSV ) ] )"

and does what you would expect a CLI tool to do: prints out the answer in a fraction of a second.

Mark Allen Borgerding

Dave Taylor replies: Cool, thanks for bringing that to our attention!

Closed Captioning

Regarding the letter asking for transcripts of the video Tech Tips on LinuxJournal.com in the November 2009 issue: I agree that they would be pretty much useless; however, CC (closed captioning) would be very useful! Those us us who would like to watch a very relevant and work-related video in our office without speakers and Linux users who are hearing impaired really would appreciate captions. Please consider adding captions to your otherwise awesome videos.

Jon Harrell

You're not the first (or second, or third, or twelfth) person to ask for something like this. I will keep trying to figure out a way to make closed captioning, or something similar, a feasible addition to the Tech Tips. Perhaps we should open it up to the readership to submit CC files to go along with the OGG videos. In fact, that's a really neat idea. I'm glad we had this talk!—Ed.

Photo of the Month

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

Here's a photo of my five-year-old daughter who found your issue on Linux security especially interesting—submitted by Mattias Villani.

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