In the July 2000 issue, Moshe Bar's article “Linux System Calls” contained information that I would like to correct. I suspect Moshe noticed by now that he was temporarily caught in a pre-i386 time warp when he stated, “This routine sets up an IDT (Interrupt Descriptor Table) with 256 entries, each 4 bytes long. It should be noted that the IDT contains vectors...” This is more a description of the pre-i386 IVT (interrupt vector table) than the IA32's IDT.
The IA32 uses another level of indirection. In particular, the IDT contains 8 byte descriptors which are either interrupt, trap or task gates. I suspect Linux uses the first two varieties. These gates contain the interrupt handler's 32-bit offset, some attribute bits and a 16-bit selector which references a code segment descriptor. In this case, that code segment descriptor is in the GDT (global descriptor table). This descriptor also consists of 8 bytes and vectors to the code segment containing the interrupt handler. The entry point for the handler is derived from the 32-bit offset lurking in the original IDT entry.
—Richard Sevenich firstname.lastname@example.org
I would like to express my support of more articles such as the one on WAP in the July issue. Recently, I was working on a WAP proof of concept for my organization. While I was motivated to move on the project, I was having difficulties taking the relatively new WAP standard and applying it in a straightforward manner to a commercial-quality proof of concept my organization would support. Mr. Mikal's article got to the meat of the issue and demonstrated how to get productive in the WAP space, while leveraging the skill sets that I, and other engineers here, already had. This one-page article got the ball rolling on producing my organization's wireless presence. In doing so, another organization has embraced open-source and free software. It is articles like this, and the knowledge sharing of the Linux community, that make magazines such as Linux Journal welcome in my cubicle.
Thanks to Mr. Mikal and Linux Journal.
—Brad Wheat email@example.com
When Linux began to grow in popularity, I jumped in, only to be put down by fellow Linux users. I used Linux on a Macintosh. As time went on and Linux distributions for the Mac grew, it became obvious that Linux users would have to acknowledge the Mac. But, rejection continued.
As a Mac user, I was aware of Linux before my PC pals. Apple had MKLinux, “an Apple thing”, I was told. Today, SuSE, the #1 distribution of Linux, is available for the PPC. I'll be merciful and not list all the others. After seeing the ads for PPC and Yellow Dog, it's nice to see a couple of articles, unlike the one degrading MKLinux in LJ a few months ago. Thank you.
—Calvin Bowen firstname.lastname@example.org
Two things on your Python supplement:
First, the uproar over the naked man. I honestly didn't notice he was naked. After reading the Letters column, I went back and looked; and sure enough, nothing but a bowtie. Considering how much I've seen Laura Croft (and I've never seen or played whatever video game she's in), it only seems fair that some computer magazine would have a naked guy.
As for Guido's pet language (haha! ha! oh never mind...), I must admit I think it's a bit lacking compared to Perl in one way. A fixable way, mind you; this isn't a fatal flaw type of thing. The problem is cpan—Python seems to be missing it. Perl has cpan; pretty much all Perl modules can be found on cpan and installed with the following steps:
perl Makefile.PL make make test sudo make install
Now, I've been looking at Python for a specific problem: I need to take data in a mySQL database and put it into a PostScript printer. Python seems to be able to communicate with mySQL, and its piddle module is both delightfully named and PostScript capable.
However, I still can't get mySQL connections to work, and the piddle install file was bordering on useless (but I got it working). I'll keep at it because I have to, but I think the Python development community should attempt to recreate (and perhaps improve) cpan. As a developer, I've found cpan to be one of the best practical systems to enable code reuse. In fact, the C, C++ and pretty much all development communities would be wise to create their own versions of cpan.
—Kevin Lyda email@example.com
I just got through reading all of the letters in the July 2000 issue from people complaining about the cover of the supplement. Big deal! I own a computer store smack down in the middle of the bible belt. I put all of my old magazines out front for customers to look at while I am working on their computers, and not one person has complained about the cover. I service people from all walks of life, parents, teachers, clergy, children, etc., and no one has taken offense to the publication...in fact, it has caused Windows-only kind of people to ask about Linux. Have even had a couple of converts because of it.
Regardless of what anyone else says...keep up the good work.
—Rodney Rees firstname.lastname@example.org
I read the July 2000 LJ Letters, which was dedicated to reader responses to your Python supplement cover in May. I could well remember that supplement which motivated me to add Python to my language collection. It never occurred to me that the cover picture was offensive.
Mind you, I am a university lecturer, and my pigeonhole is transparent. This picture which annoyed so many in the Western world went here, in an Asian, predominantly Buddhist country, unnoticed!
—Visvanath Ratnaweera email@example.com
Practical Task Scheduling Deployment
One of the best things about the UNIX environment (aside from being stable and efficient) is the vast array of software tools available to help you do your job. Traditionally, a UNIX tool does only one thing, but does that one thing very well. For example, grep is very easy to use and can search vast amounts of data quickly. The find tool can find a particular file or files based on all kinds of criteria. It's pretty easy to string these tools together to build even more powerful tools, such as a tool that finds all of the .log files in the /home directory and searches each one for a particular entry. This erector-set mentality allows UNIX system administrators to seem to always have the right tool for the job.
Cron traditionally has been considered another such a tool for job scheduling, but is it enough? This webinar considers that very question. The first part builds on a previous Geek Guide, Beyond Cron, and briefly describes how to know when it might be time to consider upgrading your job scheduling infrastructure. The second part presents an actual planning and implementation framework.
Join Linux Journal's Mike Diehl and Pat Cameron of Help Systems.
Free to Linux Journal readers.View Now!
|The Firebird Project's Firebird Relational Database||Jul 29, 2016|
|Stunnel Security for Oracle||Jul 28, 2016|
|SUSE LLC's SUSE Manager||Jul 21, 2016|
|My +1 Sword of Productivity||Jul 20, 2016|
|Non-Linux FOSS: Caffeine!||Jul 19, 2016|
|Murat Yener and Onur Dundar's Expert Android Studio (Wrox)||Jul 18, 2016|
- The Firebird Project's Firebird Relational Database
- Stunnel Security for Oracle
- My +1 Sword of Productivity
- Non-Linux FOSS: Caffeine!
- SUSE LLC's SUSE Manager
- Managing Linux Using Puppet
- Murat Yener and Onur Dundar's Expert Android Studio (Wrox)
- Parsing an RSS News Feed with a Bash Script
- Google's SwiftShader Released
- Doing for User Space What We Did for Kernel Space
With all the industry talk about the benefits of Linux on Power and all the performance advantages offered by its open architecture, you may be considering a move in that direction. If you are thinking about analytics, big data and cloud computing, you would be right to evaluate Power. The idea of using commodity x86 hardware and replacing it every three years is an outdated cost model. It doesn’t consider the total cost of ownership, and it doesn’t consider the advantage of real processing power, high-availability and multithreading like a demon.
This ebook takes a look at some of the practical applications of the Linux on Power platform and ways you might bring all the performance power of this open architecture to bear for your organization. There are no smoke and mirrors here—just hard, cold, empirical evidence provided by independent sources. I also consider some innovative ways Linux on Power will be used in the future.Get the Guide