Blog Entries

What's keeping that device in use?

Ever wonder what's keeping that device in use so you can't unmount it? It's happened to me a few times. The tool to discover this information? lsof.

Basically, you type something like: lsof /mnt/cdrom and it gives you a ps-style output detailing the PID and process of the processes that are using the cdrom. You can then go and manually stop those programs, or kill them yourself.

Continue reading...

PHP and Template Engines

On PhpPatterns, I recently read an article on Template Engines in PHP. It got my ire up, as it said (my interpretation):

  • "template engines are a bad idea"
  • "templating using PHP natively can be a good idea"
  • "template engines... are not worth the text their written in"

Okay, so that's actually direct quotes from the article. I took issue with it, immediately -- I use Smarty for everything I do, and the decision to do so was not done lightly. I have in fact been advocating the use of template engines in one language or another for several years with the various positions in which I've been employed; I think they are an essential tool for projects larger than a few pages. Why?

  • Mixing of languages causes inefficiency. When I'm programming, it's incredibly inefficient to be writing in up to four different languages: PHP or Perl, X/HTML, CSS, and Javascript. Switching between them while in the same file is cumbersome and confusing, and trying to find HTML entities buried within quoting can be a nightmare, even when done in heredocs. Separating the languages into different files seems not only natural, but essential.
  • Views contain their own logic. In an MVC pattern, the final web page View may be dependent on data passed to it via the Controller; however, this doesn't mean that I want the full functionality of a language like PHP or Perl to do that. I should only be doing simple logic or looping constructs -- and a full scripting language is overkill. (I do recognize, however, that template engines such as Smarty are written using PHP, so the language is being invoked regardless. What I speak of here is the language used to compose the template.)
  • Abstraction and Security. The fewer internals that are divulged on the template page, the better. For security purposes, I may not want clients able to know how data got to the page, only what data is available to them. In addition, if this data is abstracted enough, any number of backends could be connected to the page to produce output.

So, reading the aforementioned article really got my hackles up. However, it got me thinking, as well. One issue raised is that PHP can be used as your templating language. While I can understand why this might be desirable -- everything from load issues to flexibility -- I also feel that this doesn't give enough abstraction.

Using PHP seems to me to be inefficient on two fundamental levels, based on my understanding of The Pragmatic Programmer:

  • Domain Langauge. The Pragmatic Programmer suggests that subsets of a language should be used, or wholly new mini-languages developed, that speak to the domain at hand. As an example, you might want to use a sharp tool to open a can; an axe would be overkill, but a knife might work nicely. Using PHP to describe a template is like using an axe to open a can; it'll do the job, but it may also make a mess of it all, simply because it's too much sharp edge for the job.
  • Metadata. Metadata is data about data; to my thinking, templates describe the data they are communicating; the compiled template actually contains the data. In this regard, again, putting PHP into the script is overkill as doing so gives more than just some hints as to what the data is.

The author of the article also makes a case for teaching web designers PHP -- that the language is sufficiently easy to pick up that they typically will be able to learn it as easily, if not more easily, than a template language. I agree to a degree... But my experience has shown that web designers typically struggle with HTML, let alone PHP. (Note: my experience in this regard is not huge, and I'm sure that this is an exaggeration.) I find that it's typically easiest for me to give an example template, explain what the funny, non-HTML stuff can do, and let them go from there. Using this approach, they do not need to learn anything new -- they simply work with placeholders.

Still, I think the author raises some fine points. I wish he'd bothered to do more research into why people choose template engines and the benefits that arise from using them before simply outright slamming them. Of course, the article is also a bit dated; it was written over two years ago, and much has changed in the world of PHP and many of its template engines. I'm curious as to whether they would feel the same way today.

Me? My mind is made up -- the benefits, in my circumstances, far outweigh any costs associated. I'll be using template engines, and Smarty in particular, for years to come.

Continue reading...

Binary packages for Gentoo

I'd read that you could get binary packages for gentoo, thus alleviating the need to compile everything. (Of course, then you lose some of the benefits of compiling everything, but you gain in speed...) Unfortunately, I mistook this with ebuilds, and never quite figured it out.

The key is to throw the -g flag:

    % emerge -g gnumeric # which is like 'emerge --getbinpkg gnumeric'

I also learned how to update packages tonight:

    % emerge sync             # to sync your mirror with the gentoo mirrors
    % emerge --update portage # if necessary
    % emerge --update system  # updates core system files
    % emerge --update world   # updates all packages 

Continue reading...

Gentoo for several weeks

I've had a bunch of problems with my new computer -- it uses ACPI, but if I load the ACPI modules, it won't boot; if I don't load them, I have to go through contortions to get the ethernet working, and it won't power down; and a bunch of other little stuff.

So, a few weeks ago, I thought, what the heck? Why not try Gentoo? I've been reading about it since it first came out, and I remember talking with Duane about it once, and it has a reputation for both being cutting edge and stable. Heck, even Wil Wheaton's endorsing it... it can't be all bad, right?

I had a few misstarts -- bad CDs, not quite getting how the chroot thing worked, problems with DNS (which I still don't understand; and Rob has them as well, so it's not just me). But once I got it installed... well, I'm impressed.

The thing about Gentoo is, it compiles everything from source. It's like Debian, in that it fetches all dependencies and installs those... but it's all source. So it's not exactly fast. But because everything is compiled, and because you setup C flags specific to your machine, what you get is incredibly optimized for your own machine. This 1.6GHz machine simply flies. And the memory usage just stays low.

I'd like to use it for my server... but I can't really take the server down at this point when it's making both my mom and myself money. But what a great system... I only wish I'd used it for the mail server at work.

Continue reading...

Cgiapp: A PHP Class

After working on some OO classes yesterday for an application backend I'm developing for work, I decided I needed to create a BREAD class to make this simpler. You know, Browse-Read-Edit-Add-Delete.

At first, I figured I'd build off of what I'd done yesterday. But then I got to thinking (ah, thinking, my curse). I ran into the BREAD concept originally when investigating CGI::Application; a number of individuals had developed CGI::Apps that provided this functionality. I'd discarded them usually because they provided more functionality than I needed or because they introduced more complexity than I was willing to tackle right then.

But once my thoughts had gone to BREAD and CGI::App, I started thinking how nice it would be to have CGI::Application for PHP. And then I thought, why not? What prevents me from porting it? I have the source...

So, today I stayed home with Maeve, who, on the tail end of an illness, evidently ran herself down when at daycare yesterday, and stayed home sleeping most of the day. So, while she was resting, I sat down with a printout of the non-POD code of CGI::App and hammered out what I needed to do. Then, when she fell asleep for a nap, I typed it all out and started testing. And, I'm proud to say, it works. For an example, visit my development site to see a very simple, templated application in action.

Continue reading...

B. Gates: Open Source Programmer?

I just read coverage of a panel of programming luminaries on Salon; the topic of discussion was about the state of programming. In the course of the discussion, the subject of Open Source came up. Several of the luminaries -- which included architects of the Mac OS and Windows, as well as others -- derided the community for basically reinventing the wheel, and wheels that need to be re-thought entirely anyways. One questioned, "Why is hte idealism just about how the code is shared -- what about idealism about the code itself?"

Andy Hertzfeld (who helped develop the original Mac OS) was sitting on the panel, and jumped in. He has been working with Eazel and Chandler in recent years, and thus has an inside view of open source. His initial comment: "It's because they want people to use the stuff!" Basically, they program Windows- or Mac-like interfaces because then people will be willing to try it out. They program office suites because people "need" an office suite to be productive. Such offerings hook them into the OSS movement.

Another participant, Dan Bricklin (of VisiCalc, a pioneering spreadsheet program) shared an anecdote from Bill Gates. Evidently, Gates gave an interview (with Lammers -- look up this person) in which he explained that his work on MS's BASIC compiler was done by looking at how other programmers had accomplished the task. In his own words, "The best way to prepare is to write programs, and to study great programs that other people have written. In my case, I went to the garbage cans at the Computer Science Center and I fished out listings of their operating systems."

So basically, Gates was an early adopter of OSS methodologies... Interesting to see that today he's so protective of MS code. Guess money might do that to you.

Continue reading...

POD for PHP

I was lamenting at work the other day that now that I've discovered OO and templating with PHP, the only major feature missing for me is a way to easily document my programs. I'm a big fan of perl's POD, and use it fairly extensively, even for simple scripts -- it's a way to provide a quick manual without needing to worry too much about how to format it.

So, it hit me on the way home Friday night: what prevents me from using POD in multiline comments of PHP scripts? I thought I'd give it a try when I got home.

First I googled for 'POD for PHP', and found a link to perlmongers where somebody recounted seeing that exact thing done, and how nicely it worked.

Then I tried it.. and it indeed worked. So, basically, I've got all the tools I love from perl in PHP, one of which is borrowed directly from the language!

Continue reading...

Scrap that. We're gonna' use PHP

I've been researching and coding for a couple months now with the decision that I'd rewrite the family website/portal using mod_perl with CGI::Application. I still like the idea, but a couple things recently have made me rethink it.

For starters, the perl DBI is a bit of a pain to program. At work, I've become very accustomed to using PEAR's DB library, and while it's in many ways derived from perl's DBI, it's much simpler to use.

Then there's the whole HTML::Template debacle. There's several ways in which to write the templates, but they don't all work in all situations, and, it seems they're a bit limited. We've started using PHP's Smarty at work, and it's much more intuitive, a wee bit more consistent, and almost infinitely more extendable. I could go the Template::Toolkit route for perl, but that's almost like learning another whole language.

Then, there's the way objects work in perl versus PHP. I've discovered that PHP objects are very easy and very extendable. I wouldn't have found them half as easy, however, if I hadn't already been doing object oriented programming in perl. One major difference, however, is how easy it is to create new attributes on the fly, and the syntax is much easier and cleaner.

Add to that the fact that if you want to dynamically require modules in perl, you have to go through some significant, often unsurmountable, hoops. So you can't easily have dynamic objects of dynamically defined classes. In PHP, though, you can require_once or include_once at any time without even thinking.

The final straw, however, was when I did my first OO application in PHP this past week. I hammered it out in a matter of an hour or so. Then I rewrote it to incorporate Smarty in around an hour. And it all worked easily. Then I wrote a form-handling libary in just over two hours that worked immediately -- and made it possible for me to write a several screen application in a matter of an hour, complete with form, form validation, and database calls. Doing the same with CGI::Application took me hours, if not days.

So, my idea is this: port CGI::Application to PHP. I love the concept of CGI::App -- it's exactly how I want to program, and I think it's solid. However, by porting it to PHP, I automatically have session and cookie support, and database support is only a few lines of code away when I use PEAR; I'll add Smarty as the template toolkit of choice, but make it easy to override the template methods to utilize . I get a nice MVC-style application template, but one that makes developing quickie applications truly a snap.

This falls under the "right-tool-for-the-job" category; perl, while a wonderful language, and with a large tradition as a CGI language, was not developed for the web as PHP was. PHP just makes more sense in this instance. And I won't be abandoning perl by any stretch; I still use it daily at work and at home for solving any number of tasks from automated backups to checking server availability to keeping my ethernet connection alive. But I have real strengths as a PHP developer, and it would be a shame not to use those strengths with our home website.

Continue reading...

PHP Class Tips

We're starting to use OO in our PHP at work. I discovered when I started using it why I'd been having problems wrapping my head around some of the applications I've been programming lately: I've become accustomed in Perl to using an OO framework. Suddenly, programming in PHP was much easier.

There's a few things that are different, however. It appears that you cannot pass objects in object attributes, and then reference them like thus:

    $object->db>query($sql)

PHP doesn't like that kind of syntax (at least not in versions 4.x). Instead, you have to pass a reference to the object in the attribute, then set a temporary variable to that reference whenever you wish to use it:

    $object->db =& $db;
    ...
    $db = $object->db;
    $res = $db->query($sql);

What if you want to inherit from another class and extend one of the methods? In other words, you want to use the method from the parent class, but you want to do some additional items with it? Simple: use parent:

    function method1()
    {
        /* do some pre-processing */

        parent::method1(); // Do the parent's version of the method

        /* do some more stuff here */
    }

Update:

Actually, you *can* reference objects when they are attributes of another object; you just have to define the references in the correct order:

    $db =& DB::connect('dsn');
    $this->db =& $db;
    ...
    $res = $this->db->query($sql);

I've tested the above syntax with both PEAR's DB and with Smarty, and it works without issue.

Continue reading...

Making a RAID array from the command line

Last night, I created my first RAID array from the commandline. It was quite simple, I discovered.

  1. Create your partitions using fstab. Remember, primary partitions must be created before extended partitions.
  2. Look in /proc/partions and note the new partition IDs.
  3. Edit /etc/raidtab and create a new RAID array. If unsure of the syntax, look up the Linux Software RAID HOWTO for more details.
  4. Type mkraid /dev/md?, where ? is the id of the RAID device you just entered in /etc/raidtab.
  5. Format the new RAID device with your favorite filesystem, assign it a mount point, and start using it!

I was impressed with how easy it was; the choices that the Anaconda installer present for creating a RAID array made it seem like the underlying process must be difficult, when in fact it may have been almost the same complexity if not easier.

Continue reading...

<< First | < Previous | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | Next > | Last >>