K-Squared Ramblings

When digiKam Failed to Connect

In the decade I’ve been using Linux, it’s gone from something that required lots of technical know-how just to set up, to something that (in its major flavors) can auto-detect most hardware and provides friendly GUIs for most configuration tasks. But every once in a while, I have the kind of experience that would turn a new user off of Linux. Usually because Fedora has decided to change something during an update.

In this case, it was a digital camera problem. Since we bought our Canon PowerShot SD600 last December, I’ve used KDE’s digiKam to transfer and manage the photos. DigiKam detected the camera and accessed the photos right out of the box, no configuration needed beyond telling it to remember the model. But something changed in the last two weeks, and last night I started getting an error message: Failed to connect to the camera. Oddly enough, it could still detect the camera when it was connected. But it couldn’t display or download the images.

I searched all over, hitting dead end after dead end, until I got a hint that it was a permissions problem. Read the rest of this entry »

Generic Novel-ty

Found this on Amazon a few months ago while looking for something by Neil Gaiman:

I just checked back and the listing is gone. I figure it was probably a placeholder or something.

“Expected dict” Errors in FDF Acrobat Forms

Today I was trying to fix a problem in a section of a website that hadn’t been changed in roughly 5 years. The page in question retrieved data from a database and filled out an Acrobat form using FDF. Under some circumstances, Adobe Reader would generate an error message, “Expected a dict object.” Then it would freeze, and crash the web browser for good measure.

This site was built with ColdFusion, and used a then-freely-available library called PDFFormFiller.cfm (I can’t find any sign of it now) to generate the FDF code. After saving the offending FDF to a file (eliminating the browser as a factor), I started manually editing the code to see what happened.

The problem turned out to be parentheses appearing in the form data. FDF uses parentheses-delimited strings, and it was finding ) in the code and trying to parse what was left as FDF tokens. The solution was simple: just escape the parentheses as \( or \). Read the rest of this entry »

Apache, mod_ssl, and syntax errors in krb5.h

Upgraded the Apache web server today. I’d forgotten about a problem compiling mod_ssl on some systems. Fortunately I had left myself a note about it.

If you get syntax errors in krb5.h while trying to build Apache with mod_ssl, it’s probably because your Linux distribution puts the Kerberos include files in their own subdirectory (Red Hat/Fedora and derivatives do this), and the configure script has somehow missed them.

Solution: Configure mod_ssl and Apache as normal. Then edit the file path_to_apache_source/src/modules/ssl/Makefile. Look for the CFLAGS1 line and add -I/usr/kerberos/include to it.

Then continue with the build as normal.

We now return you to your regularly scheduled blog.

Open Letter to WordPress Plugin Authors

Please, when developing your plugins, be sure to always use the full opening tag for PHP:

<?php code goes here ?>

On some servers—maybe even your own—you can shorten this to just the opening <?. The following line in php.ini will disable this “feature,” and many web server administrators do so to simplify things like generating XML with PHP:

short_open_tag = Off

When this option is set, PHP will ignore <? and assume it’s simply part of the template… along with all the code following it. If you’re lucky, it means a bunch of PHP code gets sent to the web browser. If you’re not lucky, it results in invalid syntax, and PHP grinds to a halt, spitting out a blank page and a PHP Parse Error.

So please make sure you always use the full opening tag so that your plugin will be compatible with everyone’s system. If you run your own server, set that option in php.ini so that if you miss one, you can catch it before you post it.