The joys of running a WordPress blog

Earlier today, John Duncan (of moonshine fame) emailed he was unable to post a comment to the previous post:
“I went to post a comment but somehow couldn’t convince the website to cooperate.”

There’s little point in maintaining a self-hosted blog if people cannot comment on it. If you tried, you got this scary message:

Catchable fatal error: Object of class WP_Error could not be converted to string in /wp-includes/formatting.php on line 1031

The days I meddled with wordpress core php-files are long gone, and a quick Google search didn’t come up with anything helpful.

In despair, there’s always the database to consider.

Here’s a screenshot of this blog’s database in phpMyAdmin:

No surprise you cannot comment here, there isn’t even a wp_comments table in the database! (though surprisingly, there’s a table wp_commentmeta…)

Two weeks ago I moved this blog to a new iMac. Perhaps the database got corrupted in the process, or the quick export option of phpMyAdmin doesn’t include comments (unlikely), or whatever.

Here’s what I did to get things working again. It may solve your problem if you don’t have a backup of another wordpress-blog with a functional wp_comments table.

1. Set up a new WordPress blog in the usual way, including a new database, let’s call it ‘newblog’.

2. In phpMyAdmin drop all tables in newblog except for wp_comments.

3. Export your blog’s database, say ‘oldblog’, via the ‘quick export’ option in phpMyAdmin to get a file oldblog.sql.

4. If this file is small you can use phpMyAdmin to import it into newblog. If not you need to do it with this terminal-command

mysql -h localhost -u root – p newblog < oldblog.sql

and have the patience for this to finish.

5. Change in your wp-config file the oldblog database to newblog.

Happy commenting!

From WordPress to ePublishing (1)

Perhaps, the tips and tricks I did receive to turn a selection of wordpress-posts into a proper ePub-file may be of use to others, so I will describe the procedure here in some detail.

It makes a difference whether or not some of the posts contain TeX. This time, I’ll sketch the process for non-LaTeX posts and hence we will turn the Bourbaki-code posts into ePub-format to read on your iPad, rather than merely into a pdf-file as last time. Next time, I’ll add some tricks to repeat this when some of your posts do contain LaTeX.

1. Install the ePub export plugin

Get the epub export wordpress plugin, install and activate it in the usual way. ePub Export automatically creates an ePub file when a post or page is published or updated. The ePubs are stored in the uploads directory. For later use, remember that your uploads directories are located under BLOGHOME/wp-content/uploads.

2. Update the posts you want to include

Decide which posts you want to include in your eBook, edit them (or not) and press for each one of them the update-button. This will populate today’s uploads-directory with a number of epub-files. Transfer them all, for example using Transmit, to a directory on your home-computer, named say MyFirstEBook.



3. Unpack the epub-files

The crucial fact to remember about epub-files is that they are really zipped archives containing xhtml-, css- and other files and directories. As we want to edit some of those, we first have to unpack the directories. So, change the .epub extensions to .zip and double-click on them to create the directories.



The crucial files in each directory are preface.xhtml (containing title author and blog-name), text.html (containing the blog-post) and the images-directory (containing copies of all the images used in the post).

4. Rename the directories user-friendly

As all the posts will be chapters in our eBook in some specific order, we will rename the numbers of the directories to something more user-friendly such as shortened blog-titles. To do this, double-click in each of the directories on the preface.xhtml file. This will open Safari and will show the title of the blog-post. Use it to rename that directory. For convenience let us call the directory corresponding to the first chapter in our book MasterDirectory

5. Move all images to the master directory

For each of the other chapter-directories, drag all the files contained in the images-subdirectory to MasterDirectory/images.

6. Edit the MasterDirectory/text.xhtml file

Because we will have to open and copy-paste all the text.xhtml files of the different directories, it is perhaps best to rename momentarily the MasterDirectory/text.xhtml file to something like master.xhtml.

Now, open this file with a text-processor such as TextWrangler. Edit it to remove unwanted html-code (such as links to other posts at the start if you are using the series-plugin, or previous/next post links at the end). Also add the title of the blog-post between h1-tags (and if you want to include a table of contents later, give it an anchor-name).

Go to the directory of your second chapter, open that text.xhtml file and copy/paste only the post-content over to the master-xhtml file at the appropriate place. As before, add title/anchor before the copied post-content.

Repeat this procedure, in order, for all the chapters of your eBook.

Once finished, doubleclick the master.xhtml file and correct remaining errors (as it is an xhtml-file, it is rather picky about opening and closing tags) and see whether all your images are included. If you’re satisfied with it, rename the master.xhtml to text.xhtml (don’t forget this!).

7. Edit the MasterDirectory/preface.xhtml file

Open the preface.xhtml file and change the first blogpost-title to the title of your booklet, alter your name (by default it uses your wp-nick) and add a frontipiece-picture if you so desire.

8. Re-package the directory into an epub-file

This is the (only) tricky part. E-book readers require that the mimetype file is the first one in the zip document. What’s more, to be fully compliant, this file should start at a very specific point – a 30-byte offset from the beginning of the zip file (so that the mimetype text itself starts at byte 38).

Here’s how to do this on a Mac (Linux-users being the geeks they are will have given up on reading this post a while ago and as to Windows-users, yeah well …). Open Terminal.app and cd to your MasterDirectory. Now type:

zip -X MyFirstEBook.epub mimetype

Next, type:

zip -rg MyFirstEBook.epub * -x *.DS_Store

(of course you’ll have to change your book-title to whatever you want). If you want to know more about these 2 magical commands, read this post.

9. Edit metadata

Get Calibre and add the MyFirstEBook.epub to Calibre by clicking on the ‘Add Books’ button.



You can preview your eBook by clicking on the ‘View’-button. Next, click the ‘Edit metadata’-button and alter the title and author entries (and whatever else you want to include) and click the OK button. Then click ‘Save to disk’.

10. Read your eBook on your iPad

Finally, we want to see how it looks on the iPad. Mail MyFirstEBook.epub to yourself as attachement, open it with iBooks and enjoy!

changes (ahead)

In view or recents events & comments, some changes have been made or will be made shortly :

categories : Sanitized the plethora of wordpress-categories to which posts belong. At the moment there are just 5 categories : ‘stories’ and ‘web’ (for all posts with low math-content) and three categories ‘level1’, ‘level2’ and ‘level3’, loosely indicating the math-difficulty of a post.

MathJax : After years of using LatexRender and WP-Latex, we’ll change to MathJax from now on. I’ll try to convert older posts as soon as possible. (Update : did a global search and replace. ‘Most’ LaTeX works, major exceptions being matrices and xymatrix commands. I’ll try to fix those later with LatexRender.)

theme : The next couple of days, the layout of this site may change randomly as I’ll be trying out things with the Swift wordpress theme. Hopefully, this will converge to a new design by next week.

name : Neverendingbooks will be renamed to something more math-related. Clearly, the new name will depend on the topics to be covered. On the main index page a pop-up poll will appear in the lower right-hand corner after 10 seconds. Please fill in the topics you’d like us to cover (no name or email required).

This poll will close on friday 21st at 12 CET and its outcome will influence name/direction of this blog. Use it also if you have a killer newname-suggestion. Among the responses so far, a funnier one : “An intro to, or motivation for non-commutative geometry, aimed at undergraduates. As a rule, I’d take what you think would be just right for undergrads, and then trim it down a little more.”

guest-posts : If you’d like to be a guest-blogger here at irregular times, please contact me. The first guest-post will be on noncommutative topology and the interpretation of quantum physics, and will appear soon. So, stay tuned…

NeB : 7 years and now an iPad App

Exactly 7 years ago I wrote my first post. This blog wasn’t called NeB yet and it used pMachine, a then free blogging tool (later transformed into expression engine), rather than WordPress.

Over the years NeB survived three hardware-upgrades of ‘the Matrix’ (the webserver hosting it), more themes than I care to remember, and a couple of dramatic closure announcements…

But then we’re still here, soldiering on, still uncertain whether there’s a point to it, but grateful for tiny tokens of appreciation.

Such as this morning’s story: Chandan deemed it necessary to correct two spelling mistakes in a 2 year old Fun-math post on Weil and the Riemann hypothesis (also reposted on Neb here). Often there’s a story behind such sudden comments, and a quick check of MathOverflow revealed this answer and the comments following it.

I thank Ed Dean for linking to the Fun-post, Chandan for correcting the misspellings and Georges for the kind words. I agree with Georges that a cut&copy of a blogpost-quoted text does not require a link to that post (though it is always much appreciated). It is rewarding to see such old posts getting a second chance…

Above the Google Analytics graph of the visitors coming here via a mobile device (at most 5 on a good day…). Anticipating much more iPads around after tonights presents-session I’ve made NeB more accessible for iPods, iPhones, iPads and other mobile devices.

The first time you get here via your Mac-device of choice you’ll be given the option of saving NeB as an App. It has its own icon (lowest row middle, also the favicon of NeB) and flashy start-up screen.

Of course, the whole point trying to make NeB more readable for Mobile users you get an overview of the latest posts together with links to categories and tags and the number of comments. Sliding through you can read the post, optimized for the device.

I do hope you will use the two buttons at the end of each post, the first to share or save it and the second to leave a comment.

I wish you all a lot of mathematical (and other) fun in 2011 :: lieven.