Category: Tips

LaTeX for TiddlyWiki – A MathJax Plugin

Update: The MathJax Plugin for TiddlyWiki has a new home: https://github.com/guyru/tiddlywiki-mathjax
Some time ago I came across MathJax, a nifty, Javascript based engine for displaying TeX and LaTeX equations. It works by “translating” the equation to MathML or HTML+CSS, so it works on all modern browsers. The result isn’t a raster image, like in most LaTeX solutions (e.g. MediaWiki), so it’s scales with the text around it. Furthermore, it’s quite easy to integrate as it doesn’t require any real installation, and you could always use MathJax’s own CDN, which makes things even simpler.

TiddlyWiki with the MathJaxPlugin
A tiddler with LaTeX equations.

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Using Monospaced Font in the TidddlyWiki Editor

By default, TiddlyWiki uses its default fonts (Arial or Helvetica) for it’s tiddlers editor. While these fonts are more than fine as default font for the text in tiddlers, I found it much less convinient when editing tiddler’s. Furthermore, it’s even a bad choice when one has code snippets in his tiddlers.

The following code snippet solves the problem by resetting the font used in the editor to monospaced font. Just add the following snippet:

/*{{{*/
.editor {
    font-family: DejaVu Sans Mono, Courier New, monospace;
}
/*}}}*/

To your StyleSheet tiddler (or create it if it doesn’t exist yet). Now the next time you’ll edit a tiddler you will do it using a monospaced font.

Temporary Disabling Bash History

Say that you’ve got to pass some password as command line argument to something. It would probably be a bad idea to store it in your ~/.bash_history, but clearing the file isn’t desired either. So you need to temporary disable the command history for the current session. You can do it by unsetting the HISTFILE environment variable.

unset HISTFILE

The result is that while the session is active you can access the history as usual, but it won’t be saved to the disk. History for other sessions, will behave as usual.

iproute2 Cheatsheet

The iproute2 package offers the ip utility, which is a modern replacments for tools such as ifconfig, route, arp and more. It allows to configure addresses, links route and arp tables. The only problem is that its documentation can be quite confusing. This post is intended to be a task-oriented guide to this utility, it’s far from complete and I intend to update it from time to time.
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Kernel Configuration and nvidia-drivers

This is more of a note to myself, as I keep forgetting this. The propriety NVIDIA drivers, provided by the x11-drivers/nvidia-drivers dislikes alternatives. It will refuse to build against a kernel with the rivafb (CONFIG_FB_RIVA) and nvidiafb (CONFIG_FB_NVIDIA) built in or built as modules. Both can be found (and unset) under:

Device Drivers
-> Graphics support
   -> nVidia Framebuffer Support
   -> nVidia Riva support

Eject Your Kindle and Reconnect under Linux

I am Your User suggested a method to eject your Kindle in Linux. While his method works, you don’t need to specify the partition number. E.g.

$ sudo eject /dev/sdd

where /dev/sdd is the device file of the Kindle.

But what if you want to reconnect it back without plugging in and out the usb cable? You can add the -t switch.

$ sudo eject -t /dev/sdd

Even though it prints the following error:

eject: CD-ROM tray close command failed: Input/output error

it works, and the Kindle reappears in KDE.

Deleting Comments from Tickets in Trac

Spammers apparently love Trac. After trying to fighting spam tickets and later installing the SpamFilter plugin, I’ve managed to control spam tickets in the Open Yahtzee Trac site.. But now spammers started spamming in the ticket comments. The bad news is that Trac (at least in version 0.11) doesn’t have built-in facilities to completely remove ticket comments.


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URL-Safe Timestamps using Base64

Passing around timestamps in URLs is a common task. We usually want our URLs to be as shortest as possible. I’ve found using Base64 to result in the shortest URL-safe representation, just 6 chars. This compares with the 12 chars of the naive way, and 8 chars when using hex representation.

The following Python functions allow you to build and read these 6 chars URL-safe timestamps:
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