George MacKerron: code blog

I recently switched to TextMate for editing Stata .do files: unlike Stata’s built-in editor on the Mac, it has syntax highlighting and other goodies via Timothy Beatty’s bundle.

One thing it doesn’t have, though, is tab completion. Or rather, it didn’t, until now.

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Ordnance Survey’s Code-Point with Polygons “provides a precise geographical location for each postcode unit in Great Britain”. It’s available in various formats, including ESRI .shp files.

Many UK academics can access the data via institutional subscription to EDINA Digimap. I’m using it in my research into subjective wellbeing and environmental quality.

This post shows how to:

1. import the data files into a PostGIS database; and
2. de-normalise the data into a single table, where there’s a one-to-one mapping of postcodes to rows, and each row contains either all geographical locations covered by a postcode (as a single geometry column, of type multipolygon) or the reason why no such location is available

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I have a simple site that generates covers for CDs I burn from iTunes purchases and so on (it pre-dates widespread use of JS libraries, and is in much need of prettifying). The site uses Amazon Product Advertising API calls to search and retrieve album cover art and track listings. Since earlier this month, such API calls have to be cryptographically signed.

This is somewhat annoying — the site’s original design has it communicating independently with Amazon (using Amazon’s XSLT API feature to transform their XML data into JSON), and that’s no longer possible with the use of a private key. But it’s not unfixable. The site now sends its API call first to my server, which returns a signed version, and then forwards the signed call on to Amazon.

I found most of what I needed for this on Chris Roos’ blog, but his version still wasn’t quite working for me (the two problems I recall are that Ruby’s CGI.escape doesn’t quite follow Amazon’s requirements, and that times need converting to GMT).

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Until Monday, O2 is offering a half-price USB dongle for pay-as-you-go mobile broadband. Buy it via Quidco, and you get not only the dongle but also a month’s access (or 3GB, whichever is the sooner) absolutely free.

So: free modem. No further commitment. And the opportunity to buy access a day at a time for £2, on a train journey, for example, or in an airport lounge, where the cheapest paid-for WiFi option is rarely less than £5, and often nearer £10. Handy.

Update. O2 is no longer doing the modem at half price, but the Quidco cashback has increased so that it still fully covers the modem and a £15 top-up.

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Between Time Machine and services like Dropbox, paranoid levels of backup are surprisingly painless to achieve on the Mac these days.

Still, just one more copy of your data, in just one more continent, surely can’t do any harm, right? One that won’t burn down with your house, but also isn’t just wafting vaguely in the Cloud at someone else’s whim. One that elevates your backup system from sensibly paranoid to borderline OCD. One, in this case, brought to you by rsync, find and Growl.

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I’ve been unhappy for a while having the SSH daemon on my web server VPSs with password authentication enabled. Of course, it’s on a non-standard port, blocks root logins, and takes a strong-ish password… but the risk of a successful dictionary attack has still felt too non-zero for comfort.

Equally, though, I’ve not wanted to give up the ability to log in to the servers from anywhere to fix things in an emergency, so I didn’t want to turn password authentication off and rely on public keys alone.

Until now, that is. I realised yesterday that, since I have iSSH on the iPhone, which does public key authentication, I can log into my servers from anywhere, even with password authentication turned off. Granted, doing anything serious on a tiny screen and slow connection is difficult. But all I actually need to be able to do from there is temporarily turn password authentication back on.

And to make this easy, I’ve put two ultra-simple scripts in ~/bin:

pwd_login_on.sh

#!/bin/bash
sudo sed -r -e 's/^PasswordAuthentication no$/PasswordAuthentication yes/' \
  -i.previous /etc/ssh/sshd_config
sudo /etc/init.d/ssh restart

pwd_login_off.sh

#!/bin/bash
sudo sed -r -e 's/^PasswordAuthentication yes$/PasswordAuthentication no/' \
  -i.previous /etc/ssh/sshd_config
sudo /etc/init.d/ssh restart

(These paths are suitable for Ubuntu 8.04).

Lovely.

Quick tip: you can get hold of some of Adobe’s very nice professional fonts for free when you download the InDesign CS4 trial (and possibly other CS4 apps too).

These include:

• Caslon Pro
• Chaparral Pro
• Garamond Pro
• Minion Pro
• Myriad Pro

If you don’t want to actually install InDesign, you can get to the fonts like so (if you’re a Mac user):

• Mount (double-click) the downloaded disk image
• Mount another disk image found on the newly mounted disk, at Adobe InDesign CS4/payloads/AdobeFontsAll/AdobeFontsAll.dmg
• The fonts are inside /Assets/contents on this second disk

Note that these fonts may well be covered by a very restrictive licence: I haven’t checked.

You might have noticed that Microsoft has lately started making available time-limited Virtual PC images of Windows installations with (separately) Internet Explorer versions 6, 7 and 8.

This is brilliant for Mac users who need to test websites in IE, because you get a real installation of each browser in its home environment, with the right JavaScript engine and working conditional comments, plug-ins, Windows Media Player, and so on. With the alternatives, such as running under Wine or using Multiple IEs in a single Windows virtual machine, one or more of these things tends to be missing.

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iWork and some other Mac apps provide the keyboard shortcut Apple-Alt-Shift-V for the extremely useful command Edit > Paste and match style. But Office 2008 provides no such equivalent for its equivalent command, Edit > Paste > Unformatted Text > OK. Annoying.

Happily, you can fix this with a strategically named and placed AppleScript. Open /Applications/AppleScript/Script Editor, and paste in the following lines:

tell application "Microsoft Word" 
  paste special (text object of selection) data type paste text
end tell

Save in /Users/YourUserName/Documents/Microsoft User Data/Word Script Menu Items as Paste unformatted\mosV.scpt (the backslashed bit at the end of the filename provides the shortcut). Restart Word and you can now paste without importing extraneous styles with Apple-Alt-Shift-V.

Update

You might also try this alternative approach (via a handy comment elsewhere):

try
  set theClip to Unicode text of (the clipboard as record)
  tell application "Microsoft Word" to tell selection to type text text theClip
end try

This has the advantage of leaving the cursor where you expect, at the end of the pasted text — the original script fragment leaves it at the beginning. And no, type text text is sadly not a typo: that’s really how Word likes to be addressed.

When creating a Firefox extension recently, I was surprised how much pain is involved simply in finding out, from within an extension, where that extension’s files are installed.

You have to create a ‘component’, which entails a fair chunk of unintelligible boilerplate code (well, unintelligible unless you’re much better acquainted with Firefox’s innards than developing a basic extension generally requires you to be).

Plenty of places will tell you roughly how to do it. But, after some experimentation, let me show you exactly how.

• Copy this JavaScript file into your extension’s /components directory (if that directory doesn’t exist yet, create it).
• Use it from elsewhere in your extension like so:

own_path = Components.classes["@mackerron.com/get_ext_dir;1"]
  .createInstance().wrappedJSObject.get_ext_dir();

And that’s it. Let me know if it helps you out.