However, for FuncNet we have a simple script running in a cron job, which posts a status message to @FuncNet every so often. This runs without any supervision, so I was left scratching my head as to how I could obtain the access token and access token secret required to post. The app registration page at http://twitter.com/oauth_clients/details/NNNNNN for each app only shows its consumer key and consumer secret which are something different.

Eventually, thanks to Net::Twitter developer Marc Mims on this thread, I discovered that there’s a whole separate page for each app at http://dev.twitter.com/apps/NNNNNN/my_token which has the access token and access token secret required for the app to post to its own account.

Once you have these, you can post like this (thanks again to Marc for example):

    use Net::Twitter;
 
    my $nt = Net::Twitter->new(
        traits => [qw/OAuth API::REST/],
        consumer_key        => $YOUR_CONSUMER_KEY,
        consumer_secret     => $YOUR_CONSUMER_SECRET,
        access_token        => $YOUR_ACCESS_TOKEN,
        access_token_secret => $YOUR_ACCESS_SECRET,
    );
 
    $nt->update("Bob's your uncle!");

Why you need 4 distinct incomprehensible strings in order to post a single tweet, I don’t know, but presumably it’s justified on security grounds. What isn’t justified is Twitter hiding two of them somewhere else entirely, and not linking to that place from the main OAuth page for the app.

Not useful, guys.

N.B. In the URLs above, NNNNNN corresponds to the numeric ID for your application. If you don’t know what this is, just go to http://dev.twitter.com/apps, click on the app name to get the consumer strings, and then click on My Access Token to get the access strings.

Thankfully, the solution was easier than I thought. Do all the following as root…

1. Install dpkg, the Debian package management tool:

yum install dpkg

2. Download the base package for your architecture, and the gnome support package, from here:

http://repository.spotify.com/pool/non-free/s/spotify/

3. Create a temp directory, and unpack them there (we want to check for clashes):

mkdir spotify
cd spotify
dpkg -x ../spotify-client-qt_0.4.7.132.g9df34c0-1_amd64.deb .
dpkg -x ../spotify-client-gnome-support_0.4.7.132.g9df34c0-1_all.deb .

4. This gives you a directory tree starting at /usr. You can check for clashes like this:

find -not -type d -exec ls -l /'{}' \;

… and make sure there’s no files found.

5. Then re-extract them into your root partition (hence checking for clashes first):

dpkg -x ../spotify-client-qt_0.4.7.132.g9df34c0-1_amd64.deb /
dpkg -x ../spotify-client-gnome-support_0.4.7.132.g9df34c0-1_all.deb /

6. Finally, we need to manually install qt-x11 as this dependency is needed:

yum install qt-x11

7. Then just type spotify and log in!

Seems pretty stable so far, apart from a couple of minor glitches.

EDIT: As suggested by Tyson Key in this thread, I got rid of the audio glitches by starting the PulseAudio volume control (/usr/bin/pavucontrol) before Spotify. Maybe this adds some buffering or something.

N.B. I take no responsibility if this process damages your computer, your music collection, your hearing or your sanity. Try at your own risk

Say I am working outside the office firewall, on a machine called home, and I need to get into a MySQL server inside it. (Doesn’t have to be MySQL, but just for argument’s sake.)

There’s a machine called gateway I can ssh to and tunnel through, but for security reasons, the database server mysql doesn’t accept connections from gateway directly. But my desktop machine at the office (err… desktop) can connect to mysql.

One way round it is to ssh from home to gateway and forward a port on gateway to the ssh server on desktop:

home $ ssh -L 2222:desktop.example.org:22 -tAY gateway.example.org

And then in another terminal, ssh from home to desktop via this tunnel, forwarding another port on home to the incoming connections port on mysql (3306 in MySQL’s case usually):

home $ ssh -p 2222 -L 23306:mysql.example.org:3306 127.0.0.1

This time, you’re connecting to home port 2222, but because of the first command, this forwards you straight to desktop port 22.

Now both tunnels are in place, you can just connect to port 23306 on home and arrive by magic at mysql. In another terminal (or from your MySQL GUI):

home $ mysql -uUSER -pPASS -h127.0.0.1 -P23306

This example shows a tunnel-within-a-tunnel. There should be a way to make this work using end-to-end tunnelling instead, I tried but didn’t get anywhere. But that might be due to ssh server restrictions on our equivalent of gateway.

If none of this means anything, there’s an intro to ssh port forwarding here.

They’ve finally (after nearly six years) added the ability to temporarily turn the code formatter off for a tricksy block that needs its own custom formatting. e.g.:

			// @formatter:off
			xml
			.append( "<node id='" )
			.append( protein )
			.append( "'><data key='class'>" )
			.append( cls )
			.append( "</data><data key='label'>" )
			.append( protein )
			.append( "</data></node>" );
			// @formatter:on

See the Off/On Tags tab for details.

Nice one guys… Eventually.

#!/bin/bash
export MYSQL_PWD=myrootpassword
BACKUP_DIR=/mnt/backups/mysql_backups
DATE=`date -I`
for dbname in `mysql -uroot --batch --skip-column-names -e "show databases;" | grep -v information_schema`; do
	/usr/local/bin/mysqldump -u root $dbname | gzip -9 > $BACKUP_DIR/$dbname-$DATE.sql.gz
done
 
# Clear backups older than 7 days
/usr/local/bin/find $BACKUP_DIR/*.sql.gz -mtime +7 -delete

Edited to include compression. Remember to include full paths if you’re running it from a crontab, just in case.

Chris Staite from the University of Birmingham has built a statically-linked version of Chromium, the open source version of Google’s Chrome browser, for Centos.

You can get it from here.

I was getting so sick of Firefox’s slowness and bloat, and Chromium is so much snappier, and more memory-efficient too.

Although to be fair, I don’t have nearly so many extensions installed yet…

It should just work out of the box with no extra dependencies to install. I’m using 64-bit Centos 5.4, and although it’s a 32-bit app, it seems entirely happy so far.

I have two network interfaces in my Ubuntu guest (on OS X 10.4 host), one NAT, one host-only.

Sometimes one of them doesn’t get an IP address — in ifconfig it has an inet6 address but not an inet address.

Today I tried

sudo dhclient eth1

and it worked — all it needed to do was re-query VirtualBox’s built-in DHCP server.

I would have thought this would do that automatically:

sudo /etc/init.d/networking restart

However that didn’t help… But dhclient did.

Another recurring problem is that when I move between different networks, DNS resolution gets screwed up. There’s a description of this with a suggested work around (using VBox’s DNS Proxy) here:

http://forums.virtualbox.org/viewtopic.php?f=1&t=28332

However, while this seemed to help with two of the networks I use frequently, it didn’t with a third, even after rebooting.

So, as suggested on one or two threads, I’ve removed the DNSProxy setting, and set the Ubuntu guest to use Google’s public DNS servers instead of those provided by the DHCP server for the NATted virtual NIC. (Blah blah blah.) Follow example here (more or less):

http://grumpymole.posterous.com/how-to-use-google-public-dns-or-opendns-in-ub

Seems to be working so far… But only tested on one of the offending networks, and without rebooting yet. Updates to come later.

… Nope, after upgrading to Snow Leopard and the latest VirtualBox (it’s now from Oracle — scary), random problems persist.

Sometimes I’ll lose guest-host connectivity in the middle of a session, without any sleep or other interruptions, but will still be able to see the internet from the NAT adaptor.

One possible solution here involving using OS X itself as the NAT router:

http://akutz.wordpress.com/2009/08/20/building-a-better-os-x-firewall-or-how-i-solved-the-nat-problem-for-virtualbox/

… but it’ll take work.

Or maybe a simpler version of the same approach: have a single host-only adaptor, use OS X’s internet sharing to share the AirPort card, and manually tell the vbox to use 192.168.56.1 as the default gateway:

http://forum.virtualbox.org/viewtopic.php?f=1&t=26544

If all else fails, try using a different ethernet hardware emulator.

I have a Maven project, call it frontend-war, which contains the main service code for FuncNet. A unit test kept failing in Eclipse with NoSuchMethodError, one of my least favourite screw-ups to disentangle.

In this case it was particularly frustrating, as the method (on a class in one of the main project’s dependent jars, called service-utils) definitely existed, was public, and had the right signature. Also, even more weirdly, when I ran the tests in Maven from the command line, they passed.

Cue all the usual Eclipse cargo-cult dead-chicken-waving — cleaning everything, closing and reopening projects, etc. etc. No joy.

Then it hit me… (solution below the jump)

One of the other jars included by frontend-war, called sessionDB, also included service-utils — and was using an out-of-date version. This version didn’t include the method I was calling (at least not with that signature). The dependency hierarchy looked something like:

frontend-war-CURRENT
    service-utils-1.2.9
        …
    sessionDB-1.3.3
        service-utils-1.2.4
        …

So I rebuilt sessionDB against the latest version of service-utils, then rebuilt frontend-war against that, and it worked.

So, my fault for getting myself into jar hell, although even if you don’t bring it on yourself, it’s hard to avoid it if you use a lot of open-source components, and Maven — which I still argue is a timesaver overall — tends to exacerbate it. Take a look at the Dependency Graph view in Eclipse’s POM Editor sometime — if you see any red arrows, that means two or more different versions of a dependency are being requested by different modules within your project.

So why did it work on the command line and not in Eclipse? To be honest, I don’t know in detail. But in cases like this, the classloader will (AFAIK) just pull in whichever version is requested first, so Eclipse’s classpath management must have happened to process the dependencies in a different order from Maven’s — meaning it worked by pure luck.

Note: My solution — updating sessionDB to use the latest service-utils — wasn’t a problem, because all three of the modules in the unholy ménage à trois belonged to me. But what do you do if two third-party libraries request different versions of the same jar?

A famous notorious example of this tends to happen with Hibernate, which depends on a really out-of-date version of ASM — or at least it used to, I haven’t checked recently. Lots of open-source projects use ASM but more recent versions clash nastily with the old one Hibernate requires.

The solution in this case is to use Maven’s exclusions clause to specifically exclude ASM from Hibernate’s transitive dependencies. Thankfully it can just use the more recent versions without problems.

But what would you do if one of the libraries you were using depended on a method that was no longer available in a more recent jar? Then you’re really in jar hell. Answers on a postcard…

So I’ve replaced my iTunes Dock icon with a little AppleScript that checks whether said disk is mounted first:

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tell application "Finder"
	if exists (disk "LaCie") then
		tell application "iTunes" to activate
	else
		display dialog "Don't start iTunes without LaCie external disk mounted." buttons {"OK"} default button 1 with title "Cannot start iTunes" with icon stop
	end if
end tell

Compile, save as script, add to dock, bingo. (Obviously, replace LaCie with the name of your external HD, as it appears in /Volumes when mounted.)

For extra points, you can give it iTunes’ icon too. Just get Info on iTunes and select the little icon in the top left (not the big one under Preview). Then just cmd-c, select the same icon in the script’s info window, and cmd-v.

This is fine in native desktop apps, but less fine in some text-mode programs (e.g. vim), when for some reason this often produces a superscript ³ instead.

So I’ve set up a custom keyboard mapping in iTerm to map F3 to #, which works nicely. However!

If I’m SSHed in to a remote Linux machine (or even my local Ubuntu VirtualBox) neither of these keys work in X apps. But, xmodmap (via the config file ~/.Xmodmap) can help. For some reason, Macs all have a dedicated key for these characters — § and ± — which no-one ever uses. But with this line in ~/.Xmodmap we can remap it to produce #:

keycode 18=numbersign

UPDATE: I’ve found a better way which works pretty much globally…

Using Ukelele you can copy the British keyboard layout and then remap keys to your heart’s content. I’ve moved the § character to the alt-§ key combination, in case I ever need it, and moved the # character to the raw § key. This seems to be respected almost everywhere so I don’t need to mess around with alt-3 or F3 any more. Joy. It also works over JollysFastVNC to a remote RealVNC server, which none of the other methods did.

Unfortunately, things still aren’t perfect. If I actually open a VirtualBox console session into GNOME on the local Ubuntu VM, the pointless § and ± key actually produces < and > so neither of these tricks work. In fact, I can’t get anything to generate a # even though I have the MacBook Pro Intl keyboard layout selected in GNOME. Any ideas?

UPDATE 2: YES!! I’ve finally cracked it for VirtualBox. With the help of the xkeycaps command, I discovered that X the keycodes coming into Ubuntu weren’t what I thought they were — somewhere the Mac-ness of the keyboard layout was getting lost. It turned out that the § key was generating keycode 94 instead. So I set up this in .Xmodmap on the Ubuntu VM:

keycode 94=numbersign

Now it works in VirtualBox too. Leave gifts of thanks below