Category Archives: Computing

Hardware, software, computer science and the rest

Traffic Jam in the Lounge

When I tried to read my e-mail from the lounge this morning it didn’t work because our MacBook Pro couldn’t connect to our wireless network. I went upstairs to check the access point which was working fine. After I reentered the password the wireless connection started to work again.

Because I was still wondering what went wrong I started iStumbler my favourite wireless network monitoring tool for Mac OS X. Within seconds I knew what caused the problem: three other access point in the neighbourhood were broadcasting on the same channel as ours. I had checked the wireless channels when we moved in. But because the wireless reception of our old PowerBook G4 is not very good it didn’t pick up any of the other networks. I decided to reconfigure the access point to use a free channel. Picking the new channel was somewhat difficult because there were two further wireless networks nearby which used different channels.

But it seems that I didn’t do a bad job because my wireless network is working stable again. I wonder how long that will last. One of the owners of other access points which are still fighting over a single channel could also change the configuration. I considered to buy an 802.11n capable access point and use the 5 GHz band as a long term solution. But I realized hat our Nintendo Wii doesn’t support 802.11n unfortunately. So I hope for the best until I get stuck in the next traffic jam in the lounge.

WordPress 2.0.11 vs. MySQL 5.0.51

Over the last few days the posts in this Blog were displayed in the wrong order. As a result an article from 2006 appeared on the front page. This was apparently caused by a incompatibility between version 2.0.11 of the blogging software WordPress and version 5.0.51 of the MySQL database which I installed recently.

Because I couldn’t find the incorrect SQL statement which caused the problem I decided to upgrade WordPress. And the good news is that that version 2.3.1 fixed the problem.

The “ps” conspiracy

The first decent UNIX systems I worked with were the good old Sun 3 and Sun 4 systems of the computer science department of the University Paderborn. At that time all the machines were running SunOS 4.0 which was derived from BSD 4.2. And of course it supported the proper syntax of the ps command e.g. ps -guwx. And that is what I got used to.

When the University started deploying Solaris 2.x I was really annoyed that ps now expected System V style options. But I found /usr/ucb/ps which supported all the options I knew. All was well.

But the System V nonsense didn’t stop there unfortunately. Linux was the next victim (or offender?). ps started complaining about bad syntax at some point. This could however be fixed by setting the enviroment variable PS_PERSONALITY to bsd. I made the necessary changes to my account’s configuration and all was well.

I was however really shocked when I found out that Mac OS X Leopard had joined the conspiracy. Its ps command doesn’t accept BSD options anymore and expects System V style options instead. I personally find that highly annoying especially considering that Mac OS X is a BSD derivative.

But there is a bit of hope for BSD fans like me: if you omit the hyphen in front of the options Leopard’s ps command still accepts BSD style options. So I wrote a little script called ps which behaves like Mac OS X Tiger’s ps command. And all is well.