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A quick tip this, but a useful one. You can tail a log file in the background while running a script in the foreground. So for example, I frequently execute the following commands: 1. tail -f /var/log/httpd.log & /etc/init.d/apache restart 2. (The log file will spool onto the terminal as Apache is restarted.) 3. Once you are finished viewing the log file, foreground the log file process and kill it: fg Then terminate the foregrounded log tail with a control-c. ...

I am currently on holiday in Tenerife, and although I really like it here, one thing I do not like is the internet connection we have in our resort. Sometimes networked applications will just hang with no warning and there will be minutes where it’s not clear what is going on. Here are some ways you can find a little bit more about what is happening when an application is slow or seems to hang when you have a poor internet connection. Execute the following commands each in a separate terminal window. ...

Recently, myself and two colleagues from the BBC, ran a session on Test Driven Development at the Manchester University ‘Ultimate Programming’ society. The society is a gathering where students discuss cool things they have done with programming, and occasionally have guest speakers from industry. I found the society online and thought it would be great to get the BBC more involved in the local university happenings. It is the first outreach project that I have undertaken, and it required a lot of preparation. Our initial idea was to get students to implement the A* search algorithm in a practical session, using TDD. However after we had all implemented our own copy of the algorithm, and realised it had taken several hours each, we realised we’d not have enough time in the 2 hour slot that we had. ...

I needed to view a single frame of a m2v file that had been encoded by our designers for playing out on TV. The file name was .mpg but in actuality it was a single .m2v frame renamed to be a .mpg. Windows Media Player classic used to display the frame fine when I opened the file normally, under Windows XP. However now I have switched to a Mac, I have found that Quicktime and VLC refused to display the single frame. I couldn’t find a video player that would open the single frame. So I resorted to the command line version of ffmpeg, which I installed via macports, to convert this single frame to a jpg file to view as normal. This line worked a treat: ...

After I wrote a Java application in JDK 1.6, I was stuck for a while when I realised that the target deployment machine was Red Hat Enterprise Linux 4. RHEL4 does not support Java 1.6 in its default configuration. Luckily I found this article on the CentOS wiki which included instructions on how to install Java 1.6 on CentOS 4. Remembering that RHEL4 and CentOS 4 are almost identical, I tried the method supplied, and it worked. This is the page with the method: ...

Nagios can be seen as a automated test tool for systems, just as you would have automated tests for software projects. In test driven development (TDD), you write the tests first, and then use those tests to build up a software project that you can have confidence that it works. We can use this method to build up systems, or networks of systems. Plan out which services and processes should be running on your new systems, and then implement Nagios tests for every one. You can check the progress of your build by checking Nagios. I have been doing this at the BBC. It is a simple idea but one that seems to work.

I’m currently in the process of writing a web scraper for the forums on Gaia Online . Previously, I used to use Python to develop web scrapers, with the very handy Python library BeautifulSoup . Java has an equivalent called JSoup. Here I have written a class which is extended by each class in my project that wants to scrape HTML. This ‘Scraper’ class deals with the fetching of the HTML and converting it into a JSoup tree to be navigated and have the data picked out of. It advertises itself as a ‘web spider’ type of web agent and also adds a 0-7 second random wait before fetching the page to make sure it isn’t used to overload a web server. It also converts the entire page to ASCII, which may not be the best thing to do for multi-language web pages, but certainly has made the scraping of the English language site Gaia Online much easier. ...

At work, I still have to use Windows XP and Outlook 2003. I don’t particually mind this, except when I draft an email to someone and accidently I press Control-B instead of Control-V. Control-B will go ahead and send your partially composed email, resulting in some embarassment as you have to tell everyone to disregard it. So I wanted to remove the ‘send email’ shortcut keys in Outlook 2003. There are two ways of doing this, one involves editing your group policy, which is something only my IT administration team can do, and I didn’t want to have to involve them. The other way is by making a change to your registry, which I will describe here. ...

There is a problem I frequently encouter on Redhat/Fedora/CentOS systems with the output of the ls command. Under those distributions, the default setup is to display directories in a very dark colour. If you usually use a white foreground and a black background on your terminal client (such as Putty) then you will struggle to read the names of the directories under Redhat-based distributions. There are two soloutions that I have used: ...

I am moving to Manchester soon, and so I thought I’d get an idea of the housing market there by scraping all the Manchester Gumtree property adverts into a MySQL database. Once in the database, I could do things like find the average monthly price for a 2 bedroom flat in an area, and spot bargains through using standard deviation from the mean on the price through using simple SQL queries via phpMyAdmin . ...