Working with closed source products (Microsoft Visual Studio, .NET, ASP.NET, SQL Server, and Oracle) while at the same time experimenting with open source products (Eclipse, Java, MySql, and Spring) I am constantly baffled by the persistence of closed source developers and business people in their handling of second grade support, bad information, and lacking products.
Category Archives: Computers and Internet
Posts on computer science and the web, rants about OS:es, Window Managers, Platforms for almost publishing content on the web, and the like.
Badblocks
It took me some time to find out the equivalent of Window’s checkdisk/scandisk/chkdisk on Linux, but trust me, there are several.
For starters I am going to take a look at badblocks, a command that as the name implies, looks for bad blocks.
The basic format of badblocks are:
badblocks [options] device
If you have a fresh drive with no data or data that can be deleted on it you can do:
badblocks -s -w /dev/sdb
Note however, the -w command will erase all existing data on the drive so do not use it for drives with existing file systems on them. You cannot use -w on a mounted drive, unmount it first. The -s flag makes the command show a progress bar. This could come in handy when you are testing larger drives since even the fastest systems will take at least an hour to test an average sized drive (my 400GB took about 2 hours on a SATAII system).
If you want to test the drive without deleting data you can use the -n switch which will use non-destructive write-read mode, however, this switch can, for obvious reasons, not be combined with the -w switch.
badblocks -s -n /dev/sdb
Links:
DoNothing and numerical dyslexia
Small beauties in programming… and not all of them are made up either ;o)
DoNothing:
function DoNothing() {
Nothing();
}
Find one error:
private static final int TWENTYFOUR = 24;
private static final int THIRTYEIGHT = 32;
private static final int FOURTYTWO = 42;
The mystery of the magic file (or how i invented the .rte and .rtg file formats)
I’m just back from a head spinning experience of extreme Windowsism. A file that refused to be renamed, or deleted… until ten minutes later…
What happened was that I wanted to rename a file. Like I usually do, I clicked the file, then pressed F2, got the “editable” view of the file name and started typing.
Nothing happened.
I clicked around, trying to see if the computer was just slow or something like that. Well… the file explorer did not respond at all…
It was frozen. So I waited for it to unfreeze. Which it didn’t. It apparently had crashed.
I force-quitted. Restarted and retried. After all, perhaps it was just a fluke? Right?
Nope. Same exact problem.
I scratched my head, thought for a bit and rejected a number of alternative ways to go. I guessed it was time for the daily reboot… again today. And rebooted the system.
Once back in the catalogue (five minutes later) I found the same problem persisted. No rename, no file explorer, nothing but kill the program.
I was able to “solve” the problem however, by copying the file. Once I had it was in fact possible to rename the copy. All I had to do now was to remove the old file and, although kind of axy (as in trying to carve an inch high wooden statuette with an axe), the problem would be solved.
The file did not want to be deleted. However, the file explorer did not freeze this time so chalk one up for windows? Or not. Shutting down the file explorer and restarting it did not help either. It was time to harvest the vast experience of the firm.
I asked around in the office landscape trying to find someone that could help, and I got a number of helpful advice like “have you restarted the file explorer?” or “have you rebooted the machine?” All of which was rather not what I hadn’t already tried.
Finally someone suggested: “put two files in the same folder where the problematic file is placed, name them so they appear just above and just below the file with the problem, put something like ‘erase me’ at the end of them, wait a week and delete the file then.”
After having hyperventilated for a while to get the whole concept into my head and make it stick long enough to do what the guy had suggested I went ahead.
My magic file was named something like “My document 2.rtf” so after some experimenting with names that would place the file exactly where I wanted them I came up with:
My document 2.rte.delete.me.txt
My document 2.rtf
My document 2.rtg.delete.me.txt
Now for the mind blowing finale.
Once I had the files in place my folder looked like:
My document 2.rte.delete.me.txt
My document 2.rtg.delete.me.txt
The magic file had disappeared! Finally deleted!! Only about ten minutes after the button was pressed!!!
That was when I noticed the dialogue boxes saying “The file cannot be renamed, it has disappeared.” They were, in true windows style hidden under the file explorer window…
Aha, was my first thought, problem solved… Then I felt a chill going down my spine. Didn’t I try to rename before I deleted? Or did I try to delete first and rename later?
No! my mind screamed. I had a file, whose content was important but whose name was wrong. So deleting before renaming would be stupid. And renaming after I’d copied the file and renamed the copy would be equally stupid (not to mention impossible… there was already a file with that name…)
Somehow windows had confused the order of the operations?! BRRRRR!!!
You might think, hey he was working with a networked drive and the net was having some kind of problem or the order of the packages got confused. It’s a good idea, it could really happen, even though I think the Samba protocol (or whatever windows have chosen to call it) should be able to handle packages coming in haphazardly without getting confused like this, and the most probable result of Samba not managing that should be some kind of failure, even total failure demanding the drive to be remounted (or a blue screen or whatever XP uses when the OS-programmers run out of money, time or happiness).
Enough about networked drives… the drive in question was local! No network, no delays, not even cables (USB/FIREWIRE/eSATA or what have you)… unless you count the system bus. Does windows use TCP/IP on the system bus?
Well… thank God I have my important files on another OS altogether! Not to mention on RAID and USB backup…
Computers are scary… Windows computers are terrifying!
Iterating a list, and deleting from it, Java vs .NET
Or how I came to realize I could live a life time without .NET and be just as happy.
I’m just fresh from having tried to iterate a list… and delete items from it while iterating. In .NET with C#.
It turns out a statement like:
void deleteFromList(IList<X> list) {
foreach (X x in list) {
if (x.DeleteMe) {
list.Remove(x);
}
}
}
Will throw an InvalidOperationException stating you cannot perform a foreach and delete at the same time. This is actually not that big of a surprise, or it shouldn’t be… the same happens in Java if you delete and iterate at the same time.
This is how I would have done this in Java:
void deleteFromList(List<X> list) {
Iterator<X> itr = list.iterator();
while (itr.hasNext()) {
X x = itr.next();
if (x.DeleteMe) {
itr.remove();
}
}
}
It’s simple, clean and it does not throw exceptions. If you believe the code may be run asynchronously, slap on a “synchronized” and you’re home safe.
So, how to do this with .NET? Well, you can’t use Enumerators (which are the .NET “equivalent” of iterators), they don’t have a remove method. Further worse, if you are unlucky enough to run version 1.1 your only option seems to be some unholy concoction like:
void deleteFromList(IList<X> list) {
IList<X> toBeDeleted = new List<X>();
foreach (X x in list) {
if (x.DeleteMe) {
toBeDeleted.Add(x);
}
}
foreach (X x in toBeDeleted) {
list.Remove(x);
}
}
Don’t even start a conversation on synchronization with this mixup. Anyway, those who are “lucky” enough to code .NET 2.0 can do something like:
myList.RemoveAll(delegate(X x) { return x.DeleteMe; });
Now, if you’d like to base the “DeleteMe” calculation on some external paramter like input to the deleteFromList method or if you’d like to do more than just delete x you’ll have to experiment, it’s probably possible… with a solution like the double lists above perhaps?
Regardless. Someone said it was old news to be a Java programmer, I can only guess because of the lower hour wastage when you program Java systems, which in turn means lower bills to the clients and finally lower wages to the programmers.
It costs to be on top…
Moblock traffic blocker
Moblock (moblock-deb) is a so called traffic blocker. It prevents connections from certain IP numbers (defined in block lists) to gain access to your computer. The whole purpose is that the blocked IP numbers usually belongs to this or that organization that wishes to find out more about your Internet habits and other information they have no reason to get their noses into.
Moblock has a big brother called Peerguardian by Phoenixlabs but development on this program seems to have been discontinued, and unfortunately at a stage where the program doesn’t work (at least for me it doesn’t). I am also sure there are some Windows variants of an IP-blocker (I’m guessing Bluetack is the right place to go).
Installing Moblock on Ubuntu turns out to be a very simple affair. Mainly do two things: Add moblock’s repository to your repository list, and run an apt-get command. (Here’s an even better instruction for installing Moblock on Ubuntu).
The installation takes care of setting up cron-jobs to update your block lists every day, installs moblock as a service started every time the machine is started, and makes the first download, after which the program (or in fact, demon) is started and you are safe.
The above link is a very good instruction on installing moblock, and it even have instructions on how to perform some simple troubleshooting.
If you run linux I suggest you take a look at moblock’s home page, or you can check out it’s project page on sourceforge.
GoogleBot may crash .NET 2.0 sites
ASP.NET 2.0 apparently has a vulnerability when doing URL rewriting, making it possible for Googlebot (and possibly other search engine bots as well?) to crash a .NET 2.0 site.
BasKet Note Pads – note-taking application
BasKet is a very nice application I just stumbled across. It is a kind of OneNote for Linux. In Ubuntu (probably Debian and others as well) it can be managed as a regular package.
I’m using it mostly when writing and ordering ideas and the like, but I can see myself doing much more with it…. once I’ve made sure it’s stable enough. Let me get back on that with a more proper review later.
How to add a body on load function with Javascript
This is an article on how to add a javascript function that will be run when a web page has loaded. We begin by defining a function for running after a page (or actually window) has been loaded:
function bodyOnLoad() {
..
..
}
And then we’ll do:
window.onload = bodyOnLoad;
However, we also want to make sure our setting of the load event doesn’t remove some other setting. This is done by also keeping any older events.
We store the previous on load event by doing;
var prevOnLoad = window.onload;
And we redefine our bodyOnLoad function:
function bodyOnLoad() {
prevOnLoad();
..
..
}
However, we can make the creation of the function and the setting of the event a little bit more effective by doing:
window.onload = function() {
prevOnLoad();
..
..
}
You still need to get prevOnLoad before you do that
This becomes even more obvious once we create a function for adding new load events:
function addLoadEvent(func) {
var prevOnLoad = window.onload;
window.onload = function() {
prevOnLoad();
func();
}
}
In this way, we can concentrate on creating the new load event outside of the function for adding it to the window.onload.
function myEvent(){
..
..
}
addLoadEvent(myEvent);
We might even do:
addLoadEvent(
function (){
..
..
}
);
Notice the difference between curly braces “{}” and parenthesis “()”
Finally, we have to make sure there is a load event set for the window before calling it from the new event, so we need to check for this:
function addLoadEvent(func) {
var prevOnLoad = window.onload;
if (typeof prevOnLoad != 'function') {
window.onload = func;
}
else {
window.onload = function() {
prevOnLoad();
func();
}
}
}
Programming humor
In case you wondered. Sure, programming can be humorous, but this is more about looking at programming with humor. Or, well, I’ve found a few funny things I’d like to share… XML is like violence: if it doesn’t solve your problem, you’re not using enough of it.
People who make buttumptions about their censoring settings, will be embarbutted when they repeat this clbuttic mistake.
Talkwards 