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Copy files between a guest (virtualbox) and the host

I use VirtualBox and had a problem with copying files between my host (main computer on which you boot your computer) and the guests (virtual computer that you run on your host).

The fact is that it is all explained right here:

http://www.virtualbox.org/manual/ch04.html#sharedfolders

There are a few steps as follow.

Install the Virtual Box Tools

Install the Virtual Box Tools (called Guest Additions) on your guest; these tools allow your guest to communicate with the host to allow files to be written in a directory on the host.

To install those, it should be as easy as using the ...

Getting Ubuntu to playback DVDs

In order to playback a DVD you need to make use of commercial encryptions (also called codecs.) Actually Ubuntu calls them "non-free". The reality is these are patented and protected so people cannot just ripoff a DVD. Which is not true at all since pretty much any computer can play DVDs and thus can copy all the data. Anyway, because Ubuntu is by default for free software, it doesn't include all the necessary DVD stuff. This being said, they provide 100% of all the necessary code, pre-compiled and all you have to do is install it all with apt-get as follow.

(You must be root to ...

Compiling in 64bit with VC 2010 can result in a crashing software

Today, as I was trying to run a 64 bit application in Release mode under Windows 7, I got a crash about a NULL pointer. There is the debuggee (<- well known Microsoft spelling of Debugger) error window:

Unhandled exception in ... Access violation reading location 0x0000...

Unhandled exception at 0x52740ccf in guikeyboard_test_developer.exe:
0xC0000005: Access violation reading location 0x0000000000000000.

So... according to this error, the software access a NULL pointer. It took me some time, but the problem was not a NULL pointer, it was an unaligned memory access. In other words, it is trying to write a a pointer that is not 16 bytes aligned, which is ...

C printf(3) for int, long and long long that works every time

Of Note: This only applies to C99, not C++.

I learned something quite interesting today and wanted to keep a note of it.

Whenever I use a printf() with a format such as %ld and try to compile my code on "many" different platforms, I often get warnings on another one.

The fact is that an int, a long, a long long, an int32_t, int64_t all use a different combination depending on your platform and whether you're running in 32 or 64 bit.

So, the answer to this problem are the #define found in the inttypes.h header file:

PRId8
PRId16
PRId32
PRId64

These entries are used after

Deleting a database in Synergration

Synergration AccessBooksRT is a tool we use to get a copy of QuickBooks tables in an MS-Access database.

It works great for our purpose and transformed some super sluggish forms into lightning fast forms. We still use QODBC for some of the work (updates) but 99% now goes through the database generated by Synergration instead.

nice and ionice for Linux users

By default, a computer system gives each process the same priority level in regard to accessing your hard drive.

With newer versions of Linux, it is possible to use two other priorities: one where I/O is not primordial and thus you do not get it if anyone else wants it, and one where you want to work in realtime and have priority over anyone else.

This is achieved with the ionice command line (or corresponding kernel calls.)

This is particularly useful if you want to copy a partition to another and you know that it will take 20 minutes to copy everything... and thus the computer will be ...

SeaMonkey 2.0

I guess I liked Netscape just way too much... I used Mozilla after Netscape went down and bust, then I continued with SeaMonkey 1.x and now I just finished installing SeaMonkey 2.0.

There are features in this system that are just better than in FireFox. However, SeaMonkey 2.0 is a re-sync. with FireFox 3.x. In other words, this is very similar to FireFox, with the correct display features of the HTML code. But it keeps the menu, preferences and look in general of SeaMonkey. (although the fonts have changed... I'll have to get used to those!?)

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SVN and executables

One of the annoying thing with Subversion (SVN) is that at times it will add a execute flags to your files and there does not seem to be a function to easily remove that execute flag.

Doing a chmod on your file and trying an update, status or commit does not work. One way is to (1) copy your file, (2) delete the file from your SVN, (3) re-add the file after you carefully changeed the mode with a "chmod 644" or something similar. But of course, that means you lose your history...

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UPDATE using multiple tables

Today I wanted to copy a column from one table to another. One way is to go through the table and update the items one by one. The other way is to use the UPDATE order a copy the data as required.

The UPDATE command does NOT support such a feature by default and thus each database has its own syntax when it comes to how to make that work.

PostgreSQL uses an extra FROM between the SET and WHERE orders.

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