Ellks

Montag, 19. Oktober 2015

ArchLinux - Maude

Download the latest version of maude:
http://maude.cs.illinois.edu/w/index.php?title=Maude_download_and_installation
Export the *.zip by typing unzip ~/Downloads/Maude*
Go into the exported directory.
Run the file maude.linux64

Troubleshooting:

Programm does not start and does not find libtinfo.so.5. Note we're referencing a lib which might has a similar name. Show yourself all similar libs with ls /lib64 | grep libncurs.
cd /lib64
sudo ln -s libncursesw.so.6.0 libtinfo.so.5

Mittwoch, 7. Oktober 2015

From Java to C# - A few notes

You might instantiate a generic class like a normal array:
List<T> mylist = new List<T>() { t1, t2, t3, ..., tn};
LINQ - Language Integrated Query

Queries for different DBs, XML, Generics

Properties

These are easy written accessors
Futhermore an easy possiblity to convert information

e.g. we store seconds in our time class
you might write a property which allows you to simulate an other variable, like hours
which still relays on the seconds.
public string Name { get { return ...; } set { ... = value;} }

Only functions noted with the keyword virtual might be overwritten.
Override is a keyword, not an annotation
Javas super is C#s base
You must to append an f to your float

float f = 3.141f

There is a special keyword var

var is a type which is determined at compile-time. So it can't change on run-time!
var v = (new List<int>() {1,2,3})[0];

v has the type int now

You might use var in foreach

foreach (Type t in Collection) is javas for (T t : Collection)
All types are objects!

There are two subtypes:

Valuetypes
Referencetypes

There is not multiple inheritance.
You implement interfaces and super classes in the same way:

class sub : super { // ... }
class implementation : interface { // ... }

There a different types of lambdas:

Action<T1, ..., Tn>(...) which maps on void
Func<T1, ..., Tn, Tresult>(...) which maps on given type Tresult

Futhermore there are two keywords for easy threading:

await
async

Dienstag, 6. Oktober 2015

Edit Markdown with vim like a king!

When i did start writing Markdown files, it was for my projects on github. After editing on githubs webpage, i was using vim at local repositories.

After a short time, i figured out that chromium has a Markdown interpreter. It's called MarkDown Preview Plus. I installed it because of the following features:

It can read local files.
On the fly refresh - When you edit your markdown file and store it, the interpreter upgrades the view automatically.

After i installed the file, i was wondering if i couldn't bind chromium to a vim hotkey.

So i added this line to my .vimrc:
autocmd BufEnter *.md exe 'noremap <F5> :! chromium %:p<CR>'

This line binds the key F5, on files ending with .md to chromium. So, when you press F5 chromium opens and the Markdown Preview Plus interprets the file.

Dienstag, 15. September 2015

C# - Mono with MySql Connector under Linux

I assume you already installed the mono runtime.
Your logged in on your Linux machine.
You did open a terminal.

Download the .NET/mono assembly, provided by oracle.com.
http://lmgtfy.com/?q=c%23+mysql+connector
Unzip the files.
Enter the v2.0 folder.
Open a terminal.
I'm not sure what the different versions are. When you know it, fell free to leave a comment.
Now you add the "MySql.Data.dll" assembly to the runtime assemblies.
sudo gacutils -i MySql.Data.dll

That's it usually. Well, i had some permission trouble. You might go to the directory /urs/lib/mono/gac/MySql.Data/ and look in the subfolder for your added assembly MySql.Data.dll. Here you might type ls -l to show your permission on the file. Type chmod +rx MySql.Data.dll. With this you granted yourself and all other users of your computer the permission to read the file and execute it.

Make sure to add the references System and System.Data to your project.

Freitag, 28. August 2015

Running tasks in command background

When you're connected to a server via. ssh, you might have trouble running processes asynchronous. Following i wan't to show a few commands, which allow you to pause a process, move it to background, continue the process in back or foreground and let it even continue, when the shell closes.

All commands listed below:

jobs - shows all current processes.
bg %jobid - continue job in background.
fg %jobid - bring background process into foreground.
ctrl+z - in terminal shown as ^Z; pauses current process and moves it to background.
disown %jobid - removes the process from table of active processes.

First of all i show you how to start a process in background. It runs until it needs input from command line. To do so, you might type cp extremelargefile ../ &.

[1] + suspended (tty input) cp extremelargefile ../ &.

When the process suspended and you wan't to continue it in foreground, on terminal, you might type fg %jobid. To figure out the jobid you might type jobs. All current gets listed then.

A process is running, e.g. cp. There might be a situation that you copy a large file and forgot to add & to the command. So you're running the process in foreground. To suspend the process and bring it to background you might press ctrl+z. When you wan't the process to ran further, type bg %jobid. As already told, you can bring this process back to the front by typing fg %jobid.

For example:

> cp extremelargefile ../
^Z
zsh: suspended  cp extermelargefile ../
> jobs
[1]  - suspended (tty output)  cp extremelargefile ../
> bg %1
[1]  - continued (tty output)  cp extremelargefile ../
> fg %1
[1]  + continued (tty output)  cp extremelargefile ../

Donnerstag, 27. August 2015

Block websites with /etc/hosts

What's /etc/hosts for?
Every UNIX-like OS has a file for resolving hostnames to IP. You can block specific hostnames by directing them to your localhost IP, which is 127.0.0.1. Usually i block a few sites i visit regulary, which are distracting me to study. In following an example is listed.

# Address       Hostname
127.0.0.1       localhost
127.0.0.1       localhost.localdomain
255.255.255.255 broadcasthost
::1             localhost
127.0.0.1       local

127.0.0.1       9gag.com
127.0.0.1       facebook.com
127.0.0.1       facebook.de

The first line, beginning with the hashtag is a comment.

What about windows?
In windows 7 there was a similar file under C:\\system32\drivers\etc\hosts. There should be a similar file, in newer Microsoft operating systems. http://bfy.tw/1Vce

HAW Hamburg VPN under Linux

Since CISCOs AnyConnect VPN doesn't support Linux, we need to use an open source implementation. I suggest to use openconnect.

Under Arch Linux you might download it via. pacman -S openconnect. After you downloaded it, you might connect with sudo openconnect <address>;. The programm will ask you for your A-Label and your password. These are the same credentials you use for your helios and e-mail access on haw-mailer.haw-hamburg.de/owa.

Here is an example how it looks like:

sudo openconnect connect.haw-hamburg.de
[sudo] password for user: 
POST https://connect.haw-hamburg.de/
Attempting to connect to server 141.22.5.20:443
SSL negotiation with connect.haw-hamburg.de
Connected to HTTPS on connect.haw-hamburg.de
XML POST enabled
Please enter your username and password.
Username:a-label
Password:
POST https://connect.haw-hamburg.de/
Got CONNECT response: HTTP:/1.1 200 OK
CSTP connected. DPD 30, Keepalive 20
Connected tun0 as 141.22.197.180, using SSL
Established DTLS connection (using GnuTLS).

Useful Links: