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  Understand diff in Unix

diff is an important tool program in Unix. It is used to compare differences of two files, it is the foundation for code version control. If you type : $ diff <file_before_change> <file_after_change> diff will tell you what's the difference between these two files. The result may not be so easy to understand, so now I will show you how to understand diff. 1. 3 formats of diff diff has 3 formats due to historic reasons. normal diff context diff unified diff 2. Demo files For easy d...

   diff,Unix,version control,git     2012-09-03 10:49:36

  Access control in Java -- doPrivileged

Previously we have introduced how Java performs permission check to protect resource access. What if sometimes we need to give some class the temporary access to some resource which it initially doesn't have? AccessController provides six doPrivileged methods to fulfill this requirement. These six methods have below signatures : static T doPrivileged(PrivilegedAction action)static T doPrivileged(PrivilegedAction action, AccessControlContext context)static T doPrivileged(PrivilegedExceptionA...

   JAVA,SECURITY,DOPRIVILEGED     2016-03-08 05:46:42

  CSS DIV position analysis

When using CSS to set the position of DIV, we may often get confused with the 4 position properties : static, relative, absolute and fixed. If we don't understand them correctly, we may often get unexpected result. Here we make some analysis to them.The definitions of these 4 properties:static : The default position property. It has no position actually. The element will appear where it should be (top, bottom, left, right or z-index has no use here)relative : This one will position relati...

   CSS, DIV,position,relative,absolute     2013-01-29 03:23:57

  How does Base64 work

Base64 is a data encoding scheme used in safe data transfer such as HTTP and its extensions. Base64 encoding can conver arbitrary group of bytes into a sequence of readable ASCII characters. These converted characters can safely put in a HTTP header without causing any problem while the peers process the HTTP header. Base64 encoding was invented as part of the MIME content transfer encoding. It is similar to other encoding schemes such as Uuencode and BinHex but with higher efficiency....

   ALGORITHM,BASE64     2016-03-09 23:47:40

  Apple unveils iPad Mini

Apple unveiled iPad family's new product -- iPad Mini, it means that Apple gets into 7 inch tablet PC market now formally. iPad mini, has a 1024*768 resolution 7.9-inch screen, It has the same resolution as iPad 2. As a low-end product of iPad family, iPad mini still retains the front and rear camera, a dual-core A5 processor, battery life time is 10 hours. Apple said that the iPad mini battery is the thinnest and biggest in iPad family. Previously the media said the smallest storage space of iP...

   iPad mini,Price     2012-10-23 15:10:41

  Sorry, I don't want to download your fucking app

You should not claim yourself as a mobile Internet service provider if your product doesn't have an App nowadays. The topic cannot get away from App when we talk on bus, restaurant. Recently it becomes a little bit quiet, but the app wind does not seem to stop, it seems every website may have an App. According to data released by Apple a couple of days ago, its application store app downloads already exceeded 50 billion. However some people are not happy with this.Some people created a blog ...

   App,Update,Force download     2013-05-19 02:50:02

  Some famous product release venues

About product release conference, you must remember Apple Worldwide Developers Conference(WWDC), right? But do you remember where the conference is held? Actually, when companies release new products, they will hold some kind of conferences or sessions to introduce their products. But does anyone know what are the places where these conferences are held? Here geekpark summarized some product release places for us. 1. Moscone West Convention Center Moscone West Convention Center is the biggest co...

   Conference, Place,Product release     2012-10-11 20:32:22

  Create animated refresh button in Android

In Android, we can have drawings on a button, also we can put animated drawings on a button as well. Today we will show how to create an animated refresh button with an animated spinner on it. We need to create an animated drawing first. Here we name it as progress.xml and put it in the res/drawable folder: <?xml version="1.0" encoding="utf-8"?><animation-list xmlns:android="http://schemas.android.com/apk/res/android"    android:id="@+id/spin_refresh" android:oneshot="fal...

   Animation,Spinner,Refresh button,Android     2012-11-02 11:51:41

  A C++ program puzzle

Recently I came across a question asked by wang2191195 on a Chinese IT forum CSDN which asks about a C++ program puzzle. He has a code snippet which cannot be compiled. The code is:#include <cstdlib> #include <iostream> using namespace std; class Base{ public: virtual void func(){ cout << "Base::func()" << endl; } virtual int func( int num ){ cout << "Base::func( int " << num << " )" << endl; return 0; ...

   C++,Puzzle,Hide,Overload     2012-05-13 02:31:26

  The war with spam comment

Spam comments are annoying and notorious. They are either malicious data from hackers to exploit the loopholes of the site or advertisements posted by robots. These kinds of comments have their own features and patterns, if we are careful enough, we can find ways to block most of them although it's not so easy. To block the comment with malicious executable codes such as JavaScript, we should remember one rule : never trust user input. So wherever there are user inputs, we need to check the vali...

   Spam comment,Block,Filter     2013-11-29 20:29:43

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