mysql auto backup

First create a shell script which is used to backup database, here we named the script as mysql_backup.sh:

In above command, we use date command to generate current date, and use it as part of filename.

After that we need to make this file executable

 

To make this backup script run automatically, we should create a cronjob. Type following command to open cronjob editor

crontab -e

Write following text and save it

Above command means the cronjob will run at 0:00 everyday

 

 

Check MySQL case-insensitive query or table name

I tried to install Umbrao CMS, it supports MySQL database but it need MySQL to support case-insensitive query and table name.

 

Following is way to check whether case-insensitive query is supported:

show variables where variable_name=’lower_case_table_names’;

or check lower_case_table_names option in my.ini (MySQL configuration file)

 

If this option’s value is set to 1, then case-insensitive query and table name is supported.

QWebEngine crash with exception code 0×80000003

QWebEngine is a new web browser engine introduced in Qt 5.4, it’s used to replace the old QWebView. QWebView is based on WebKit, while QWebEngine is based on Chromium browser, so it’s faster and supports more features.

I wrote a very simple program to test QWebEngine, following is the code:

Compiling and running is smooth. But when I tried to run this demo on another machine, it crashed, and an error dialog is shown with the message “An unknown software exception (0×80000003) has occurred at 0x023c5b7e. Click OK to terminate the program.

By chekcing the log file (debug.log) I found some helpful information:

[ERROR:icu_util.cc(154)] Couldn’t mmap D:\Qt\Qt5.4.0\5.4\msvc2013_64\icudtl.dat
[FATAL:content_main_runner.cc(719)] Check failed: base::i18n::InitializeICU()

We can see the icudtl.dat path is not correct, because it doesn’t exist at all.

To fix it we need to create a new file named “qt.conf” under the application directory, and fill it with following content:

 

(This bug is posted at https://bugreports.qt.io/browse/QTBUG-42083)

WebServlet cannot be resolved to a type

WebServlet annotation is introduced in Servlet 3.0, it’s used to simplify the servlet creation (we don’t need to define it and its URL mapping in web.xml)

The WebServlet annotation usage is

e.g.

Then the user can visit /servlet/GetMailFileOwner to access this servlet

 

But today I met a problem with using WebServlet annotation. First I added WebServlet on the Linux machine (Eclipse Luna), and switched to another Windows machine (MyEclipse), then I tried to rebuild the project, I got following error:

On the Windows machine, I use the default servlet.jar which is added when I create the new Dynamic Web Project. But I replaced the default servlet.jar file with Tomcat 8.0 libraries.

So the solution is to add Tomcat 8.0 libraries to Java Build Path (We need first download Tomcat 8.0 and set it up for Eclipse, otherwise Eclipse will not find this Tomcat 8.0 libraries)

HTML set checkbox as readonly

Sometimes we don’t want to make some form fields non-editable to users, like Product ID, Order Created Date, Post Author, etc.

For HTML text input and textarea controls, we can add “readonly” attribute to disallow users to modify their value, but this attribute will not work for checkbox control. So how should we disable the checkbox (or set it as readonly)? The “disabled” attribute will do the job

(It works for both radio box and checkbox)

 

You will see following checkbox and radio button is disabled:


Fabric.js set text color

Fabric.js is a powerful javascript canvas library which wraps html5 canvas operation, and introduces objects (text, shape, path, etc.) to developer.

There is a common method set() for object, it can be used to set property of an object. But if you want to change text color, text.set(‘color’, ‘#0f0′) will not work.

To set color of text, we need modify the fill attribute or use setColor() method (only available for text object)

Or

 

 

The URL is not accessible when installing Magento

When installing Magento, we may get such error “The URL is not accessible”.

In some earlier versions of Magento, we can fix this problem by change code of app/code/core/Mage/Install/Model/Installer/Config.php
Just change

to

Will solve the problem. It’s because that the URL rewriting doesn’t work for some reasons. (Magento uses .htaccess files to add URL rewriting rules)

 

But in Magento 1.9, checking the “Skip the base url validation” option will solve this problem

Set sorting layer in unity c#

Sorting layer is a property of SpriteRenderer, it’s used to specify which object is at top, and which object is at bottom.

If you want to change the sorting layer in script, you can use following code:

 

 

Access PHP built-in web server from other devices

We often use following command to start the PHP built-in web server.

php -S localhost:port

But in this way only the machine which starts the server can access it, any other computers cannot access it.
To solve this problem, we can use 0.0.0.0 as the binding IP address

php -S 0.0.0.0:8000

Then other devices are able to access our server as well. Using 0.0.0.0 as the IP addres will make the server bind all available IP addresses on the machine.

No module named Crypto.PublicKey

When I tried to import the “paramiko” module, I got following error:

No module named Crypto.PublicKey

That means we need to install pycrypto library. Run following command to install pycrypto library by using pip:

In the installation I got a different error message:

error: Unable to find vcvarsall.bat

That means we need a C compiler to compile this extension. But we can also download a pre-built extension for windows: http://www.voidspace.org.uk/python/modules.shtml#pycrypto

 

After installing this extension and tried to import “paramiko” module, I got the error “No module named Crypto.PublicKey” again. We should rename “crypto” directory under “Lib/site-packages” to “Crypto”, then importing paramiko will work.