Doctrine entities in Twig templates

In a Symfony2 project, Doctrine entities can be used inside Twig templates with the help of Twig extensions.

The example works with the standard Symfony2 installation and the AcmeDemoBundle, and it is supposed to add a set of links on one of the demo pages. Each link represents a color, while the HEX code for that color is displayed when the link is clicked. The colors are retrieved from the database.

The example is using Twig functions, but an alternative which is using global variables is also presented.

The Doctrine entity:

This entity has a basic structure which should store the name and HEX code for a color.

The Twig extension:

The following list contains the most important remarks related to the Twig extension:

  • The string returned by the “getName”  method – “color_extension” will be used to register the extension;
  • The “getColors” method is the one which returns the entities, using the EntityManager;
  • In order to have access to the EntityManager, the Twig extension needs to be registered by specifying that the EntityManager service (identified as “doctrine.orm.entity_manager”) will be passed as argument;
  • The key “get_colors” from the array returned by the “getFunctions” method is the actual Twig function name which needs to be called in the Twig template to return the entities.

Twig extension registration:

In order to register the Twig extension the following piece of code needs to be added to src/Acme/DemoBundle/Resources/config/services.xml:

As previously mentioned, the “color_extension” string is used in the service id and the EntityManager service is sent as parameter for the Twig extension.

Everything should be set by now, the only thing that needs to be done is to call the “get_colors” function inside a Twig template. Here’s an example:

The global variables alternative.

Update the Twig extension (src/Acme/DemoBundle/Twig/Extension/ColorExtension.php) with the following code:

This means that the “colors” key will become a global variable and can be used in a Twig template.

Easy file sharing with Python SimpleHTTPServer

An easy way to share files from your computer is to use Python SimpleHTTPServer. You don’t need to know Python programming to use the SimpleHTTPServer, the only requirement is to have Python installed on the machine where the files that needs to be shared are located.

Most Linux distributions are shipped with Python installed by default, but for Windows you might need to check how to use Python on Windows.

To start the SimpleHTTPServer “cd” into the directory which you want to be shared and run the command:

python -m SimpleHTTPServer 8000

You need to specify a port, usually 8000, like in the example should be just fine.
To access the shared files o to http://your_ip_address:8000.

Understanding file permissions and ownership on Linux

The files on a Linux system can have reading permissions, writing permissions, executing (running) permissions or no permissions for the user that owns that files, groups of users or the rest – users who does not own that files and they are not members of any group.

The usual file types are:

  • Directory – associated symbol d
  • Normal file – associated symbol (minus, dash)
  • Symbolic link (symlink) (like a shortcut on Windows) – associated symbol l

Permission types:

  • Reading – associated symbol r, or number 4
  • Writing – associated symbol w, or number 2
  • Executing (running) – associated symbol x, or number 1
  • No permission – associated symbol , or number 0

If a file has the reading permission you can open the file and read it, but you can not change the content. If a directory has the reading permission you can read the files in that directory, but you are not allowed to change their content.

If a file has the writing permission you can open the file for reading and for writing (you can change the file’s content and save it with the new content). You can not delete or rename a file unless the directory has the writing permission.

The execution permission allows the user to execute (run) the file (like a shell script).

User types:

  • User – the user name of the owner of the file or directory; if a user creates a file or directory it becomes the owner of that file of directory.
  • Group – a group of users (ftp, mysql), all group members have the same rights for the file or directory.
  • Other – all users that do not own the file or directory and they do not belong to any group that has right for the file or directory.

Setting permissions:

You can set the permissions using the chmod command. There two methods for changing file permissions:

  • Symbolic mode
  • Numeric mode

Symbolic mode

Setting the permissions is made using the associated symbols – rwx.

Actions are defined using mathematical symbols: the + (plus) symbol is used to add a permission, the – (minus) symbol is used to remove a permission, and the = (equal) symbol is used to remove the old permission and set a new one.

For the owners, associated symbols are u for user, g for group, o for others (the rest) and a for all.

To make a file executable type in a console:

chmod +x myfile

To remove the write permissions of the group:

chmod g-w myfile

Numeric mode

Instead of symbols, the associated number are used for setting permissions. The number for each owner will be the sum of the permissions for that owner.

To set the reading, writing and execution rights for the user you use the number 7 (4+2+1); to set the reading and writing rights for group will you use the number 6 (4+2); the reading permission for the rest (others) will be set using number 4.

The command for setting the permissions in numeric mode:

chmod 764 myfile

Here is the association between numbers and letters:

0  |  ---
1  |  --x
2  |  -w-
3  |  -wx
4  |  r--
5  |  r-x
6  |  rw-
7  |  rwx

Changing the owner:

It is done using the command chown.

To change the owner:

chown myusername myfile

To change the group and the owner:

chown mygroup:myowner myfile

To change only the group you use the command chgrp:

chgrp group myfile

Video tutorial

Check also a video tutorial about Unix File Permissions and Ownership (CHOWN, CHMOD, ETC) via


Enable trackball pulse notifications for HTC Hero with CM7

How to enable trackball pulse notifications for missed calls on HTC Hero with CyanogenMod 7 (or other CM7 based ROM like the one provided by elelinux).

Go to Settings -> CyanogenMod settings -> Interface  -> LED Notifications -> Unconfigured -> Missed Call -> Flash color

Select “White” and press back arrow.

Make a test using the “Flash test” option. If the trackball doesn’t work then you’re out of luck.

Save (using “Save” option) and go back.