Drupal Tip: List a node’s taxonomy terms inside a Block

George Notaras — Thu, 07 May 2009 01:38:48 +0000

It’s been several months since the last time I had done any coding on Drupal. Although many people might find it trivial, here is a PHP snippet to enter in a custom block, so that the taxonomy terms of the currently displayed node are printed as an unordered list inside that block. Also, each list item will be a link pointing to the relevant term page.

First of all, in order to be able to include PHP code, which will be evaluated, inside your posts, it is required to activate the PHP Filter module. Double check at admin/settings/filters that only trusted roles can use the PHP filter, otherwise your web site could be at risk. By default, only the administrator can use this filter.

To create the custom block, go to admin/build/block/add and enter a description and a title for your custom block. Paste the following code on the body textarea:


/**
 * Prints an unordered list of the terms (as links) that are
 * associated to the currently displayed node.
 */
if ( arg(0) == 'node' && is_numeric(arg(1)) ) {
    $node = node_load(arg(1));
    if (module_exists('taxonomy')) {
        $terms = taxonomy_link('taxonomy terms', $node);
        print theme('links', $terms, array('class' => 'node-terms'));
    } else {
        print 'No associated categories.';
    }
}
?>

Make sure you select the PHP filter from the list of the input filters. Also, set the rest of the settings according to your needs and save the custom block.

Your new block should be available in the block list in admin/build/block and you should be able to use it straight away.

Now to some technical details about arg(0) and arg(1), which probably seem a bit cryptic to a user that is not experienced with Drupal (like me). Assume we have the following URL to a node: www.example.org/node/23, which means that the path to the page is /node/23. Well, arg(0) is the node part and arg(1) is the second part; 23 that is. Read about the arg() function.

This should explain the following part of the snippet above:

if ( arg(0) == 'node' && is_numeric(arg(1)) ) {
    $node = node_load(arg(1));
[...]
}

I give some emphasis on this as it is a snippet you will use quite often in order to use any of the node object’s properties inside a block.

Drupal Tip: List a node’s taxonomy terms inside a Block, unless otherwise expressly stated, is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 Unported License. Terms and conditions beyond the scope of this license may be available at www.g-loaded.eu.

Use the Alternatives System to switch to a custom Firefox release

George Notaras — Wed, 18 Jun 2008 05:46:25 +0000

From a user’s perspective, having to use an old beta version of Firefox in my primary desktop, while, at the same time, a final stable release of the browser has been released, is a bit annoying. But, the fact that this happens due to technical issues makes it partially acceptable. The following article aims to provide step-by-step instructions about how to use the alternatives system to set a custom Firefox release, downloaded from mozilla.org, to be the system’s default. Using this method the user is relieved from having to go through all the firefox launchers and menu entries in order to edit the paths to the firefox executable. Moreover, this post should also be a good example of how to use the alternatives system in the Linux distributions that support it.

Update: Firefox 3.0 final has become available from the official fedora updates repository. It seems that the technical issues of the past do not exist any more! Kudos! This tutorial will still give you an idea though about how to quickly and easily switch between the default and custom versions of the same software in your system.

Fedora 9 has been used as the desktop system for this article. The provided information will certainly work in CentOS and RHEL, but might also work for other linux distributions which use the alternatives system, such as Debian, Ubuntu, OpenSUSE etc. As far as I know, Gentoo and its derivatives use their own system.

In order to check if “alternatives” is available in your system, try one of the following commands:

which alternatives
which update-alternatives

Firefox Installation

First of all, we install a precompiled (binary) Firefox distribution, downloaded from mozilla.org, in the /opt directory. All the following commands should be issued by ‘root‘ or by your regular user using ‘sudo‘.

Change to the /opt directory, download and extract the firefox package:

cd /opt/
wget ftp://ftp.mozilla.org/pub/firefox/releases/3.0/linux-i686/en-US/firefox-3.0.tar.bz2
tar -xjf firefox-3.0.tar.bz2

Now change to the /opt/firefox/ directory, delete the plugins/ subdirectory and create a symlink to the system’s directory containing the firefox plugins (/usr/lib/mozilla/plugins/ in Fedora).

cd firefox/
rm -fr plugins
ln -s /usr/lib/mozilla/plugins/ plugins

The installation of the custom Firefox version is complete.

Set the system-wide default Firefox version

In this section we will use the alternatives system in order to provide us with two options:

Use Fedora’s default Firefox release. This means that /usr/bin/firefox should be executed whenever we issue the ‘firefox‘ command.
Set our custom Firefox release as the system’s default. This means that /opt/firefox/firefox should be executed whenever we issue the ‘firefox‘ command.

Note: Describing the details of the alternatives system is out of the scope of this article, so it is highly recommended that you study the alternatives manual page (man 8 alternatives)

In the following steps we will add a group, named “firefox“, of alternative options for the location of the firefox executable. These options are actually filesystem locations which will be linked by the /usr/local/bin/firefox symlink. Note that we use the /usr/local/bin/… path for our symlink, because /usr/bin/firefox is occupied by fedora’s firefox executable. The latter will not be called directly any more, as the executables located in /usr/local/bin/ override the ones located in /usr/bin/, so whenever the command ‘firefox‘ is invoked, /usr/local/bin/firefox will actually be used. The latter is a symlink, which links to either fedora’s firefox executable or our custom firefox executable.

So, we add the ‘firefox‘ group of options:

/usr/sbin/alternatives --install /usr/local/bin/firefox firefox /usr/bin/firefox 10
/usr/sbin/alternatives --install /usr/local/bin/firefox firefox /opt/firefox/firefox 20

Now we can manually set which firefox executable to use as the system’s default. In other words, the following command links /usr/local/bin/firefox to the desired executable (/opt/firefox/firefox in our case):

/usr/sbin/alternatives --set firefox /opt/firefox/firefox

Instead of the --set option as shown above, we can use the –config option, so that a list of the available alternatives is displayed and we are prompted to make a selection:

# /usr/sbin/alternatives --config firefox
There are 2 programs which provide 'firefox'.
  Selection    Command
-----------------------------------------------
   1           /usr/bin/firefox
*+ 2           /opt/firefox/firefox
Enter to keep the current selection[+], or type selection number: 2

Finally, we can issue the following command to get an overview of our current configuration for the group ‘firefox‘:

# /usr/sbin/alternatives --display firefox
firefox - status is manual.
 link currently points to /opt/firefox/firefox
/usr/bin/firefox - priority 10
/opt/firefox/firefox - priority 20
Current `best' version is /opt/firefox/firefox.

Revert to the original state

If for any reason you need to revert things back to the default state, all you have to do in order to remove all the “alternatives” we had configured in the previous section is the following:

/usr/sbin/alternatives --remove firefox /opt/firefox/firefox
/usr/sbin/alternatives --remove firefox /usr/bin/firefox

No other configuration is required. From now on, whenever the ‘firefox‘ command is invoked, fedora’s old /usr/bin/firefox is executed.

Final Thoughts

Technical issues in the linux distribution preparation process might limit the user to certain software versions. The alternatives system provides users with the choice to configure the system in a way that it is extremely easy to switch between default and custom versions of the same software.

Use the Alternatives System to switch to a custom Firefox release, unless otherwise expressly stated, is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 Unported License. Terms and conditions beyond the scope of this license may be available at www.g-loaded.eu.

G-Loaded Journal » Customization