Drush for Developers - Second Edition: Effectively manage Drupal projects using Drush

Drush works on Unix-like operating systems (such as Ubuntu and OSX) and Windows operating systems.

If you use Windows, consider using something like VirtualBox (https://www.virtualbox.org) to install a virtual machine that runs, for example, Ubuntu (http://www.ubuntu.com). If you still want to use Drush on Windows, there is an installer available at http://www.drush.org/drush_windows_installer. Note, however, that the installer installs an older version of Drush, so some of the contents of this book won't work.

Let's start by making sure that you have PHP 5.3.0 or greater installed. To do so, open a terminal and run the following command:

$ php -v

The output should look something like the following code screenshot:

As you can see, I am using PHP 5.5.9. If you get a Command not found message or your version is lower than 5.3.0, you will need to install or upgrade PHP. Refer to your vendor documentation to do this as the steps will vary.

On Linux and OSX platforms, the recommended way to install Drush is through Composer (https://getcomposer.org), a dependency manager that has become the standard in the PHP world. Installing Composer can be accomplished with the following commands:

$ cd $HOME
$ curl -sS https://getcomposer.org/installer | php
$ sudo mv composer.phar /usr/local/bin/composer

If you find any issues while running the preceding commands or while installing it through a packaging system such as homebrew, then take a look at the official installation instructions for Composer (https://getcomposer.org/doc/00-intro.md#globally-on-osx-via-homebrew). Once you have completed the installation, you can verify that it works by running the following command:

$ composer about 
Composer - Package Management for PHP 
Composer is a dependency manager tracking local dependencies of your projects and libraries. 
See http://getcomposer.org/ for more information. 

At the time of writing this book, the latest available version of Drush is 7.0.0-alpha5 (https://github.com/drush-ops/drush/releases/tag/7.0.0-alpha5). This is the version that we will use. The Drush core team does a fantastic job of keeping backwards compatibility between major versions, so if you have already installed a more recent version of Drush, you should be okay as practically all the examples in the book will work.

Let's go ahead and install Drush. Once Composer has been installed (see the previous section on installing Composer), you can install Drush with the following command:

$ composer global require drush/drush:7.0.0-alpha5 -v
Changed current directory to /home/juampy/.composer
./composer.json has been updated
Loading composer repositories with package information
Updating dependencies (including require-dev)
    - Installing drush/drush (7.0.0-alpha5)
    Downloading: 100%         
    Extracting archive
drush/drush suggests installing youngj/httpserver
Writing lock file
Generating autoload files

The preceding command has downloaded Drush 7.0.0-alpha5 into $HOME/.composer/vendor/bin/drush. In order to use Drush from anywhere in the system, we need to make sure that Composer's bin directory is present at our $PATH environment variable. We can do so with the following commands:

$ sed -i '1i export PATH="$HOME/.composer/vendor/bin:$PATH"' \
   $HOME/.bashrc
$ source $HOME/.bashrc

Note the use of $HOME and $PATH, which are environment variables. $HOME contains the location of your home directory, while $PATH represents a list of directories to look for executable files. You can view the contents of these variables by executing echo $HOME or echo $PATH. Take a look at your home directory to check whether there is .bash_profile, .bash_login, or .profile file at $HOME. If you find them, adjust the preceding commands, so the $PATH variable is adjusted in these files as well.

Finally, we can test that Drush has been installed successfully and contains the right version:

$ cd $HOME
$ drush --version
 Drush Version   :  7.0.0-alpha5

If you prefer to install Drush manually, then follow these steps:

The main README file at the Drush repository has a great section on POST-INSTALL tasks (https://github.com/drush-ops/drush#post-install) with additional information on configuring PHP and extra settings for environments such as MAMP. It's worth taking a look at it.

Let's start with a very simple command such as core-status, which prints environment information about Drush and, if available, a Drupal site. Assuming that we have a Drupal project installed at /home/juampy/projects/drupal, let's run this command here and see its output:

$ drush core-status
 Drupal version                  :  7.29-dev                        
 Site URI                        :  http://default                  
 Database driver                 :  mysql                           
 Database username               :  root                            
 Database name                   :  drupal7x                        
 Database                        :  Connected                       
 Drupal bootstrap                :  Successful                      
 Drupal user                     :                                  
 Default theme                   :  bartik                          
 Administration theme            :  seven                           
 PHP executable                  :  /usr/bin/php                    
 PHP configuration               :  /etc/php5/cli/php.ini           
 PHP OS                          :  Linux                           
 Drush version                   :  7.0.0-alpha5                    
 Drush temp directory            :  /tmp                            
 Drush alias files               :                                  
 Drupal root                     :  /home/juampy/projects/drupal    
 Site path                       :  sites/default                   
 File directory path             :  sites/default/files             
 Temporary file directory path   :  /tmp                

The preceding output informs us about the main configuration of the Drupal project plus some Drush environment settings.

The core-status command accepts a single argument that specifies which setting is to be retrieved (you can see this information by running drush help core-status). An argument is a string of text that acts as an input data for a command. Arguments are entered after the command name and are separated by spaces. Therefore, if we need to print just the items containing version in the setting name, we can execute the following command:

$ drush core-status version
 Drupal version   :  7.29-dev     
 Drush version    :  7.0.0-alpha5 

Drush commands might accept zero to any number of arguments depending on their nature. Beware that some commands expect arguments to be given in a certain order. For example, the variable-set command, used to change Drupal environment variables, requires the first argument to be the variable name and the second argument to be the variable's new value. Hence, the following example sets the site-name variable to the My awesome site value:

$ drush variable-set site-name "My awesome site"
site-name was set to "My awesome site".        [success]

Drush commands might accept options through the command line, which alter their default behavior. Options are in the form of --option-name or --option-name=value. Additionally, some options have a shorter version. For example, you can accept all confirmations for a Drush command by appending --yes or its shorter version: -y.

Let's take a look at options with an example. The core-status command has an option to show the database password. We will now add it to the command and inspect the output:

$ cd /home/juampy/projects/drupal
$ drush core-status --show-passwords database
 Database driver     :  mysql     
 Database username   :  root      
 Database password   :  mysecretpw          
 Database name       :  drupal7x  
 Database            :  Connected 

The --show-passwords option orders the core-status command that we want to see the database password of the Drupal site being bootstrapped.

Excluding some exceptions, there is no strict ordering for options and arguments when you run a command. Besides, Drush does a great job parsing arguments and options no matter how we mix them up in the input. However, our commands will be more readable if we follow this pattern:

$ drush [global options] [command name] [command options] [arguments]

Here is an example:

$ drush --verbose core-status --show-passwords database 

And the following are the commands used in the previous example:

Besides the fact of higher clarity by using the preceding structure, there are some commands in Drush that require options to be given in this order. This is the case of the core-sync Drush command, which is a wrapper of the actual Unix rsync command used to copy files and directories. Let's take a look at the following example:

$ drush rsync @self:%files/ /tmp/files --dry-run
You will destroy data from /tmp/files and replace with data from /home/juampy/projects/drupal/sites/default/files/
Do you really want to continue? (y/n):

The preceding command copies files recursively from a Drupal project into /tmp/files. The --dry-run option is an rsync specific option that attempts to copy files but does not make any actual changes. Now, let's try to run the same command but this time placing the option before the command name:

$ drush --dry-run rsync @self:%files/ /tmp/files
Unknown option: --dry-run.  See `drush help core-rsync` for available options. To suppress this error, add the option –strict=0.  [error]

We can see in the preceding output that Drush attempted to evaluate the --dry-run option and failed as it did not recognize it. This example demonstrates that you should carefully read the description of a command by running drush help command-name in order to understand its options, arguments, and ordering.

Most of Drush commands support a shorter name to be used when invoking them. You can find them in parenthesis next to each command name when running drush help, or in the Aliases section when viewing the full help of a command.

For example, the core-status command can also be executed with status or just st, which means that the following commands will return identical results:

$ drush core-status
$ drush status
$ drush st