Let us have a look at the case of creating a command that will delete all items of a selected type (lots of people do face this job, as it is). I just want to be upfront and reveal it to you how the syntax of the command will look like: drush delete-content %content_type%, whereby %content_type% being the machine name assigned to the type of contact.
Drush-command staging is divided into three steps:
- example_drush.drush.inc file creation
- invocation of hook_drush_command() in the created file
- commands' description
example_module.drush.inc file creation
It is an instance of routine module creation: we start with creating example_drush.info and example_drush.module files. The module's main file may stay empty, it shoud exist, anyway, for the sake of the drush-command's correct functioning. Next, we get down to creating the batch file example_drush.drush.inc. It's ending should contain "drush.inc" so that the utility could recognize it as the one with drush-commands. Drush is looking up the batch files in the following foulders:
- /path/to/drush/commands foulder
- foulders enlisted in the "include" option
- system foulder for batch files drush. E.g., /usr/share/drush/commands
- ".drush" foulder in the user's home foulder
- sites/all/drush in the current installation of Drupal
- the included modules' foulders
hook_drush_command() invocation in the created file
The batch file's most important element is hook_drush_command(). It provides for the descriptions of the commands proper as well as the way they operate. The description resembles, in a way, the description of the elements in hook_menu. Let us investigate the key components of it:
- aliases - the list of contracted names of the commands. E.g., we can promptly substitute a long name for the command "pm-download" with a more concise "dl". Provided there are the synonyms supplied, the "long" command will keep functioning.
- callback - the name of the function which will be called in to perform the command. The function's name should contain (at its beginning) the relevant file's name. In our case we have example_drush_. The parameter is optional, so In case it were skipped, drush_invoke() will generate the name automatically.
- description - command's description.
- arguments - parameter array that's perceived of by the function. It's only utilyzed for the "drush help" command.
- required-arguments - is by default set up to FALSE. Once switched over to TRUE, the parameters will become obligatory.
- drupal dependenices - Drupal modules that should definitely be switched.
- drush dependencies - drush-files that are required for executing the command.
- bootstrap - the specified phase that Drupal has been bootstrapped to facilitate cooperation with the command.