Available Languages: en. In the second part of this document, which deals with configuration directive and context awareness, we will be looking at a module that simply writes out its own configuration to the client.
First and foremost, you are expected to have a basic knowledge of how the How to write apache modules programming language works. In most cases, we will try to be as pedagogical as possible and link to documents describing the functions used in the examples, but there are also many cases where it is necessary how to write apache modules either just assume that "it works" or do some digging yourself into what the hows and hoq of various function professional movie review writer site online. Lastly, you will need to have a basic understanding of how modules are loaded and configured in the Apache HTTP Server, as well as how to get the headers for Apache if you do not have them already, as these are needed for compiling new modules.
To compile the source code we are building in this document, we how to write apache modules be using APXS. Every module starts wrlte the same declaration, or name tag if you will, that defines a module as a separate entity within Apache :. The name of the module is used primarily for two things:.
For now, we're only concerned with the first purpose of the module name, which comes how to write apache modules play when we need to load the module:.
Within this name tag of ours is also a bunch of references to how we would like to good essay for college things: Which directives do hoe respond to in a configuration file how to write apache modules. We'll return to all these elements later in this document.
A hook is essentially a message telling the server that you are willing to either serve or at least take a glance at certain requests given by clients. Furthermore, in the end, it is writw to the user of the server how and when each module will come into place.
Thus, the server itself does not presume to know which module is responsible for handling a yow request, and will ask how to write apache modules module whether they have an interest in a given request or not.
Two of these are AddHandler and SetHandler. Let's take a look at an example using AddHandler. In our example case, we want every request ending with. What this modulew the server is the following: Chandlers thesis we receive a request for a URI ending in.
Thus, when a request is being served that ends in. To begin with, we only want to create a simple handler that replies to the client browser when a specific URL is requested, so we won't bother setting up configuration handlers and professional cv proofreading websites au how to write apache modules yet.
Our initial module definition will look like this:. This lets the server know that we are not interested in anything fancy, we just how to write apache modules to hook onto the requests and possibly handle some of them. In this example module, the function has just one mpdules To create a simple hook that gets called after all the rewrites, access control etc has been handled.
Thus, we will let the server know that we want to hook into its process as one of the last modules:. We will discuss how to create a handler in the next chapter.
Hooking into the request handling phase is but one of many hooks that you can create. Some other ways of hooking are:. A handler is essentially a function that receives a callback when a request to the server is made.
It is passed a record of the current request how it was made, which headers and requests were passed along, who's giving the request and so onand is put in charge modulds either telling the how to write apache modules that it's not interested in the request or handle the request with the tools provided. The functions used in this example will be explained later in the how to write apache modules "Some useful functions you should know".
The most essential part of any request is the request record. This struct, typically just referred to as r in modules, contains all the information you need for your module to fully process any HTTP request and respond accordingly.
Apache relies on return values from handlers to signify whether a request was handled or not, and if so, whether the request went well or not. If it monthly homework sheet pre k handling a request, it should either return the now value OKor a specific How to write apache modules status code, for example:.
The server may still have other handlers that are interested in this request, for instance the logging modules which, upon a successful request, will write down a summary of what was requested and how it went.
To do a full stop and prevent any further processing after your module is done, you can return the value DONE to let the server know that it should cease all activity on this request and carry on with the next, without informing other handlers.
General response codes:. In essence, each server, connection and request have their own memory pool that gets cleaned up when apzche scope ends, e. How to write apache modules your module needs to do is latch onto this memory pool, how to write apache modules you won't have to worry about having to clean up after yourself - pretty neat, huh?]