docs/manual/developer/mod_example_1.c

/*
 * mod_example_1.c: Example module for Apache HTTP Server 2.4
 * A simple "Hello, world!" handler.
 */

#include "httpd.h"
#include "http_config.h"
#include "http_protocol.h"
#include "ap_config.h"

static int example_handler(request_rec *r)
{
    /* First off, we need to check if this is a call for the "example-handler" handler.
     * If it is, we accept it and do our things, if not, we simply return DECLINED,
     * and the server will try somewhere else.
     */
    if (!r->handler || strcmp(r->handler, "example-handler")) return (DECLINED);

    /* Now that we are handling this request, we'll write out "Hello, world!" to the client.
     * To do so, we must first set the appropriate content type, followed by our output.
     */
    ap_set_content_type(r, "text/html");
    ap_rprintf(r, "Hello, world!");

    /* Lastly, we must tell the server that we took care of this request and everything went fine.
     * We do so by simply returning the value OK to the server.
     */
    return OK;
}

static void register_hooks(apr_pool_t *pool)
{
    /* Create a hook in the request handler, so we get called when a request arrives */
    ap_hook_handler(example_handler, NULL, NULL, APR_HOOK_LAST);
}

AP_DECLARE_MODULE(example) =
{
    STANDARD20_MODULE_STUFF,
    NULL,
    NULL,
    NULL,
    NULL,
    NULL,
    register_hooks   /* Our hook registering function */
};