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From "Pranesh Vadhirajan" <>
Subject Some fundamental questions about output filters
Date Fri, 13 Jan 2012 19:10:51 GMT

I've been trying to use output filters in my code in order to read the
response that is being sent from Apache to a web client.  


I believe this would be a proper use for an output filter, please correct me
if I'm wrong.  I am attempting to read the content of the response from
within a certain module, and I would like to know how to access the contents
of the output filter etc.  


I've been looking into how output filters work, but I'm not sure I
understand the concept.  


So here are my basic questions on how to write that code:


Can I register my output filter within the registration hooks of my module
code?  For example I did the following and I am getting various errors, and
I am wondering if there's a proper way to do it.  The goal is to be able to
access the contents of the response from within my module and to print it to
my error log (or anywhere else), but I am not sure how to do this. : 


static apr_status_t apcontent_filter_in(ap_filter_t *f, apr_bucket_brigade
*b, ap_input_mode_t mode, apr_size_t *readbytes)


    const char *str;

    int length;

    apr_bucket *e;


        ap_get_brigade(f->next, b, mode, APR_BLOCK_READ,1);


        e = APR_BRIGADE_FIRST(b);


        if (e->type == NULL) {

                return APR_SUCCESS;



        apr_bucket_read(e, &str, &length, 1);

        fprintf(stderr,"req body: %s\n",str);


    return APR_SUCCESS;



static int my_handler(request_rec* r) {


        int is_ip = 0, fqdn_id, ap_id, nid_sl = 0, nid_fl = 0;

        char time_buffer[30]; 

        char* remote_address;

        char* cookie;

        char* session_id = NULL;


        apr_bucket_brigade* request_body_brigade;

        ap_filter_t *f;

        apr_size_t readbytes=(apr_size_t)r->sent_bodyct;



        return DECLINED;




static void my_register_hooks (apr_pool_t *p) {

        ap_hook_handler(my_handler, NULL, NULL, APR_HOOK_MIDDLE);

apcontent_filter_in,NULL, AP_FTYPE_RESOURCE) ;



module AP_MODULE_DECLARE_DATA my_module = 



        NULL,                                           /* Per-Directory
Configuration */

        NULL,                                           /* Directory Config
Merger */

        NULL,                                           /* Per-Server
Configuration */

        NULL,                                           /* Server Config
Merger */

        NULL,                                           /* Command Table
(Directives) */

        my_register_hooks     /* Registering Hooks */



If this is not the proper way to read from an output filter could someone
please explain the proper way?


Pranesh Vadhirajan



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