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CURLOPT_TRAILERFUNCTION(3) curl_easy_setopt options CURLOPT_TRAILERFUNCTION(3)

NAME
       CURLOPT_TRAILERFUNCTION - Set callback for sending trailing headers

SYNOPSIS
       #include	<curl.h>

       int curl_trailer_callback(struct	curl_slist ** list, void *userdata);

       CURLcode	   curl_easy_setopt(CURL   *handle,   CURLOPT_TRAILERFUNCTION,
       curl_trailer_callback *func);

DESCRIPTION
       Pass a pointer to a callback function.

       This callback function will be called once right	before sending the fi-
       nal  CR LF in an	HTTP chunked transfer to fill a	list of	trailing head-
       ers to be sent before finishing the HTTP	transfer.

       You can set the userdata	argument with the CURLOPT_TRAILERDATA option.

       The trailing headers included in	the linked list	must not be  CRLF-ter-
       minated,	 because  libcurl  will	 add  the appropriate line termination
       characters after	each header item.

       If you use curl_slist_append to add trailing headers to the  curl_slist
       then  libcurl  will duplicate the strings, and will free	the curl_slist
       and the duplicates once the trailers have been sent.

       If one of the trailing headers is not formatted correctly (i.e. Header-
       Name:  headerdata) it will be ignored and an info message will be emit-
       ted.

       The return value	can either  be	CURL_TRAILERFUNC_OK  or	 CURL_TRAILER-
       FUNC_ABORT which	would respectively instruct libcurl to either continue
       with sending the	trailers or to abort the request.

       If you set this option to NULL, then the	 transfer  proceeds  as	 usual
       without any interruptions.

DEFAULT
       NULL

PROTOCOLS
       HTTP

EXAMPLE
       #include	<curl/curl.h>

       static int trailer_cb(struct curl_slist **tr, void *data) {
	 /* libcurl will free the list */
	 tr   =	  curl_slist_append(*tr,  "My-super-awesome-trailer:  trailer-
       stuff");
	 return	CURL_TRAILERFUNC_OK; }

       CURL *curl = curl_easy_init(); if(curl) {
	 /* Set	the URL	of the request */
	 curl_easy_setopt(curl,	CURLOPT_URL, "http://example.com/");
	 /* Now	set it as a put	*/
	 curl_easy_setopt(curl,	CURLOPT_PUT, 1L);

	 /* Assuming we	have a function	that will return the data to be	pushed
	    Let	that function be read_cb */
	 curl_easy_setopt(curl,	CURLOPT_READFUNCTION, read_cb);

	 struct	curl_slist *headers = NULL;
	 headers  =  curl_slist_append(headers,	  "Trailer:   My-super-awsome-
       trailer");
	 res = curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers);

	 /* Set	the trailers filling callback */
	 curl_easy_setopt(curl,	CURLOPT_TRAILERFUNCTION, trailer_cb);

	 /* Perform the	request, res will get the return code */
	 res = curl_easy_perform(curl);

	 curl_easy_cleanup(curl);

	 curl_slist_free_all(headers); }

AVAILABILITY
       This  option was	added in curl 7.64.0 and is present if HTTP support is
       enabled

SEE ALSO
       CURLOPT_TRAILERDATA(3),

libcurl	7.72.0		       October 31, 2019	    CURLOPT_TRAILERFUNCTION(3)

NAME | SYNOPSIS | DESCRIPTION | DEFAULT | PROTOCOLS | EXAMPLE | AVAILABILITY | SEE ALSO

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