111 lines
3.7 KiB
Groff
111 lines
3.7 KiB
Groff
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.\" **************************************************************************
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.\" * _ _ ____ _
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.\" * Project ___| | | | _ \| |
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.\" * / __| | | | |_) | |
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.\" * | (__| |_| | _ <| |___
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.\" * \___|\___/|_| \_\_____|
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.\" *
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.\" * Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
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.\" *
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.\" * This software is licensed as described in the file COPYING, which
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.\" * you should have received as part of this distribution. The terms
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.\" * are also available at https://curl.se/docs/copyright.html.
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.\" *
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.\" * You may opt to use, copy, modify, merge, publish, distribute and/or sell
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.\" * copies of the Software, and permit persons to whom the Software is
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.\" * furnished to do so, under the terms of the COPYING file.
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.\" *
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.\" * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
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.\" * KIND, either express or implied.
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.\" *
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.\" * SPDX-License-Identifier: curl
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.\" *
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.\" **************************************************************************
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.\"
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.TH CURLOPT_TRAILERFUNCTION 3 "14 Aug 2018" libcurl libcurl
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.SH NAME
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CURLOPT_TRAILERFUNCTION \- callback for sending trailing headers
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.SH SYNOPSIS
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.nf
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#include <curl.h>
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int curl_trailer_callback(struct curl_slist ** list, void *userdata);
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CURLcode curl_easy_setopt(CURL *handle, CURLOPT_TRAILERFUNCTION,
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curl_trailer_callback *func);
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.fi
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.SH DESCRIPTION
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Pass a pointer to a callback function.
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This callback function is called once right before sending the final CR LF in
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an HTTP chunked transfer to fill a list of trailing headers to be sent before
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finishing the HTTP transfer.
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You can set the userdata argument with the \fICURLOPT_TRAILERDATA(3)\fP
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option.
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The trailing headers included in the linked list must not be CRLF-terminated,
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because libcurl adds the appropriate line termination characters after each
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header item.
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If you use curl_slist_append to add trailing headers to the curl_slist then
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libcurl duplicates the strings, and frees the curl_slist and the duplicates
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once the trailers have been sent.
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If one of the trailing header fields is not formatted correctly it is ignored
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and an info message is emitted.
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The return value can either be \fBCURL_TRAILERFUNC_OK\fP or
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\fBCURL_TRAILERFUNC_ABORT\fP which would respectively instruct libcurl to
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either continue with sending the trailers or to abort the request.
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If you set this option to NULL, then the transfer proceeds as usual
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without any interruptions.
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.SH DEFAULT
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NULL
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.SH PROTOCOLS
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HTTP
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.SH EXAMPLE
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#include <curl/curl.h>
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static int trailer_cb(struct curl_slist **tr, void *data)
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{
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/* libcurl frees the list */
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*tr = curl_slist_append(*tr, "My-super-awesome-trailer: trailer-stuff");
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return CURL_TRAILERFUNC_OK;
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}
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CURL *curl = curl_easy_init();
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if(curl) {
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/* Set the URL of the request */
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curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/");
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/* Now set it as a put */
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curl_easy_setopt(curl, CURLOPT_PUT, 1L);
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/* Assuming we have a function that returns the data to be pushed
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Let that function be read_cb */
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curl_easy_setopt(curl, CURLOPT_READFUNCTION, read_cb);
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struct curl_slist *headers = NULL;
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headers = curl_slist_append(headers, "Trailer: My-super-awesome-trailer");
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res = curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers);
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/* Set the trailers filling callback */
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curl_easy_setopt(curl, CURLOPT_TRAILERFUNCTION, trailer_cb);
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/* Perform the transfer */
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res = curl_easy_perform(curl);
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curl_easy_cleanup(curl);
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curl_slist_free_all(headers);
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}
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.SH AVAILABILITY
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This option was added in curl 7.64.0 and is present if HTTP support is enabled
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.SH RETURN VALUE
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Returns CURLE_OK.
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.SH "SEE ALSO"
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.BR CURLOPT_TRAILERDATA (3),
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.BR CURLOPT_WRITEFUNCTION (3)
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