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12a2ed970f
In every libcurl option man page there are now 8 mandatory sections that must use the right name in the correct order and test 1173 verifies this. Only 14 man pages needed adjustments. The sections and the order is as follows: - NAME - SYNOPSIS - DESCRIPTION - PROTOCOLS - EXAMPLE - AVAILABILITY - RETURN VALUE - SEE ALSO Reviewed-by: Daniel Gustafsson Closes #7656
116 lines
4.4 KiB
Groff
116 lines
4.4 KiB
Groff
.\" **************************************************************************
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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) 1998 - 2021, 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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.\" **************************************************************************
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.\"
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.TH CURLOPT_WRITEFUNCTION 3 "16 Jun 2014" "libcurl 7.37.0" "curl_easy_setopt options"
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.SH NAME
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CURLOPT_WRITEFUNCTION \- set callback for writing received data
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.SH SYNOPSIS
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.nf
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#include <curl/curl.h>
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size_t write_callback(char *ptr, size_t size, size_t nmemb, void *userdata);
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CURLcode curl_easy_setopt(CURL *handle, CURLOPT_WRITEFUNCTION, write_callback);
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.SH DESCRIPTION
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Pass a pointer to your callback function, which should match the prototype
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shown above.
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This callback function gets called by libcurl as soon as there is data
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received that needs to be saved. For most transfers, this callback gets called
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many times and each invoke delivers another chunk of data. \fIptr\fP points to
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the delivered data, and the size of that data is \fInmemb\fP; \fIsize\fP is
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always 1.
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The callback function will be passed as much data as possible in all invokes,
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but you must not make any assumptions. It may be one byte, it may be
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thousands. The maximum amount of body data that will be passed to the write
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callback is defined in the curl.h header file: \fICURL_MAX_WRITE_SIZE\fP (the
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usual default is 16K). If \fICURLOPT_HEADER(3)\fP is enabled, which makes
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header data get passed to the write callback, you can get up to
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\fICURL_MAX_HTTP_HEADER\fP bytes of header data passed into it. This usually
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means 100K.
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This function may be called with zero bytes data if the transferred file is
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empty.
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The data passed to this function will not be null-terminated!
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Set the \fIuserdata\fP argument with the \fICURLOPT_WRITEDATA(3)\fP option.
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Your callback should return the number of bytes actually taken care of. If
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that amount differs from the amount passed to your callback function, it'll
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signal an error condition to the library. This will cause the transfer to get
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aborted and the libcurl function used will return \fICURLE_WRITE_ERROR\fP.
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If your callback function returns CURL_WRITEFUNC_PAUSE it will cause this
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transfer to become paused. See \fIcurl_easy_pause(3)\fP for further details.
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Set this option to NULL to get the internal default function used instead of
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your callback. The internal default function will write the data to the FILE *
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given with \fICURLOPT_WRITEDATA(3)\fP.
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This option doesn't enable HSTS, you need to use \fICURLOPT_HSTS_CTRL(3)\fP to
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do that.
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.SH DEFAULT
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libcurl will use 'fwrite' as a callback by default.
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.SH PROTOCOLS
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For all protocols
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.SH EXAMPLE
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.nf
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struct memory {
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char *response;
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size_t size;
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};
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static size_t cb(void *data, size_t size, size_t nmemb, void *userp)
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{
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size_t realsize = size * nmemb;
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struct memory *mem = (struct memory *)userp;
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char *ptr = realloc(mem->response, mem->size + realsize + 1);
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if(ptr == NULL)
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return 0; /* out of memory! */
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mem->response = ptr;
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memcpy(&(mem->response[mem->size]), data, realsize);
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mem->size += realsize;
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mem->response[mem->size] = 0;
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return realsize;
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}
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struct memory chunk = {0};
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/* send all data to this function */
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curl_easy_setopt(curl_handle, CURLOPT_WRITEFUNCTION, cb);
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/* we pass our 'chunk' struct to the callback function */
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curl_easy_setopt(curl_handle, CURLOPT_WRITEDATA, (void *)&chunk);
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.fi
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.SH AVAILABILITY
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Support for the CURL_WRITEFUNC_PAUSE return code was added in version 7.18.0.
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.SH RETURN VALUE
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This will return CURLE_OK.
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.SH "SEE ALSO"
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.BR CURLOPT_WRITEDATA "(3), " CURLOPT_READFUNCTION "(3), "
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.BR CURLOPT_HEADERFUNCTION "(3), "
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