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Diffstat (limited to 'docs/libcurl/opts/GNURLOPT_WRITEFUNCTION.3')
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diff --git a/docs/libcurl/opts/GNURLOPT_WRITEFUNCTION.3 b/docs/libcurl/opts/GNURLOPT_WRITEFUNCTION.3 new file mode 100644 index 000000000..3a5162306 --- /dev/null +++ b/docs/libcurl/opts/GNURLOPT_WRITEFUNCTION.3 @@ -0,0 +1,83 @@ +.\" ************************************************************************** +.\" * _ _ ____ _ +.\" * Project ___| | | | _ \| | +.\" * / __| | | | |_) | | +.\" * | (__| |_| | _ <| |___ +.\" * \___|\___/|_| \_\_____| +.\" * +.\" * Copyright (C) 1998 - 2018, Daniel Stenberg, <daniel@haxx.se>, et al. +.\" * +.\" * This software is licensed as described in the file COPYING, which +.\" * you should have received as part of this distribution. The terms +.\" * are also available at https://curl.haxx.se/docs/copyright.html. +.\" * +.\" * You may opt to use, copy, modify, merge, publish, distribute and/or sell +.\" * copies of the Software, and permit persons to whom the Software is +.\" * furnished to do so, under the terms of the COPYING file. +.\" * +.\" * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY +.\" * KIND, either express or implied. +.\" * +.\" ************************************************************************** +.\" +.TH CURLOPT_WRITEFUNCTION 3 "16 Jun 2014" "libcurl 7.37.0" "curl_easy_setopt options" +.SH NAME +CURLOPT_WRITEFUNCTION \- set callback for writing received data +.SH SYNOPSIS +.nf +#include <gnurl/curl.h> + +size_t write_callback(char *ptr, size_t size, size_t nmemb, void *userdata); + +CURLcode curl_easy_setopt(CURL *handle, CURLOPT_WRITEFUNCTION, write_callback); +.SH DESCRIPTION +Pass a pointer to your callback function, which should match the prototype +shown above. + +This callback function gets called by libcurl as soon as there is data +received that needs to be saved. For most transfers, this callback gets called +many times and each invoke delivers another chunk of data. \fIptr\fP points to +the delivered data, and the size of that data is \fInmemb\fP; \fIsize\fP is +always 1. + +The callback function will be passed as much data as possible in all invokes, +but you must not make any assumptions. It may be one byte, it may be +thousands. The maximum amount of body data that will be passed to the write +callback is defined in the curl.h header file: \fICURL_MAX_WRITE_SIZE\fP (the +usual default is 16K). If \fICURLOPT_HEADER(3)\fP is enabled, which makes +header data get passed to the write callback, you can get up to +\fICURL_MAX_HTTP_HEADER\fP bytes of header data passed into it. This usually +means 100K. + +This function may be called with zero bytes data if the transferred file is +empty. + +The data passed to this function will not be zero terminated! + +Set the \fIuserdata\fP argument with the \fICURLOPT_WRITEDATA(3)\fP option. + +Your callback should return the number of bytes actually taken care of. If +that amount differs from the amount passed to your callback function, it'll +signal an error condition to the library. This will cause the transfer to get +aborted and the libcurl function used will return \fICURLE_WRITE_ERROR\fP. + +If your callback function returns CURL_WRITEFUNC_PAUSE it will cause this +transfer to become paused. See \fIcurl_easy_pause(3)\fP for further details. + +Set this option to NULL to get the internal default function used instead of +your callback. The internal default function will write the data to the FILE * +given with \fICURLOPT_WRITEDATA(3)\fP. +.SH DEFAULT +libcurl will use 'fwrite' as a callback by default. +.SH PROTOCOLS +For all protocols +.SH AVAILABILITY +Support for the CURL_WRITEFUNC_PAUSE return code was added in version 7.18.0. +.SH RETURN VALUE +This will return CURLE_OK. +.SH EXAMPLE +A common technique is to use this callback to store the incoming data into a +dynamically growing allocated buffer. Like in the getinmemory example: +https://curl.haxx.se/libcurl/c/getinmemory.html +.SH "SEE ALSO" +.BR CURLOPT_WRITEDATA "(3), " CURLOPT_READFUNCTION "(3), " |