NAME

       CURLOPT_WRITEFUNCTION - set callback for writing received data

SYNOPSIS

       #include <curl/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);

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.  ptr points to the delivered  data,  and  the  size  of  that  data  is  size
       multiplied with nmemb.

       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:
       CURL_MAX_WRITE_SIZE (the usual default is 16K). If  CURLOPT_HEADER(3)  is  enabled,  which
       makes header data get passed to the write callback, you can get up to CURL_MAX_HTTP_HEADER
       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 userdata argument with the CURLOPT_WRITEDATA(3) 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 CURLE_WRITE_ERROR.

       If  your  callback  function  returns  CURL_WRITEFUNC_PAUSE it will cause this transfer to
       become paused.  See curl_easy_pause(3) 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
       CURLOPT_WRITEDATA(3).

DEFAULT

       libcurl will use 'fwrite' as a callback by default.

PROTOCOLS

       For all protocols

AVAILABILITY

       Support for the CURL_WRITEFUNC_PAUSE return code was added in version 7.18.0.

RETURN VALUE

       This will return CURLE_OK.

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

SEE ALSO

       CURLOPT_WRITEDATA(3), CURLOPT_READFUNCTION(3),