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CURLOPT_XFERINFOFUNCTION(3)         libcurl        CURLOPT_XFERINFOFUNCTION(3)

NAME
       CURLOPT_XFERINFOFUNCTION - progress meter callback

SYNOPSIS
       #include <curl/curl.h>

       int progress_callback(void *clientp,
                             curl_off_t dltotal,
                             curl_off_t dlnow,
                             curl_off_t ultotal,
                             curl_off_t ulnow);

       CURLcode curl_easy_setopt(CURL *handle, CURLOPT_XFERINFOFUNCTION,
                                 progress_callback);

DESCRIPTION
       Pass a pointer to your callback function, which should match the
       prototype shown above.

       This function gets called by libcurl instead of its internal equivalent
       with a frequent interval. While data is being transferred it will be
       called frequently, and during slow periods like when nothing is being
       transferred it can slow down to about one call per second.

       clientp is the pointer set with CURLOPT_XFERINFODATA(3), it is not used
       by libcurl but is only passed along from the application to the
       callback.

       The callback gets told how much data libcurl will transfer and has
       transferred, in number of bytes. dltotal is the total number of bytes
       libcurl expects to download in this transfer. dlnow is the number of
       bytes downloaded so far. ultotal is the total number of bytes libcurl
       expects to upload in this transfer. ulnow is the number of bytes
       uploaded so far.

       Unknown/unused argument values passed to the callback will be set to
       zero (like if you only download data, the upload size will remain 0).
       Many times the callback will be called one or more times first, before
       it knows the data sizes so a program must be made to handle that.

       If your callback function returns CURL_PROGRESSFUNC_CONTINUE it will
       cause libcurl to continue executing the default progress function.

       Returning any other non-zero value from this callback will cause
       libcurl to abort the transfer and return CURLE_ABORTED_BY_CALLBACK.

       If you transfer data with the multi interface, this function will not
       be called during periods of idleness unless you call the appropriate
       libcurl function that performs transfers.

       CURLOPT_NOPROGRESS(3) must be set to 0 to make this function actually
       get called.

DEFAULT
       By default, libcurl has an internal progress meter. That is rarely
       wanted by users.

PROTOCOLS
       All

EXAMPLE
        struct progress {
          char *private;
          size_t size;
        };

        static size_t progress_callback(void *clientp,
                                        curl_off_t dltotal,
                                        curl_off_t dlnow,
                                        curl_off_t ultotal,
                                        curl_off_t ulnow)
        {
          struct progress *memory = (struct progress *)clientp;

          /* use the values */

          return 0; /* all is good */
        }

        struct progress data;

        /* pass struct to callback  */
        curl_easy_setopt(curl_handle, CURLOPT_XFERINFODATA, &data);

        curl_easy_setopt(curl_handle, CURLOPT_XFERINFOFUNCTION, progress_callback);

AVAILABILITY
       Added in 7.32.0. This callback replaces CURLOPT_PROGRESSFUNCTION(3)

RETURN VALUE
       Returns CURLE_OK.

SEE ALSO
       CURLOPT_XFERINFODATA(3), CURLOPT_NOPROGRESS(3),

ibcurl 8.1.2                    April 26, 2023     CURLOPT_XFERINFOFUNCTION(3)