CURLOPT_XFERINFOFUNCTION(3)

1CURLOPT_XFERINFOFUNCTION(3)curl_easy_setopt optionsCURLOPT_XFERINFOFUNCTION(3)
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NAME

6       CURLOPT_XFERINFOFUNCTION - callback to progress meter function
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SYNOPSIS

9       #include <curl/curl.h>
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11       int progress_callback(void *clientp,
12                             curl_off_t dltotal,
13                             curl_off_t dlnow,
14                             curl_off_t ultotal,
15                             curl_off_t ulnow);
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17       CURLcode   curl_easy_setopt(CURL   *handle,   CURLOPT_XFERINFOFUNCTION,
18       progress_callback);
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DESCRIPTION

21       Pass a pointer to your callback function, which should match the proto‐
22       type shown above.
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24       This function gets called by libcurl instead of its internal equivalent
25       with a frequent interval. While data is being transferred  it  will  be
26       called  very  frequently,  and during slow periods like when nothing is
27       being transferred it can slow down to about one call per second.
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29       clientp is the pointer set with CURLOPT_XFERINFODATA(3), it is not used
30       by  libcurl  but is only passed along from the application to the call‐
31       back.
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33       The callback gets told how much data  libcurl  will  transfer  and  has
34       transferred,  in  number of bytes. dltotal is the total number of bytes
35       libcurl expects to download in this transfer. dlnow is  the  number  of
36       bytes  downloaded  so far. ultotal is the total number of bytes libcurl
37       expects to upload in this  transfer.  ulnow  is  the  number  of  bytes
38       uploaded so far.
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40       Unknown/unused  argument  values  passed to the callback will be set to
41       zero (like if you only download data, the upload size will  remain  0).
42       Many  times the callback will be called one or more times first, before
43       it knows the data sizes so a program must be made to handle that.
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45       Returning a non-zero value from this callback  will  cause  libcurl  to
46       abort the transfer and return CURLE_ABORTED_BY_CALLBACK.
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48       If  you  transfer data with the multi interface, this function will not
49       be called during periods of idleness unless you  call  the  appropriate
50       libcurl function that performs transfers.
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52       CURLOPT_NOPROGRESS(3)  must  be set to 0 to make this function actually
53       get called.
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DEFAULT

56       By default, libcurl has  an  internal  progress  meter.  That's  rarely
57       wanted by users.
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PROTOCOLS

60       All
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EXAMPLE

63       https://curl.haxx.se/libcurl/c/progressfunc.html
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AVAILABILITY

66       Added in 7.32.0. This callback replaces CURLOPT_PROGRESSFUNCTION(3)
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RETURN VALUE

69       Returns CURLE_OK.
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