CURLOPT_PROGRESSFUNCTION(3)

1CURLOPT_PROGRESSFUNCTION(3)curl_easy_setopt optionsCURLOPT_PROGRESSFUNCTION(3)
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NAME

6       CURLOPT_PROGRESSFUNCTION - 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                             double dltotal,
13                             double dlnow,
14                             double ultotal,
15                             double ulnow);
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17       CURLcode   curl_easy_setopt(CURL   *handle,   CURLOPT_PROGRESSFUNCTION,
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       We  encourage  users  to  use the newer CURLOPT_XFERINFOFUNCTION(3) in‐
25       stead, if you can.
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27       This function gets called by libcurl instead of its internal equivalent
28       with  a  frequent  interval. While data is being transferred it will be
29       called very frequently, and during slow periods like  when  nothing  is
30       being transferred it can slow down to about one call per second.
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32       clientp is the pointer set with CURLOPT_PROGRESSDATA(3), it is not used
33       by libcurl but is only passed along from the application to  the  call‐
34       back.
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36       The  callback  gets  told  how  much data libcurl will transfer and has
37       transferred, in number of bytes. dltotal is the total number  of  bytes
38       libcurl  expects  to  download in this transfer. dlnow is the number of
39       bytes downloaded so far. ultotal is the total number of  bytes  libcurl
40       expects  to  upload  in this transfer. ulnow is the number of bytes up‐
41       loaded so far.
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43       Unknown/unused argument values passed to the callback will  be  set  to
44       zero  (like  if you only download data, the upload size will remain 0).
45       Many times the callback will be called one or more times first,  before
46       it knows the data sizes so a program must be made to handle that.
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48       If  your  callback  function returns CURL_PROGRESSFUNC_CONTINUE it will
49       cause libcurl to continue executing the default progress function.
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51       Returning any other  non-zero  value  from  this  callback  will  cause
52       libcurl to abort the transfer and return CURLE_ABORTED_BY_CALLBACK.
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54       If  you  transfer data with the multi interface, this function will not
55       be called during periods of idleness unless you  call  the  appropriate
56       libcurl function that performs transfers.
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58       CURLOPT_NOPROGRESS(3)  must  be set to 0 to make this function actually
59       get called.
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DEFAULT

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

66       All
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EXAMPLE

69       https://curl.se/libcurl/c/progressfunc.html
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AVAILABILITY

72       Always
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RETURN VALUE

75       Returns CURLE_OK.
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