CURLOPT_XFERINFOFUNCTION(3)

1CURLOPT_XFERINFOFUNCTION(3)curl_easy_setopt optionsCURLOPT_XFERINFOFUNCTION(3)
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NAME

6       CURLOPT_XFERINFOFUNCTION - progress meter callback
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SYNOPSIS

9       #include <curl/curl.h>
10
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.
23
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  up‐
38       loaded 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       If your callback function returns  CURL_PROGRESSFUNC_CONTINUE  it  will
46       cause libcurl to continue executing the default progress function.
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48       Returning  any  other  non-zero  value  from  this  callback will cause
49       libcurl to abort the transfer and return CURLE_ABORTED_BY_CALLBACK.
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51       If you transfer data with the multi interface, this function  will  not
52       be  called  during  periods of idleness unless you call the appropriate
53       libcurl function that performs transfers.
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55       CURLOPT_NOPROGRESS(3) must be set to 0 to make this  function  actually
56       get called.
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DEFAULT

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

63       All
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EXAMPLE

66        struct progress {
67          char *private;
68          size_t size;
69        };
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71        static size_t progress_callback(void *clientp,
72                                        curl_off_t dltotal,
73                                        curl_off_t dlnow,
74                                        curl_off_t ultotal,
75                                        curl_off_t ulnow)
76        {
77          struct memory *progress = (struct progress *)userp;
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79          /* use the values */
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81          return 0; /* all is good */
82        }
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84        struct progress data;
85
86        /* pass struct to callback  */
87        curl_easy_setopt(curl_handle, CURLOPT_XFERINFODATA, &data);
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89        curl_easy_setopt(curl_handle, CURLOPT_XFERINFOFUNCTION, progress_callback);
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AVAILABILITY

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

95       Returns CURLE_OK.
96