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23 .TH CURLOPT_XFERINFOFUNCTION 3 "February 03, 2016" "libcurl 7.59.0" "curl_easy_setopt options"
26 CURLOPT_XFERINFOFUNCTION \- callback to progress meter function
28 #include <curl/curl.h>
30 int progress_callback(void *clientp,
36 CURLcode curl_easy_setopt(CURL *handle, CURLOPT_XFERINFOFUNCTION, progress_callback);
38 Pass a pointer to your callback function, which should match the prototype
41 This function gets called by libcurl instead of its internal equivalent with a
42 frequent interval. While data is being transferred it will be called very
43 frequently, and during slow periods like when nothing is being transferred it
44 can slow down to about one call per second.
46 \fIclientp\fP is the pointer set with \fICURLOPT_XFERINFODATA(3)\fP, it is not
47 used by libcurl but is only passed along from the application to the callback.
49 The callback gets told how much data libcurl will transfer and has
50 transferred, in number of bytes. \fIdltotal\fP is the total number of bytes
51 libcurl expects to download in this transfer. \fIdlnow\fP is the number of
52 bytes downloaded so far. \fIultotal\fP is the total number of bytes libcurl
53 expects to upload in this transfer. \fIulnow\fP is the number of bytes
56 Unknown/unused argument values passed to the callback will be set to zero
57 (like if you only download data, the upload size will remain 0). Many times
58 the callback will be called one or more times first, before it knows the data
59 sizes so a program must be made to handle that.
61 Returning a non-zero value from this callback will cause libcurl to abort the
62 transfer and return \fICURLE_ABORTED_BY_CALLBACK\fP.
64 If you transfer data with the multi interface, this function will not be
65 called during periods of idleness unless you call the appropriate libcurl
66 function that performs transfers.
68 \fICURLOPT_NOPROGRESS(3)\fP must be set to 0 to make this function actually
71 By default, libcurl has an internal progress meter. That's rarely wanted by
76 https://curl.haxx.se/libcurl/c/progressfunc.html
78 Added in 7.32.0. This callback replaces \fICURLOPT_PROGRESSFUNCTION(3)\fP
82 .BR CURLOPT_XFERINFODATA "(3), " CURLOPT_NOPROGRESS "(3), "