CURLOPT_XFERINFOFUNCTION(3)

1CURLOPT_XFERINFOFUNCTION(3)         libcurl        CURLOPT_XFERINFOFUNCTION(3)
2
3
4

NAME

6       CURLOPT_XFERINFOFUNCTION - progress meter callback
7

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);
16
17       CURLcode curl_easy_setopt(CURL *handle, CURLOPT_XFERINFOFUNCTION,
18                                 progress_callback);
19

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 frequently, and during slow periods like when nothing  is  being
27       transferred it can slow down to about one call per second.
28
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.
32
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.
39
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.
44
45       If  your  callback  function returns CURL_PROGRESSFUNC_CONTINUE it will
46       cause libcurl to continue executing the default progress function.
47
48       Returning any other  non-zero  value  from  this  callback  will  cause
49       libcurl to abort the transfer and return CURLE_ABORTED_BY_CALLBACK.
50
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.
54
55       CURLOPT_NOPROGRESS(3)  must  be set to 0 to make this function actually
56       get called.
57

DEFAULT

59       By default, libcurl has an internal  progress  meter.  That  is  rarely
60       wanted by users.
61

PROTOCOLS

63       All
64

EXAMPLE

66        struct progress {
67          char *private;
68          size_t size;
69        };
70
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 progress *memory = (struct progress *)clientp;
78
79          /* use the values */
80
81          return 0; /* all is good */
82        }
83
84        struct progress data;
85
86        /* pass struct to callback  */
87        curl_easy_setopt(curl_handle, CURLOPT_XFERINFODATA, &data);
88
89        curl_easy_setopt(curl_handle, CURLOPT_XFERINFOFUNCTION, progress_callback);
90

AVAILABILITY

92       Added in 7.32.0. This callback replaces CURLOPT_PROGRESSFUNCTION(3)
93

RETURN VALUE

95       Returns CURLE_OK.
96