1---
2c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
3SPDX-License-Identifier: curl
4Title: CURLOPT_PROGRESSFUNCTION
5Section: 3
6Source: libcurl
7See-also:
8  - CURLOPT_NOPROGRESS (3)
9  - CURLOPT_VERBOSE (3)
10  - CURLOPT_XFERINFOFUNCTION (3)
11Protocol:
12  - All
13Added-in: 7.1
14---
15
16# NAME
17
18CURLOPT_PROGRESSFUNCTION - progress meter callback
19
20# SYNOPSIS
21
22~~~c
23#include <curl/curl.h>
24
25int progress_callback(void *clientp,
26                      double dltotal,
27                      double dlnow,
28                      double ultotal,
29                      double ulnow);
30
31CURLcode curl_easy_setopt(CURL *handle, CURLOPT_PROGRESSFUNCTION,
32                          progress_callback);
33~~~
34
35# DESCRIPTION
36
37Pass a pointer to your callback function, which should match the prototype
38shown above.
39
40This option is deprecated and we encourage users to use the
41newer CURLOPT_XFERINFOFUNCTION(3) instead, if you can.
42
43This function gets called by libcurl instead of its internal equivalent with a
44frequent interval. While data is being transferred it is invoked frequently,
45and during slow periods like when nothing is being transferred it can slow
46down to about one call per second.
47
48*clientp* is the pointer set with CURLOPT_PROGRESSDATA(3), it is not
49used by libcurl but is only passed along from the application to the callback.
50
51The callback gets told how much data libcurl is about to transfer and has
52transferred, in number of bytes. *dltotal* is the total number of bytes
53libcurl expects to download in this transfer. *dlnow* is the number of
54bytes downloaded so far. *ultotal* is the total number of bytes libcurl
55expects to upload in this transfer. *ulnow* is the number of bytes
56uploaded so far.
57
58Unknown/unused argument values passed to the callback are be set to zero (like
59if you only download data, the upload size remains 0). Many times the callback
60is called one or more times first, before it knows the data sizes so a program
61must be made to handle that.
62
63Return zero from the callback if everything is fine.
64
65If your callback function returns CURL_PROGRESSFUNC_CONTINUE it causes libcurl
66to continue executing the default progress function.
67
68Return 1 from this callback to make libcurl abort the transfer and return
69*CURLE_ABORTED_BY_CALLBACK*.
70
71If you transfer data with the multi interface, this function is not called
72during periods of idleness unless you call the appropriate libcurl function
73that performs transfers.
74
75CURLOPT_NOPROGRESS(3) must be set to 0 to make this function actually
76get called.
77
78# DEFAULT
79
80NULL. libcurl has an internal progress meter. That is rarely wanted by users.
81
82# %PROTOCOLS%
83
84# EXAMPLE
85
86~~~c
87struct progress {
88  char *private;
89  size_t size;
90};
91
92static size_t progress_callback(void *clientp,
93                                double dltotal,
94                                double dlnow,
95                                double ultotal,
96                                double ulnow)
97{
98  struct progress *memory = clientp;
99  printf("private: %p\n", memory->private);
100
101  /* use the values */
102
103  return 0; /* all is good */
104}
105
106int main(void)
107{
108  struct progress data;
109
110  CURL *curl = curl_easy_init();
111  if(curl) {
112    /* pass struct to callback  */
113    curl_easy_setopt(curl, CURLOPT_PROGRESSDATA, &data);
114    curl_easy_setopt(curl, CURLOPT_PROGRESSFUNCTION, progress_callback);
115
116    curl_easy_perform(curl);
117  }
118}
119~~~
120
121# DEPRECATED
122
123Deprecated since 7.32.0.
124
125# %AVAILABILITY%
126
127# RETURN VALUE
128
129Returns CURLE_OK.
130