Section: curl_easy_setopt options (3)
Updated: August 18, 2018
CURLOPT_UPLOAD_BUFFERSIZE - set preferred upload buffer size
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_UPLOAD_BUFFERSIZE, long size);
Pass a long specifying your preferred size
(in bytes) for the upload
buffer in libcurl. It makes libcurl uses a larger buffer that gets passed to
the next layer in the stack to get sent off. In some setups and for some
protocols, there's a huge performance benefit of having a larger upload
This is just treated as a request, not an order. You cannot be guaranteed to
actually get the given size.
The upload buffer size is by default 64 kilobytes. The maximum buffer size
allowed to be set is 2 megabytes. The minimum buffer size allowed to be set is
Since curl 7.61.1 the upload buffer is allocated on-demand - so if the handle
isn't used for upload, this buffer will not be allocated at all.
CURL *curl = curl_easy_init();
curl_easy_setopt(curl, CURLOPT_URL, "sftp://example.com/foo.bin");
/* ask libcurl to allocate a larger upload buffer */
curl_easy_setopt(curl, CURLOPT_UPLOAD_BUFFERSIZE, 120000L);
ret = curl_easy_perform(curl);
Added in 7.62.0.
Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.