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CURLOPT_UPLOAD_BUFFERSIZE(3) curl_easy_setopt options
CURLOPT_UPLOAD_BUFFERSIZE - 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 buffer.
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 16 kilobytes.
Since curl 7.61.1 the upload buffer is allocated on-demand - so if the
handle is not used for upload, this buffer will not be allocated at
DO NOT set this option on a handle that is currently used for an active
transfer as that may lead to unintended consequences.
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
libcurl 7.87.0 September 20, 2022 CURLOPT_UPLOAD_BUFFERSIZE(3)