1--- 2c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al. 3SPDX-License-Identifier: curl 4Title: CURLOPT_BUFFERSIZE 5Section: 3 6Source: libcurl 7See-also: 8 - CURLOPT_MAXFILESIZE (3) 9 - CURLOPT_MAX_RECV_SPEED_LARGE (3) 10 - CURLOPT_UPLOAD_BUFFERSIZE (3) 11 - CURLOPT_WRITEFUNCTION (3) 12Protocol: 13 - All 14--- 15 16# NAME 17 18CURLOPT_BUFFERSIZE - receive buffer size 19 20# SYNOPSIS 21 22~~~c 23#include <curl/curl.h> 24 25CURLcode curl_easy_setopt(CURL *handle, CURLOPT_BUFFERSIZE, long size); 26~~~ 27 28# DESCRIPTION 29 30Pass a long specifying your preferred *size* (in bytes) for the receive buffer 31in libcurl. The main point of this would be that the write callback gets 32called more often and with smaller chunks. Secondly, for some protocols, there 33is a benefit of having a larger buffer for performance. 34 35This is just treated as a request, not an order. You cannot be guaranteed to 36actually get the given size. 37 38This buffer size is by default *CURL_MAX_WRITE_SIZE* (16kB). The maximum 39buffer size allowed to be set is *CURL_MAX_READ_SIZE* (10MB). The minimum 40buffer size allowed to be set is 1024. 41 42DO NOT set this option on a handle that is currently used for an active 43transfer as that may lead to unintended consequences. 44 45The maximum size was 512kB until 7.88.0. 46 47Starting in libcurl 8.7.0, there is just a single transfer buffer allocated 48per multi handle. This buffer is used by all easy handles added to a multi 49handle no matter how many parallel transfers there are. The buffer remains 50allocated as long as there are active transfers. 51 52# DEFAULT 53 54CURL_MAX_WRITE_SIZE (16kB) 55 56# EXAMPLE 57 58~~~c 59int main(void) 60{ 61 CURL *curl = curl_easy_init(); 62 if(curl) { 63 CURLcode res; 64 curl_easy_setopt(curl, CURLOPT_URL, "sftp://example.com/foo.bin"); 65 66 /* ask libcurl to allocate a larger receive buffer */ 67 curl_easy_setopt(curl, CURLOPT_BUFFERSIZE, 120000L); 68 69 res = curl_easy_perform(curl); 70 71 curl_easy_cleanup(curl); 72 } 73} 74~~~ 75 76# AVAILABILITY 77 78Added in 7.10. Growing the buffer was added in 7.53.0. 79 80# RETURN VALUE 81 82Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not. 83