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CURLOPT_HEADER(3) curl_easy_setopt options CURLOPT_HEADER(3)
CURLOPT_HEADER - pass headers to the data stream
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_HEADER, long onoff);
Pass the long value onoff set to 1 to ask libcurl to include the
headers in the write callback (CURLOPT_WRITEFUNCTION(3)). This option
is relevant for protocols that actually have headers or other meta-data
(like HTTP and FTP).
When asking to get the headers passed to the same callback as the body,
it is not possible to accurately separate them again without detailed
knowledge about the protocol in use.
Further: the CURLOPT_WRITEFUNCTION(3) callback is limited to only ever
get a maximum of CURL_MAX_WRITE_SIZE bytes passed to it (16KB), while a
header can be longer and the CURLOPT_HEADERFUNCTION(3) supports getting
called with headers up to CURL_MAX_HTTP_HEADER bytes big (100KB).
It is often better to use CURLOPT_HEADERFUNCTION(3) to get the header
While named confusingly similar, CURLOPT_HTTPHEADER(3) is used to set
custom HTTP headers!
CURL *curl = curl_easy_init();
curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
curl_easy_setopt(curl, CURLOPT_HEADER, 1L);
libcurl 7.73.0 September 16, 2020 CURLOPT_HEADER(3)