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CURLOPT_HEADER(3) Library Functions Manual CURLOPT_HEADER(3) NAME CURLOPT_HEADER - pass headers to the data stream SYNOPSIS #include <curl/curl.h> CURLcode curl_easy_setopt(CURL *handle, CURLOPT_HEADER, long onoff); DESCRIPTION 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 knowl- edge 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 data separately. While named confusingly similar, CURLOPT_HTTPHEADER(3) is used to set cus- tom HTTP headers. DEFAULT 0 PROTOCOLS This functionality affects ftp, http, imap, pop3 and smtp EXAMPLE int main(void) { CURL *curl = curl_easy_init(); if(curl) { CURLcode result; curl_easy_setopt(curl, CURLOPT_URL, "https://example.com"); curl_easy_setopt(curl, CURLOPT_HEADER, 1L); result = curl_easy_perform(curl); curl_easy_cleanup(curl); } } AVAILABILITY Added in curl 7.1 RETURN VALUE curl_easy_setopt(3) returns a CURLcode indicating success or error. CURLE_OK (0) means everything was OK, non-zero means an error occurred, see libcurl-errors(3). SEE ALSO CURLOPT_HEADERFUNCTION(3), CURLOPT_HTTPHEADER(3) libcurl 2026-06-11 CURLOPT_HEADER(3)
NAME | SYNOPSIS | DESCRIPTION | DEFAULT | PROTOCOLS | EXAMPLE | AVAILABILITY | RETURN VALUE | SEE ALSO
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