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CURLOPT_HEADER.3: clarify problems with different data sizes

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Daniel Stenberg 2018-02-16 11:23:12 +01:00
parent 70cbb92134
commit 174212972c
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@ -5,7 +5,7 @@
.\" * | (__| |_| | _ <| |___
.\" * \___|\___/|_| \_\_____|
.\" *
.\" * Copyright (C) 1998 - 2015, Daniel Stenberg, <daniel@haxx.se>, et al.
.\" * Copyright (C) 1998 - 2018, Daniel Stenberg, <daniel@haxx.se>, et al.
.\" *
.\" * This software is licensed as described in the file COPYING, which
.\" * you should have received as part of this distribution. The terms
@ -28,14 +28,20 @@ CURLOPT_HEADER \- pass headers to the data stream
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_HEADER, long onoff);
.SH DESCRIPTION
Pass in \fIonoff\fP set to 1 to tell the library to include the header in the
body output for requests with this \fIhandle\fP. This option is relevant for
protocols that actually have headers or other meta-data (like HTTP and FTP).
Pass the long value \fIonoff\fP set to 1 to ask libcurl to include the headers
in the write callback (\fICURLOPT_WRITEFUNCTION(3)\fP). This option is
relevant for protocols that actually have headers or other meta-data (like
HTTP and FTP).
When asking to get the header info passed to the same callback as the body, it
is not possible to accurately separate them again without detailed knowledge
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 \fCURLOPT_WRITEFUNCTION(3)\fP callback is limited to only ever
get a maximum of \fICURL_MAX_WRITE_SIZE\fP bytes passed to it (16KB), while a
header can be longer and the \fICURLOPT_HEADERFUNCTION(3)\fP supports getting
called with headers up to \fICURL_MAX_HTTP_HEADER\fP bytes big (100KB).
It is often better to use \fICURLOPT_HEADERFUNCTION(3)\fP to get the header
data separately.