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authorDaniel Stenberg <daniel@haxx.se>2018-02-16 11:23:12 +0100
committerDaniel Stenberg <daniel@haxx.se>2018-02-16 22:54:51 +0100
commit174212972c5d508cf54664f97217d5fe63134490 (patch)
tree879dfbc0f65385d733f9e6cfbcf72a4c5b3cd5d3
parent70cbb921348db5193549efbe30877a0398b559a0 (diff)
CURLOPT_HEADER.3: clarify problems with different data sizes
-rw-r--r--docs/libcurl/opts/CURLOPT_HEADER.318
1 files changed, 12 insertions, 6 deletions
diff --git a/docs/libcurl/opts/CURLOPT_HEADER.3 b/docs/libcurl/opts/CURLOPT_HEADER.3
index b650163d1..76dea467e 100644
--- a/docs/libcurl/opts/CURLOPT_HEADER.3
+++ b/docs/libcurl/opts/CURLOPT_HEADER.3
@@ -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.