CURLOPT_POSTFIELDS.3: explain the 100-continue magic better

diff --git a/docs/libcurl/opts/CURLOPT_POSTFIELDS.3 b/docs/libcurl/opts/CURLOPT_POSTFIELDS.3
index 17ec2d76f761ef5cb98286e030bee6cb51ead9cb..515376babf335d0dac8757839c95e087a1fedc3c 100644 (file)
--- a/docs/libcurl/opts/CURLOPT_POSTFIELDS.3
+++ b/docs/libcurl/opts/CURLOPT_POSTFIELDS.3
@@ -5,7 +5,7 @@
 .\" *                            | (__| |_| |  _ <| |___
 .\" *                             \___|\___/|_| \_\_____|
 .\" *
-.\" * Copyright (C) 1998 - 2014, Daniel Stenberg, <daniel@haxx.se>, et al.
+.\" * Copyright (C) 1998 - 2017, 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
@@ -52,8 +52,10 @@ the POST data from the read callback. If you want to send a zero-byte POST set
 \fICURLOPT_POSTFIELDS(3)\fP to an empty string, or set \fICURLOPT_POST(3)\fP to
 1 and \fICURLOPT_POSTFIELDSIZE(3)\fP to 0.
 
-Using POST with HTTP 1.1 implies the use of a "Expect: 100-continue" header.
-You can disable this header with \fICURLOPT_HTTPHEADER(3)\fP as usual.
+Using POST with HTTP 1.1 implies the use of a "Expect: 100-continue" header,
+and libcurl will add that header automatically if the POST is either known to
+be larger than 1024 bytes or if the expected size is unknown. You can disable
+this header with \fICURLOPT_HTTPHEADER(3)\fP as usual.
 
 To make multipart/formdata posts (aka RFC2388-posts), check out the
 \fICURLOPT_HTTPPOST(3)\fP option combined with \fIcurl_formadd(3)\fP.