doc: stty: clarify that [-]drain is treated as an option

* doc/coreutils.texi (stty invocation): Say that "drain"
is treated as an option, rather than a line setting,
and so option processing rules apply to it.
Reported in https://bugs.debian.org/1018803

diff --git a/doc/coreutils.texi b/doc/coreutils.texi
index de819b6dc989a8507c13766a91e163ee9ed0f0d2..2af7616546234e550fd4343f45254fe33211ea37 100644 (file)
--- a/doc/coreutils.texi
+++ b/doc/coreutils.texi
@@ -15518,6 +15518,8 @@ Tell the kernel that the terminal has @var{n} columns.  Non-POSIX.
 @cindex nonblocking @command{stty} setting
 Apply settings after first waiting for pending output to be transmitted.
 This is enabled by default for GNU @command{stty}.
+Note this is treated as an option rather than a line setting,
+and will follow the option processing rules described in the summary above.
 It is useful to disable this option
 in cases where the system may be in a state where serial transmission
 is not possible.