Warn about read-passwd in batch mode

* doc/lispref/minibuf.texi (Intro to Minibuffers): Batch mode is basic.
(Reading a Password): Mention batch mode. 

* lisp/subr.el (read-passwd): Warn about batch mode.

Fixes: debbugs:17839

2 files changed, 10 insertions, 2 deletions

diff --git a/doc/lispref/ChangeLog b/doc/lispref/ChangeLog
index 4610c33796a..6b673e7f329 100644
--- a/doc/lispref/ChangeLog
+++ b/doc/lispref/ChangeLog
@@ -1,3 +1,8 @@
+2014-06-26  Glenn Morris  <rgm@gnu.org>
+
+        * minibuf.texi (Intro to Minibuffers): Batch mode is basic.
+        (Reading a Password): Mention batch mode.  (Bug#17839)
+
 2014-06-21  Eli Zaretskii  <eliz@gnu.org>
 
         * positions.texi (Screen Lines): Clarify how columns are counted
diff --git a/doc/lispref/minibuf.texi b/doc/lispref/minibuf.texi
index 5b4e29c57a3..4a94f41d732 100644
--- a/doc/lispref/minibuf.texi
+++ b/doc/lispref/minibuf.texi
@@ -101,7 +101,9 @@ the minibuffer is in a separate frame.  @xref{Minibuffers and Frames}.
 
   When Emacs is running in batch mode, any request to read from the
 minibuffer actually reads a line from the standard input descriptor that
-was supplied when Emacs was started.
+was supplied when Emacs was started.  This supports only basic input:
+none of the special minibuffer features (history, completion,
+password hiding, etc.) are available in batch mode.
 
 @node Text from Minibuffer
 @section Reading Text Strings with the Minibuffer
@@ -2123,7 +2125,8 @@ function @code{read-passwd}.
 @defun read-passwd prompt &optional confirm default
 This function reads a password, prompting with @var{prompt}.  It does
 not echo the password as the user types it; instead, it echoes @samp{.}
-for each character in the password.
+for each character in the password.  (Note that in batch mode, the
+input is not hidden.)
 
 The optional argument @var{confirm}, if non-@code{nil}, says to read the
 password twice and insist it must be the same both times.  If it isn't