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

4 files changed, 20 insertions, 3 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
diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index 6c8f118c8a3..0cc5b7fe71c 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,3 +1,7 @@
+2014-06-26  Glenn Morris  <rgm@gnu.org>
+
+        * subr.el (read-passwd): Warn about batch mode.  (Bug#17839)
+
 2014-06-26  Daiki Ueno  <ueno@gnu.org>
 
         * emacs-lisp/package.el (package--check-signature):
diff --git a/lisp/subr.el b/lisp/subr.el
index 700c072a81b..ac0e130b4e0 100644
--- a/lisp/subr.el
+++ b/lisp/subr.el
@@ -2006,6 +2006,7 @@ If optional CONFIRM is non-nil, read the password twice to make sure.
 Optional DEFAULT is a default password to use instead of empty input.
 
 This function echoes `.' for each character that the user types.
+Note that in batch mode, the input is not hidden!
 
 Once the caller uses the password, it can erase the password
 by doing (clear-string STRING)."
@@ -2045,7 +2046,11 @@ by doing (clear-string STRING)."
             (add-hook 'after-change-functions hide-chars-fun nil 'local))
         (unwind-protect
             (let ((enable-recursive-minibuffers t))
-              (read-string prompt nil t default)) ; t = "no history"
+              (read-string
+               (if noninteractive
+                   (format "%s[INPUT WILL NOT BE HIDDEN!] " prompt) ; bug#17839
+                 prompt)
+               nil t default)) ; t = "no history"
           (when (buffer-live-p minibuf)
             (with-current-buffer minibuf
               ;; Not sure why but it seems that there might be cases where the