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To: bug-coreutils AT gnu DOT org
Cc: Eric Blake <ebb9 AT byu DOT net>, cygwin AT cygwin DOT com
Subject: Re: [Fwd: Strange-Dangerous behaviour in Cygwin]
References: <427CEB21 DOT 2010302 AT byu DOT net> <85ll6r3q5u DOT fsf AT pi DOT meyering DOT net>
From: Paul Eggert <eggert AT CS DOT UCLA DOT EDU>
Date: Sun, 08 May 2005 09:55:12 -0700
In-Reply-To: <85ll6r3q5u.fsf@pi.meyering.net> (Jim Meyering's message of "Sat, 07 May 2005 19:24:29 +0200")
Message-ID: <87k6m98xov.fsf@penguin.cs.ucla.edu>
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Jim Meyering <jim AT meyering DOT net> writes:

> Alternative opinions (or patches to yesno.c) welcome.

In the POSIX locale we don't have any choice; we have to accept
any answer with a leading "y" as "yes".  See:

http://www.opengroup.org/onlinepubs/000095399/basedefs/xbd_chap07.html#tag_07_03_06_01

Come to think of it, coreutils is too generous, as it ignores leading
white space; POSIX doesn't allow this, and Solaris 9 agrees with
POSIX.  GNU used to agree with POSIX until Ulrich Drepper's change
dated 1996 to use rpmatch if available, and I think the disagreement
with POSIX was unintended.  So I installed this patch.  (It's not
often that I get to fix one of his bugs!  :-)

2005-05-08  Paul Eggert  <eggert AT cs DOT ucla DOT edu>

	* NEWS: cp, ln, mv, rm no longer discard white space when intepreting
	responses.
	* lib/yesno.c: Include getline.h, not ctype.h.
	(yesno): Don't remove leading white space; POSIX doesn't allow it.
	Use getline to remove arbitrary restriction on response length.

--- NEWS	6 May 2005 17:56:49 -0000	1.286
+++ NEWS	8 May 2005 16:52:17 -0000
@@ -50,6 +50,12 @@ GNU coreutils NEWS                      
 
 ** Changes for better conformance to POSIX
 
+  cp, ln, mv, rm changes:
+
+    Leading white space is now significant in responses to yes-or-no questions.
+    For example, if "rm" asks "remove regular file `foo'?" and you respond
+    with " y" (i.e., space before "y"), it counts as "no".
+
   dd changes:
 
     On a QUIT or PIPE signal, dd now exits without printing statistics.
--- lib/yesno.c	4 Oct 2004 20:18:43 -0000	1.12
+++ lib/yesno.c	8 May 2005 16:46:42 -0000
@@ -1,5 +1,7 @@
 /* yesno.c -- read a yes/no response from stdin
-   Copyright (C) 1990, 1998, 2001, 2003, 2004 Free Software Foundation, Inc.
+
+   Copyright (C) 1990, 1998, 2001, 2003, 2004, 2005 Free Software
+   Foundation, Inc.
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -21,36 +23,31 @@
 
 #include "yesno.h"
 
-#include <ctype.h>
 #include <stdlib.h>
 #include <stdio.h>
 
-#if USE_UNLOCKED_IO
-# include "unlocked-io.h"
-#endif
+#include "getline.h"
 
-/* Read one line from standard input
-   and return nonzero if that line begins with y or Y,
-   otherwise return 0. */
+/* Return true if we read an affirmative line from standard input.  */
 
 extern int rpmatch (char const *response);
 
 bool
 yesno (void)
 {
-  /* We make some assumptions here:
-     a) leading white space in the response are not vital
-     b) the first 128 characters of the answer are enough (the rest can
-	be ignored)
-     I cannot think for a situation where this is not ok.  --drepper AT gnu  */
-  char buf[128];
-  int len = 0;
-  int c;
-
-  while ((c = getchar ()) != EOF && c != '\n')
-    if ((len > 0 && len < 127) || (len == 0 && !isspace (c)))
-      buf[len++] = c;
-  buf[len] = '\0';
+  char *response = NULL;
+  size_t response_size = 0;
+  ssize_t response_len = getline (&response, &response_size, stdin);
+  bool yes;
+
+  if (response_len <= 0)
+    yes = false;
+  else
+    {
+      response[response_len - 1] = '\0';
+      yes = (0 < rpmatch (response));
+    }
 
-  return rpmatch (buf) == 1;
+  free (response);
+  return yes;
 }

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