docs: tweak 'rm -f' limitations

Based on http://debbugs.gnu.org/10819 and
http://austingroupbugs.net/view.php?id=542

* doc/autoconf.texi (Limitations of Usual Tools) <rm>: More
details on 'rm -f' without files.

Signed-off-by: Eric Blake <eblake@redhat.com>

diff --git a/doc/autoconf.texi b/doc/autoconf.texi
index 82837a2ba4e7b287520eb8d3ab23aa5d382fce18..607d8dcd78d7cfed19dd96f00e0093c828f712c9 100644 (file)
--- a/doc/autoconf.texi
+++ b/doc/autoconf.texi
@@ -19225,10 +19225,12 @@ This problem no longer exists in Mac OS X 10.4.3.
 @prindex @command{rm}
 The @option{-f} and @option{-r} options are portable.
 
-It is not portable to invoke @command{rm} without operands.  For
-example, on many systems @samp{rm -f -r} (with no other arguments)
-silently succeeds without doing anything, but it fails with a diagnostic
-on NetBSD 2.0.2.
+It is not portable to invoke @command{rm} without options or operands.
+On the other hand, Posix now requires @command{rm -f} to silently
+succeed when there are no operands (useful for constructs like
+@command{rm -rf $filelist} without first checking if @samp{$filelist}
+was empty).  But this was not always portable; at least NetBSD
+@command{rm} built before 2008 would fail with a diagnostic.
 
 A file might not be removed even if its parent directory is writable
 and searchable.  Many Posix hosts cannot remove a mount point, a named