Re: tramp (2.2.12); Retrieve of links attributes with stat fail when link contains two slashes.

[Pierre Téchoueyres]

        Hello everybody,

On Thu, Aug 20, 2015 at 09:28:09AM -0400, yary wrote:
> The nul character (ascii 0) is invalid in file/paths for most filesystems
> and can be safely used as a separator, if elisp strings and sed can handle
> them then that's the answer.
>

I've made some tests with stat and sed and it seems that stat support the null 
character only with --printf switch. sed seems to catch null with \o0.

For the fear of shell's handling of null char : the first problem is the stat 
program. Linux and BSD have differents options (and I don't know how it work 
on Solaris nor in HP*UX nor ...)
So maybe the solution is to first check for the version of stat and use an 
alist of options for each ones (maybe a custom option) but that's a bigger 
work.

Modified patch is at end of this e-mail


> -y
>
> On Thu, Aug 20, 2015 at 4:38 AM, Michael Albinus <address@hidden>
> wrote:
>
> > address@hidden (Pierre Téchoueyres) writes:
> >
> > >       Hello everybody,
> >
> > Hi Pierre,
> >
> > > After digging into the traces (thanks to `tramp-verbose'), I've found
> > > `tramp-do-file-attributes-with-stat' and
> > > `tramp-do-directory-files-and-attributes-with-stat'.
> > > On each of theses functions a replace of // is done.
> > >
> > > But this is done to workaround a bug in pdks on Opsware and I can't test
> > > it.
> > >
> > > The workaround I propose is to replace the //%N// of the stat command by
> > > **%N**. I thing it's impossible to create a link with stars (*) in name.
> >
> > Oh, it's possible:
> >
> > # touch /tmp/\*\*tmp\*\*
> > # ln -s /tmp/\*\*tmp\*\* /tmp/\*\*\*tmp\*\*\*
> > # ls -al /tmp/*tmp*
> > lrwxrwxrwx 1 albinus albinus   12 Aug 20 10:00 /tmp/***tmp*** ->
> > /tmp/**tmp**
> > -rw-rw-r-- 1 albinus albinus    0 Aug 20 10:00 /tmp/**tmp**
> >
> > And your patch makes the Tramp test suite fail. Try
> >
> > # make check
Sorry I should have do that first. But ... this won't work on my win7 computer 
(I think it's a problem between msys and emacs).


> >
> > The problem is, that in function `tramp--test-special-characters' the
> > file "*foo*bar*baz*" is checked. With your mask "**", the stat command
> > temporarily returns "***foo*bar*baz***", Tramp cannot decide safely,
> > which of the "**" characters has to be replaced in sed.
> >
> > So we would need another mask, which won't appear most likely in the
> > file name. Maybe you play with generating an arbitrary string, as
> > `tramp-end-of-heredoc' does?
> >
I've tried to figure how to add tests for link with // in path but without any 
success. Sorry.

> > Best regards, Michael.
Best regards Pierre

--8<---------------cut here---------------start------------->8---

1 file changed, 12 insertions(+), 12 deletions(-)
 lisp/tramp-sh.el | 24 ++++++++++++------------

modified   lisp/tramp-sh.el
@@ -1304,18 +1304,18 @@ target of the symlink differ."
     (concat
      ;; On Opsware, pdksh (which is the true name of ksh there)
      ;; doesn't parse correctly the sequence "((".  Therefore, we add
-     ;; a space.  Apostrophes in the stat output are masked as "//",
+     ;; a space.  Apostrophes in the stat output are masked as "\\0", (null 
char)
      ;; in order to make a proper shell escape of them in file names.
-     "( (%s %s || %s -h %s) && (%s -c "
-     "'((//%%N//) %%h %s %s %%Xe0 %%Ye0 %%Ze0 %%se0 //%%A// t %%ie0 -1)' "
-     "%s | sed -e 's/\"/\\\\\"/g' -e 's/\\/\\//\"/g') || echo nil)")
+     "( (%s %s || %s -h %s) && (%s --printf "
+     "'((\\0%%N\\0) %%h %s %s %%Xe0 %%Ye0 %%Ze0 %%se0 \\0%%A\\0 t %%ie0 
-1)\\n' "
+     "%s | sed -e 's/\"/\\\\\"/g' -e 's/\\o0/\"/g') || echo nil)")
     (tramp-get-file-exists-command vec)
     (tramp-shell-quote-argument localname)
     (tramp-get-test-command vec)
     (tramp-shell-quote-argument localname)
     (tramp-get-remote-stat vec)
-    (if (eq id-format 'integer) "%ue0" "//%U//")
-    (if (eq id-format 'integer) "%ge0" "//%G//")
+    (if (eq id-format 'integer) "%ue0" "\\0%U\\0")
+    (if (eq id-format 'integer) "%ge0" "\\0%G\\0")
     (tramp-shell-quote-argument localname))))
 
 (defun tramp-sh-handle-set-visited-file-modtime (&optional time-list)
@@ -1747,12 +1747,12 @@ be non-negative integers."
      ;; We must care about file names with spaces, or starting with
      ;; "-"; this would confuse xargs.  "ls -aQ" might be a solution,
      ;; but it does not work on all remote systems.  Apostrophes in
-     ;; the stat output are masked as "//", in order to make a proper
+     ;; the stat output are masked as "\\0" (null char), in order to make a 
proper
      ;; shell escape of them in file names.
      "cd %s && echo \"(\"; (%s %s -a | "
-     "xargs %s -c "
-     "'(//%%n// (//%%N//) %%h %s %s %%Xe0 %%Ye0 %%Ze0 %%se0 //%%A// t %%ie0 
-1)' "
-     "-- 2>/dev/null | sed -e 's/\"/\\\\\"/g' -e 's/\\/\\//\"/g'); echo 
\")\"")
+     "xargs %s -printf "
+     "'(\\0%%n\\0 (\\0%%N\\0) %%h %s %s %%Xe0 %%Ye0 %%Ze0 %%se0 \\0%%A\\0 t 
%%ie0 -1)' "
+     "-- 2>/dev/null | sed -e 's/\"/\\\\\"/g' -e 's/\\o0/\"/g' ); echo 
\")\"")
     (tramp-shell-quote-argument localname)
     (tramp-get-ls-command vec)
     ;; On systems which have no quoting style, file names with
@@ -1760,8 +1760,8 @@ be non-negative integers."
     (if (tramp-get-ls-command-with-quoting-style vec)
        "--quoting-style=shell" "")
     (tramp-get-remote-stat vec)
-    (if (eq id-format 'integer) "%ue0" "//%U//")
-    (if (eq id-format 'integer) "%ge0" "//%G//"))))
+    (if (eq id-format 'integer) "%ue0" "\\0%U\\0")
+    (if (eq id-format 'integer) "%ge0" "\\0%G\\0"))))
 
 ;; This function should return "foo/" for directories and "bar" for
 ;; files.


--8<---------------cut here---------------end--------------->8---