[Emacs-diffs] emacs/lisp/net tramp.el

[Michael Albinus]

CVSROOT:        /sources/emacs
Module name:    emacs
Changes by:     Michael Albinus <albinus>       09/10/26 09:29:01

Modified files:
        lisp/net       : tramp.el 

Log message:
        * net/tramp.el (tramp-perl-file-truename): New defconst.  Perl
        code contributed by yary <address@hidden> (tiny change).
        (tramp-handle-file-truename, tramp-get-remote-perl): Use it.
        Check also for "perl-file-spec" and "perl-cwd-realpath"
        properties.
        (tramp-handle-write-region): In case of APPEND, reuse the tmpfile
        name.
        
        * net/tramp.el (tramp-perl-file-name-all-completions): New
        defconst.
        (tramp-get-remote-readlink): New defun.
        (tramp-handle-file-truename): Use it.
        (tramp-handle-file-exists-p): Check file-attributes cache, assume
        file exists if cache value present.
        (tramp-check-cached-permissions) New defun.
        (tramp-handle-file-readable-p): Use it.
        (tramp-handle-file-writable-p): Likewise.
        (tramp-handle-file-executable-p): Likewise.
        (tramp-handle-file-name-all-completions): Try using Perl to get
        partial completions.  When perl not available, combine `cd' and
        `ls' into single remote operation and use shell expansion to get
        partial remote directory contents.  Set `file-exists-p' cache for
        directory and any files returned by ls.  Change cache handling to
        support partial directory contents.  Use error message emitted by
        remote `cd' or Perl code for local tramp-error.
        (tramp-do-copy-or-rename-file-directly): Avoid separate
        tramp-send-command-and-check call.
        (tramp-handle-process-file): Merge three remote ops into one.  Do
        not flush all caches when `process-file-side-effects' is set.
        (tramp-handle-write-region): Avoid tramp-set-file-uid-gid if
        file-attributes shows uid/gid to be set already.

CVSWeb URLs:
http://cvs.savannah.gnu.org/viewcvs/emacs/lisp/net/tramp.el?cvsroot=emacs&r1=1.263&r2=1.264

Patches:
Index: tramp.el
===================================================================
RCS file: /sources/emacs/emacs/lisp/net/tramp.el,v
retrieving revision 1.263
retrieving revision 1.264
diff -u -b -r1.263 -r1.264
--- tramp.el    23 Oct 2009 15:04:08 -0000      1.263
+++ tramp.el    26 Oct 2009 09:29:00 -0000      1.264
@@ -1613,6 +1613,75 @@
 for this or `uudecode -p', but some systems don't, and for them
 we have this shell function.")
 
+(defconst tramp-perl-file-truename
+  "%s -e '
+use File::Spec;
+use Cwd \"realpath\";
+
+sub recursive {
+    my ($volume, @dirs) = @_;
+    my $real = realpath(File::Spec->catpath(
+                   $volume, File::Spec->catdir(@dirs), \"\"));
+    if ($real) {
+        my ($vol, $dir) = File::Spec->splitpath($real, 1);
+        return ($vol, File::Spec->splitdir($dir));
+    }
+    else {
+        my $last = pop(@dirs);
+        ($volume, @dirs) = recursive($volume, @dirs);
+        push(@dirs, $last);
+        return ($volume, @dirs);
+    }
+}
+
+$result = realpath($ARGV[0]);
+if (!$result) {
+    my ($vol, $dir) = File::Spec->splitpath($ARGV[0], 1);
+    ($vol, @dirs) = recursive($vol, File::Spec->splitdir($dir));
+
+    $result = File::Spec->catpath($vol, File::Spec->catdir(@dirs), \"\");
+}
+
+if ($ARGV[0] =~ /\\/$/) {
+    $result = $result . \"/\";
+}
+
+print \"\\\"$result\\\"\\n\";
+' \"$1\" 2>/dev/null"
+  "Perl script to produce output suitable for use with `file-truename'
+on the remote file system.
+Escape sequence %s is replaced with name of Perl binary.
+This string is passed to `format', so percent characters need to be doubled.")
+
+(defconst tramp-perl-file-name-all-completions
+  "%s -e 'sub case {
+ my $str = shift;
+ if ($ARGV[2]) {
+  return lc($str);
+ }
+ else {
+  return $str;
+ }
+}
+opendir(d, $ARGV[0]) || die(\"$ARGV[0]: $!\\nfail\\n\");
address@hidden = readdir(d); closedir(d);
+foreach $f (@files) {
+ if (case(substr($f, 0, length($ARGV[1]))) eq case($ARGV[1])) {
+  if (-d \"$ARGV[0]/$f\") {
+   print \"$f/\\n\";
+  }
+  else {
+   print \"$f\\n\";
+  }
+ }
+}
+print \"ok\\n\"
+' \"$1\" \"$2\" \"$3\" 2>/dev/null"
+  "Perl script to produce output suitable for use with
+`file-name-all-completions' on the remote file system.  Escape
+sequence %s is replaced with name of Perl binary.  This string is
+passed to `format', so percent characters need to be doubled.")
+
 ;; Perl script to implement `file-attributes' in a Lisp `read'able
 ;; output.  If you are hacking on this, note that you get *no* output
 ;; unless this spits out a complete line, including the '\n' at the
@@ -2430,21 +2499,46 @@
   "Like `file-truename' for Tramp files."
   (with-parsed-tramp-file-name (expand-file-name filename) nil
     (with-file-property v localname "file-truename"
-      (let* ((directory-sep-char ?/) ; for XEmacs
+      (let ((result nil))                      ; result steps in reverse order
+       (tramp-message v 4 "Finding true name for `%s'" filename)
+       (cond
+        ;; Use GNU readlink --canonicalize-missing where available.
+        ((tramp-get-remote-readlink v)
+         (setq result
+               (tramp-send-command-and-read
+                v
+                (format "echo \"\\\"`%s --canonicalize-missing %s`\\\"\""
+                        (tramp-get-remote-readlink v)
+                        (tramp-shell-quote-argument localname)))))
+
+        ;; Use Perl implementation.
+        ((and (tramp-get-remote-perl v)
+              (tramp-get-connection-property v "perl-file-spec" nil)
+              (tramp-get-connection-property v "perl-cwd-realpath" nil))
+         (tramp-maybe-send-script
+          v tramp-perl-file-truename "tramp_perl_file_truename")
+         (setq result
+               (tramp-send-command-and-read
+                v
+                (format "tramp_perl_file_truename %s"
+                        (tramp-shell-quote-argument localname)))))
+
+        ;; Do it yourself.  We bind `directory-sep-char' here for
+        ;; XEmacs on Windows, which would otherwise use backslash.
+        (t (let* ((directory-sep-char ?/)
             (steps (tramp-compat-split-string localname "/"))
             (localnamedir (tramp-run-real-handler
                            'file-name-as-directory (list localname)))
             (is-dir (string= localname localnamedir))
             (thisstep nil)
             (numchase 0)
-            ;; Don't make the following value larger than necessary.
-            ;; People expect an error message in a timely fashion when
-            ;; something is wrong; otherwise they might think that Emacs
-            ;; is hung.  Of course, correctness has to come first.
+                  ;; Don't make the following value larger than
+                  ;; necessary.  People expect an error message in a
+                  ;; timely fashion when something is wrong;
+                  ;; otherwise they might think that Emacs is hung.
+                  ;; Of course, correctness has to come first.
             (numchase-limit 20)
-            (result nil)                       ;result steps in reverse order
             symlink-target)
-       (tramp-message v 4 "Finding true name for `%s'" filename)
        (while (and steps (< numchase numchase-limit))
          (setq thisstep (pop steps))
          (tramp-message
@@ -2482,7 +2576,8 @@
                      "Symlink target `%s' on wrong host" symlink-target))
                   (setq symlink-target localname))
                 (setq steps
-                      (append (tramp-compat-split-string symlink-target "/")
+                            (append (tramp-compat-split-string
+                                     symlink-target "/")
                               steps)))
                (t
                 ;; It's a file.
@@ -2499,7 +2594,8 @@
                "/"))
        (when (and is-dir (or (string= "" result)
                              (not (string= (substring result -1) "/"))))
-         (setq result (concat result "/")))
+               (setq result (concat result "/"))))))
+
        (tramp-message v 4 "True name of `%s' is `%s'" filename result)
        (tramp-make-tramp-file-name method user host result)))))
 
@@ -2509,12 +2605,16 @@
   "Like `file-exists-p' for Tramp files."
   (with-parsed-tramp-file-name filename nil
     (with-file-property v localname "file-exists-p"
+      (or (not (null (tramp-get-file-property
+                      v localname "file-attributes-integer" nil)))
+          (not (null (tramp-get-file-property
+                      v localname "file-attributes-string" nil)))
       (zerop (tramp-send-command-and-check
              v
              (format
               "%s %s"
               (tramp-get-file-exists-command v)
-              (tramp-shell-quote-argument localname)))))))
+                   (tramp-shell-quote-argument localname))))))))
 
 ;; Inodes don't exist for some file systems.  Therefore we must
 ;; generate virtual ones.  Used in `find-buffer-visiting'.  The method
@@ -2843,13 +2943,19 @@
   "Like `file-executable-p' for Tramp files."
   (with-parsed-tramp-file-name filename nil
     (with-file-property v localname "file-executable-p"
-      (zerop (tramp-run-test "-x" filename)))))
+      ;; Examine `file-attributes' cache to see if request can be
+      ;; satisfied without remote operation.
+      (or (tramp-check-cached-permissions v ?x)
+          (zerop (tramp-run-test "-x" filename))))))
 
 (defun tramp-handle-file-readable-p (filename)
   "Like `file-readable-p' for Tramp files."
   (with-parsed-tramp-file-name filename nil
     (with-file-property v localname "file-readable-p"
-      (zerop (tramp-run-test "-r" filename)))))
+      ;; Examine `file-attributes' cache to see if request can be
+      ;; satisfied without remote operation.
+      (or (tramp-check-cached-permissions v ?r)
+          (zerop (tramp-run-test "-r" filename))))))
 
 ;; When the remote shell is started, it looks for a shell which groks
 ;; tilde expansion.  Here, we assume that all shells which grok tilde
@@ -2939,8 +3045,10 @@
   (with-parsed-tramp-file-name filename nil
     (with-file-property v localname "file-writable-p"
       (if (file-exists-p filename)
-         ;; Existing files must be writable.
-         (zerop (tramp-run-test "-w" filename))
+         ;; Examine `file-attributes' cache to see if request can be
+         ;; satisfied without remote operation.
+          (or (tramp-check-cached-permissions v ?w)
+              (zerop (tramp-run-test "-w" filename)))
        ;; If file doesn't exist, check if directory is writable.
        (and (zerop (tramp-run-test
                     "-d" (file-name-directory filename)))
@@ -3074,50 +3182,149 @@
   "Like `file-name-all-completions' for Tramp files."
   (unless (save-match-data (string-match "/" filename))
     (with-parsed-tramp-file-name (expand-file-name directory) nil
-      ;; Flush the directory cache.  There could be changed directory
-      ;; contents.
-      (when (and (integerp tramp-completion-reread-directory-timeout)
-                (> (tramp-time-diff
+
+      (all-completions
+       filename
+       (mapcar
+       'list
+        (or
+         ;; Try cache first
+         (and
+          ;; Ignore if expired
+          (or (not (integerp tramp-completion-reread-directory-timeout))
+              (<= (tramp-time-diff
                     (current-time)
                     (tramp-get-file-property
                      v localname "last-completion" '(0 0 0)))
                    tramp-completion-reread-directory-timeout))
-       (tramp-flush-file-property v localname))
 
-      (all-completions
-       filename
+          ;; Try cache entries for filename, filename with last
+          ;; character removed, filename with last two characters
+          ;; removed, ..., and finally the empty string - all
+          ;; concatenated to the local directory name
+
+          ;; This is inefficient for very long filenames, pity
+          ;; `reduce' is not available...
+          (car
+           (apply
+            'append
        (mapcar
-       'list
-       (with-file-property v localname "file-name-all-completions"
-         (let (result)
-          (tramp-barf-unless-okay
+             (lambda (x)
+               (let ((cache-hit
+                      (tramp-get-file-property
            v
-           (format "cd %s" (tramp-shell-quote-argument localname))
-           "tramp-handle-file-name-all-completions: Couldn't `cd %s'"
-           (tramp-shell-quote-argument localname))
+                       (concat localname (substring filename 0 x))
+                       "file-name-all-completions"
+                       nil)))
+                 (when cache-hit (list cache-hit))))
+             (tramp-compat-number-sequence (length filename) 0 -1)))))
 
+         ;; Cache expired or no matching cache entry found so we need
+         ;; to perform a remote operation
+         (let (result)
           ;; Get a list of directories and files, including reliably
           ;; tagging the directories with a trailing '/'.  Because I
           ;; rock.  address@hidden
+
+           ;; Changed to perform `cd' in the same remote op and only
+           ;; get entries starting with `filename'. Capture any `cd'
+           ;; error messages.  Ensure any `cd' and `echo' aliases are
+           ;; ignored.
           (tramp-send-command
            v
-           (format (concat "%s -a 2>/dev/null | while read f; do "
-                           "if %s -d \"$f\" 2>/dev/null; "
-                           "then echo \"$f/\"; else echo \"$f\"; fi; done")
+            (if (tramp-get-remote-perl v)
+                (progn
+                  (tramp-maybe-send-script
+                   v tramp-perl-file-name-all-completions
+                   "tramp_perl_file_name_all_completions")
+                  (format "tramp_perl_file_name_all_completions %s %s %d"
+                          (tramp-shell-quote-argument localname)
+                          (tramp-shell-quote-argument filename)
+                          (if (symbol-value
+                              'read-file-name-completion-ignore-case)
+                             1 0)))
+
+              (format (concat
+                       "(\\cd %s 2>&1 && (%s %s -a 2>/dev/null"
+                       ;; `ls' with wildcard might fail with `Argument
+                       ;; list too long' error in some corner cases; if
+                       ;; `ls' fails after `cd' succeeded, chances are
+                       ;; that's the case, so let's retry without
+                       ;; wildcard.  This will return "too many" entries
+                       ;; but that isn't harmful.
+                       " || %s -a 2>/dev/null)"
+                       " | while read f; do"
+                       " if %s -d \"$f\" 2>/dev/null;"
+                       " then \\echo \"$f/\"; else \\echo \"$f\"; fi; done"
+                       " && \\echo ok) || \\echo fail")
+                      (tramp-shell-quote-argument localname)
+                      (tramp-get-ls-command v)
+                      ;; When `filename' is empty, just `ls' without
+                      ;; filename argument is more efficient than `ls *'
+                      ;; for very large directories and might avoid the
+                      ;; `Argument list too long' error.
+                      ;;
+                      ;; With and only with wildcard, we need to add
+                      ;; `-d' to prevent `ls' from descending into
+                      ;; sub-directories.
+                      (if (zerop (length filename))
+                          "."
+                        (concat (tramp-shell-quote-argument filename) "* -d"))
                    (tramp-get-ls-command v)
-                   (tramp-get-test-command v)))
+                      (tramp-get-test-command v))))
 
           ;; Now grab the output.
           (with-current-buffer (tramp-get-buffer v)
             (goto-char (point-max))
+
+             ;; Check result code, found in last line of output
+             (forward-line -1)
+             (if (looking-at "^fail$")
+                 (progn
+                   ;; Grab error message from line before last line
+                   ;; (it was put there by `cd 2>&1')
+                   (forward-line -1)
+                   (tramp-error
+                    v 'file-error
+                    "tramp-handle-file-name-all-completions: %s"
+                    (buffer-substring
+                     (point) (tramp-compat-line-end-position))))
+               ;; For peace of mind, if buffer doesn't end in `fail'
+               ;; then it should end in `ok'.  If neither are in the
+               ;; buffer something went seriously wrong on the remote
+               ;; side.
+               (unless (looking-at "^ok$")
+                 (tramp-error
+                  v 'file-error
+                  "\
+tramp-handle-file-name-all-completions: internal error accessing `%s': `%s'"
+                  (tramp-shell-quote-argument localname) (buffer-string))))
+
             (while (zerop (forward-line -1))
               (push (buffer-substring
                      (point) (tramp-compat-line-end-position))
                     result)))
 
+           ;; Because the remote op went through OK we know the
+           ;; directory we `cd'-ed to exists
+           (tramp-set-file-property
+            v localname "file-exists-p" t)
+
+           ;; Because the remote op went through OK we know every
+           ;; file listed by `ls' exists.
+           (mapc (lambda (entry)
+                  (tramp-set-file-property
+                   v (concat localname entry) "file-exists-p" t))
+                result)
+
           (tramp-set-file-property
            v localname "last-completion" (current-time))
-          result)))))))
+
+           ;; Store result in the cache
+           (tramp-set-file-property
+            v (concat localname filename)
+            "file-name-all-completions"
+            result))))))))
 
 ;; The following isn't needed for Emacs 20 but for 19.34?
 (defun tramp-handle-file-name-completion
@@ -3380,16 +3587,18 @@
              (if t1 (tramp-handle-file-remote-p filename 'localname) filename))
             (localname2
              (if t2 (tramp-handle-file-remote-p newname 'localname) newname))
-            (prefix (file-remote-p (if t1 filename newname))))
+            (prefix (file-remote-p (if t1 filename newname)))
+             cmd-result)
 
        (cond
         ;; Both files are on a remote host, with same user.
         ((and t1 t2)
-         (tramp-send-command
+          (setq cmd-result
+                (tramp-send-command-and-check
           v
           (format "%s %s %s" cmd
                   (tramp-shell-quote-argument localname1)
-                  (tramp-shell-quote-argument localname2)))
+                         (tramp-shell-quote-argument localname2))))
          (with-current-buffer (tramp-get-buffer v)
            (goto-char (point-min))
            (unless
@@ -3398,7 +3607,7 @@
                      ;; Mask cp -f error.
                      (re-search-forward
                       tramp-operation-not-permitted-regexp nil t))
-                (zerop (tramp-send-command-and-check v nil)))
+                (zerop cmd-result))
              (tramp-error-with-buffer
               nil v 'file-error
               "Copying directly failed, see buffer `%s' for details."
@@ -4128,20 +4337,20 @@
        (setq outbuf (current-buffer))))
       (when stderr (setq command (format "%s 2>%s" command stderr)))
 
-      ;; Goto working directory.
-      (tramp-send-command
-       v (format "cd %s" (tramp-shell-quote-argument localname)))
       ;; Send the command.  It might not return in time, so we protect it.
       (condition-case nil
          (unwind-protect
-             (tramp-send-command v command)
+              (setq ret
+                    (tramp-send-command-and-check
+                     v (format "\\cd %s; %s"
+                               (tramp-shell-quote-argument localname)
+                               command)))
            ;; We should show the output anyway.
            (when outbuf
-             (let ((output-string
-                    (with-current-buffer (tramp-get-connection-buffer v)
-                      (buffer-substring (point-min) (point-max)))))
                (with-current-buffer outbuf
-                 (insert output-string)))
+                (insert
+                 (with-current-buffer (tramp-get-connection-buffer v)
+                   (buffer-string))))
              (when display (display-buffer outbuf))))
        ;; When the user did interrupt, we should do it also.  We use
        ;; return code -1 as marker.
@@ -4153,8 +4362,6 @@
         (kill-buffer (tramp-get-connection-buffer v))
         (setq ret 1)))
 
-      ;; Check return code.
-      (unless ret (setq ret (tramp-send-command-and-check v nil)))
       ;; Provide error file.
       (when tmpstderr (rename-file tmpstderr (cadr destination) t))
 
@@ -4672,13 +4879,13 @@
              ;; Write region into a tmp file.  This isn't really
              ;; needed if we use an encoding function, but currently
              ;; we use it always because this makes the logic
-             ;; simpler.  If `append' is non-nil, we copy the file
-             ;; locally, and let the native `write-region'
-             ;; implementation do the job.
-             (tmpfile (if append
-                          (file-local-copy filename)
-                        (or tramp-temp-buffer-file-name
-                            (tramp-compat-make-temp-file filename)))))
+             ;; simpler.
+             (tmpfile (or tramp-temp-buffer-file-name
+                          (tramp-compat-make-temp-file filename))))
+
+         ;; If `append' is non-nil, we copy the file locally, and let
+         ;; the native `write-region' implementation do the job.
+         (when append (copy-file filename tmpfile 'ok))
 
          ;; We say `no-message' here because we don't want the
          ;; visited file modtime data to be clobbered from the temp
@@ -4836,17 +5043,22 @@
 
       ;; We must protect `last-coding-system-used', now we have set it
       ;; to its correct value.
-      (let (last-coding-system-used)
+      (let (last-coding-system-used (need-chown t))
        ;; Set file modification time.
        (when (or (eq visit t) (stringp visit))
+          (let ((file-attr (file-attributes filename)))
          (set-visited-file-modtime
           ;; We must pass modtime explicitely, because filename can
           ;; be different from (buffer-file-name), f.e. if
           ;; `file-precious-flag' is set.
-          (nth 5 (file-attributes filename))))
+             (nth 5 file-attr))
+            (when (and (eq (nth 2 file-attr) uid)
+                       (eq (nth 3 file-attr) gid))
+              (setq need-chown nil))))
 
        ;; Set the ownership.
-       (tramp-set-file-uid-gid filename uid gid)
+        (when need-chown
+          (tramp-set-file-uid-gid filename uid gid))
        (when (or (eq visit t) (null visit) (stringp visit))
          (tramp-message v 0 "Wrote %s" filename))
        (run-hooks 'tramp-handle-write-region-hook)))))
@@ -7244,6 +7456,49 @@
             (tramp-get-device vec))
     attr))
 
+(defun tramp-check-cached-permissions (vec access)
+  "Check `file-attributes' caches for VEC.
+Return t if according to the cache access type ACCESS is known to
+be granted."
+  (let ((result nil)
+        (offset (cond
+                 ((eq ?r access) 1)
+                 ((eq ?w access) 2)
+                 ((eq ?x access) 3))))
+    (dolist (suffix '("string" "integer") result)
+      (setq
+       result
+       (or
+        result
+        (let ((file-attr
+               (tramp-get-file-property
+                vec (tramp-file-name-localname vec)
+                (concat "file-attributes-" suffix) nil))
+              (remote-uid
+               (tramp-get-connection-property
+                vec (concat "uid-" suffix) nil))
+              (remote-gid
+               (tramp-get-connection-property
+                vec (concat "gid-" suffix) nil)))
+          (and
+           file-attr
+           (or
+            ;; Not a symlink
+            (eq t (car file-attr))
+            (null (car file-attr)))
+           (or
+            ;; World accessible.
+            (eq access (aref (nth 8 file-attr) (+ offset 6)))
+            ;; User accessible and owned by user.
+            (and
+             (eq access (aref (nth 8 file-attr) offset))
+             (equal remote-uid (nth 2 file-attr)))
+            ;; Group accessible and owned by user's
+            ;; principal group.
+            (and
+             (eq access (aref (nth 8 file-attr) (+ offset 3)))
+             (equal remote-gid (nth 3 file-attr)))))))))))
+
 (defun tramp-get-inode (vec)
   "Returns the virtual inode number.
 If it doesn't exist, generate a new one."
@@ -7707,8 +7962,21 @@
 (defun tramp-get-remote-perl (vec)
   (with-connection-property vec "perl"
     (tramp-message vec 5 "Finding a suitable `perl' command")
+    (let ((result
     (or (tramp-find-executable vec "perl5" (tramp-get-remote-path vec))
-       (tramp-find-executable vec "perl" (tramp-get-remote-path vec)))))
+              (tramp-find-executable
+               vec "perl" (tramp-get-remote-path vec)))))
+      ;; We must check also for some Perl modules.
+      (when result
+       (with-connection-property vec "perl-file-spec"
+         (zerop
+          (tramp-send-command-and-check
+           vec (format "%s -e 'use File::Spec;'" result))))
+       (with-connection-property vec "perl-cwd-realpath"
+         (zerop
+          (tramp-send-command-and-check
+           vec (format "%s -e 'use Cwd \"realpath\";'" result)))))
+      result)))
 
 (defun tramp-get-remote-stat (vec)
   (with-connection-property vec "stat"
@@ -7732,6 +8000,21 @@
          (setq result nil)))
       result)))
 
+(defun tramp-get-remote-readlink (vec)
+  (with-connection-property vec "readlink"
+    (tramp-message vec 5 "Finding a suitable `readlink' command")
+    (let ((result (tramp-find-executable
+                  vec "readlink" (tramp-get-remote-path vec))))
+      (when (and result
+                ;; We don't want to display an error message.
+                (with-temp-message (or (current-message) "")
+                  (condition-case nil
+                      (zerop
+                       (tramp-send-command-and-check
+                        vec (format "%s --canonicalize-missing /" result)))
+                    (error nil))))
+       result))))
+
 (defun tramp-get-remote-id (vec)
   (with-connection-property vec "id"
     (tramp-message vec 5 "Finding POSIX `id' command")