Tramp code cleanup

* lisp/net/tramp-sh.el (tramp-methods) <telnet, nc>:
Reintroduce "%n" marker.
(tramp-maybe-open-connection): Handle it.

* lisp/net/tramp.el (tramp-prefix-regexp):
* lisp/net/tramp-smb.el (tramp-smb-options): Fix docstring.

* lisp/net/tramp*.el: Fix typos.  Remove trailing space from
`yes-or-no-p' and `y-or-n-p' prompts.

* test/lisp/net/tramp-tests.el (tramp--test-telnet-p): New defun.
(tramp-test29-start-file-process, tramp-test30-make-process)
(tramp-test35-remote-path, tramp-test44-asynchronous-requests):
Adapt tests.

lisp/net/tramp-adb.el

@@ -361,7 +361,7 @@ arguments to pass to the OPERATION."
     (tramp-message vec 5 "Finding a suitable `ls' command")
     (cond
      ;; Support Android derived systems where "ls" command is provided
-     ;; by GNU Coreutils. Force "ls" to print one column and set
+     ;; by GNU Coreutils.  Force "ls" to print one column and set
      ;; time-style to imitate other "ls" flavors.
      ((tramp-adb-send-command-and-check
        vec (concat "ls --time-style=long-iso "
@@ -548,7 +548,7 @@ But handle the case, if the \"test\" command is not available."
 	       (or (eq mustbenew 'excl)
 		   (not
 		    (y-or-n-p
-		     (format "File %s exists; overwrite anyway? " filename)))))
+		     (format "File %s exists; overwrite anyway?" filename)))))
       (tramp-error v 'file-already-exists filename))
 
     (let ((file-locked (eq (file-locked-p lockname) t))

lisp/net/tramp-archive.el

@@ -190,7 +190,7 @@ It must be supported by libarchive(3).")
 
 ;; In older Emacsen (prior 27.1), `tramp-archive-autoload-file-name-regexp'
 ;; is not autoloaded.  So we cannot expect it to be known in
-;; tramp-loaddefs.el. But it exists, when tramp-archive.el is loaded.
+;; tramp-loaddefs.el.  But it exists, when tramp-archive.el is loaded.
 ;;;###tramp-autoload
 (defconst tramp-archive-file-name-regexp
   (ignore-errors (tramp-archive-autoload-file-name-regexp))

lisp/net/tramp-cmds.el

@@ -312,7 +312,7 @@ The remote connection identified by SOURCE is flushed by
      (if (null connections)
 	 (tramp-user-error nil "There are no remote connections.")
        (setq source
-	     ;; Likely, the source remote connection is broken. So we
+	     ;; Likely, the source remote connection is broken.  So we
 	     ;; shall avoid any action on it.
 	     (let (non-essential)
 	       (completing-read-default
@@ -717,7 +717,7 @@ the debug buffer(s).")
 	(setq buffer-read-only t)
 	(goto-char (point-min))
 
-	(when (y-or-n-p "Do you want to append the buffer(s)? ")
+	(when (y-or-n-p "Do you want to append the buffer(s)?")
 	  ;; OK, let's send.  First we delete the buffer list.
 	  (kill-buffer nil)
 	  (switch-to-buffer curbuf)

lisp/net/tramp-crypt.el

@@ -517,7 +517,7 @@ kept in their encrypted form."
 	      tramp-crypt-encfs-config
 	      (directory-files name nil directory-files-no-dot-files-regexp))
 	     (yes-or-no-p
-	      "There exist encrypted files, do you want to continue? "))
+	      "There exist encrypted files, do you want to continue?"))
     (setq tramp-crypt-directories (delete name tramp-crypt-directories))
     (tramp-register-file-name-handlers)))
 

lisp/net/tramp-ftp.el

@@ -120,15 +120,15 @@ pass to the OPERATION."
 		 (nth 2 tramp-file-name-structure)
 		 (nth 4 tramp-file-name-structure)))
 	  ;; ange-ftp uses `ange-ftp-ftp-name-arg' and `ange-ftp-ftp-name-res'
-	  ;; for optimization in `ange-ftp-ftp-name'. If Tramp wasn't active,
+	  ;; for optimization in `ange-ftp-ftp-name'.  If Tramp wasn't active,
 	  ;; there could be incorrect values from previous calls in case the
-	  ;; "ftp" method is used in the Tramp file name. So we unset
+	  ;; "ftp" method is used in the Tramp file name.  So we unset
 	  ;; those values.
 	  (ange-ftp-ftp-name-arg "")
 	  (ange-ftp-ftp-name-res nil))
       (cond
        ;; If argument is a symlink, `file-directory-p' and
-       ;; `file-exists-p' call the traversed file recursively. So we
+       ;; `file-exists-p' call the traversed file recursively.  So we
        ;; cannot disable the file-name-handler this case.  We set the
        ;; connection property "started" in order to put the remote
        ;; location into the cache, which is helpful for further

lisp/net/tramp-gvfs.el

@@ -1815,10 +1815,8 @@ a downcased host name only."
 			     (message "%s" message)
 			   (pop-to-buffer (current-buffer)))
 			 (if (yes-or-no-p
-			      (concat
+			      (buffer-substring
-			       (buffer-substring
+			       (line-beginning-position) (point)))
-				(line-beginning-position) (point))
-			       " "))
 			     0 1)))))
 
 		;; When QUIT is raised, we shall return this
@@ -1840,7 +1838,7 @@ a downcased host name only."
   (ignore-errors
     (let ((signal-name (dbus-event-member-name last-input-event))
 	  (elt mount-info))
-      ;; Jump over the first elements of the mount info. Since there
+      ;; Jump over the first elements of the mount info.  Since there
       ;; were changes in the entries, we cannot access dedicated
       ;; elements.
       (while (stringp (car elt)) (setq elt (cdr elt)))
@@ -1936,7 +1934,7 @@ a downcased host name only."
 	      :session tramp-gvfs-service-daemon tramp-gvfs-path-mounttracker
 	      tramp-gvfs-interface-mounttracker tramp-gvfs-listmounts))
 	  nil)
-       ;; Jump over the first elements of the mount info. Since there
+       ;; Jump over the first elements of the mount info.  Since there
        ;; were changes in the entries, we cannot access dedicated
        ;; elements.
        (while (stringp (car elt)) (setq elt (cdr elt)))

lisp/net/tramp-sh.el

@@ -244,14 +244,14 @@ The string is used in `tramp-methods'.")
  (add-to-list 'tramp-methods
               `("telnet"
                 (tramp-login-program        "telnet")
-                (tramp-login-args           (("%h") ("%p")))
+                (tramp-login-args           (("%h") ("%p") ("%n")))
                 (tramp-remote-shell         ,tramp-default-remote-shell)
                 (tramp-remote-shell-login   ("-l"))
                 (tramp-remote-shell-args    ("-c"))))
  (add-to-list 'tramp-methods
               `("nc"
                 (tramp-login-program        "telnet")
-                (tramp-login-args           (("%h") ("%p")))
+                (tramp-login-args           (("%h") ("%p") ("%n")))
                 (tramp-remote-shell         ,tramp-default-remote-shell)
                 (tramp-remote-shell-login   ("-l"))
                 (tramp-remote-shell-args    ("-c"))
@@ -1064,7 +1064,7 @@ component is used as the target of the symlink."
 			 (not
 			  (yes-or-no-p
 			   (format
-			    "File %s already exists; make it a link anyway? "
+			    "File %s already exists; make it a link anyway?"
 			    localname)))))
 		(tramp-error v 'file-already-exists localname)
 	      (delete-file linkname)))
@@ -1073,7 +1073,7 @@ component is used as the target of the symlink."
 
 	  ;; Right, they are on the same host, regardless of user,
 	  ;; method, etc.  We now make the link on the remote
-	  ;; machine. This will occur as the user that TARGET belongs to.
+	  ;; machine.  This will occur as the user that TARGET belongs to.
 	  (and (tramp-send-command-and-check
 		v (format "cd %s" (tramp-shell-quote-argument cwd)))
                (tramp-send-command-and-check
@@ -1825,7 +1825,7 @@ ID-FORMAT valid values are `string' and `integer'."
 		  (and (numberp ok-if-already-exists)
 		       (not (yes-or-no-p
 			     (format
-			      "File %s already exists; make it a link anyway? "
+			      "File %s already exists; make it a link anyway?"
 			      v2-localname)))))
 	      (tramp-error v2 'file-already-exists newname)
 	    (delete-file newname)))
@@ -2231,7 +2231,7 @@ the uid and gid from FILENAME."
 		;; Save exit.
 		(ignore-errors (delete-file tmpfile)))))))))
 
-      ;; Set the time and mode. Mask possible errors.
+      ;; Set the time and mode.  Mask possible errors.
       (ignore-errors
 	  (when keep-date
 	    (tramp-compat-set-file-times
@@ -2748,7 +2748,7 @@ the result will be a local, non-Tramp, file name."
 
 ;;; Remote commands:
 
-;; We use BUFFER also as connection buffer during setup. Because of
+;; We use BUFFER also as connection buffer during setup.  Because of
 ;; this, its original contents must be saved, and restored once
 ;; connection has been setup.
 (defun tramp-sh-handle-make-process (&rest args)
@@ -3269,7 +3269,7 @@ implementation will be used."
 	       (or (eq mustbenew 'excl)
 		   (not
 		    (y-or-n-p
-		     (format "File %s exists; overwrite anyway? " filename)))))
+		     (format "File %s exists; overwrite anyway?" filename)))))
       (tramp-error v 'file-already-exists filename))
 
     (let ((file-locked (eq (file-locked-p lockname) t))
@@ -4000,7 +4000,7 @@ Returns the absolute file name of PROGNAME, if found, and nil otherwise.
 This function expects to be in the right *tramp* buffer."
   (with-current-buffer (tramp-get-connection-buffer vec)
     (let (result)
-      ;; Check whether the executable is in $PATH. "which(1)" does not
+      ;; Check whether the executable is in $PATH.  "which(1)" does not
       ;; report always a correct error code; therefore we check the
       ;; number of words it returns.  "SunOS 5.10" (and maybe "SunOS
       ;; 5.11") have problems with this command, we disable the call
@@ -4904,6 +4904,8 @@ connection if a previous connection has died for some reason."
                 (tramp-error vec 'file-error "`tramp-encoding-shell' not set"))
 	      (let* ((current-host tramp-system-name)
 		     (target-alist (tramp-compute-multi-hops vec))
+		     ;; Needed for `tramp-get-remote-null-device'.
+		     (previous-hop nil)
 		     ;; We will apply `tramp-ssh-controlmaster-options'
 		     ;; only for the first hop.
 		     (options (tramp-ssh-controlmaster-options vec))
@@ -5016,6 +5018,8 @@ connection if a previous connection has died for some reason."
 			hop 'tramp-login-args
 			?h (or l-host "") ?u (or l-user "") ?p (or l-port "")
 			?c (format-spec options (format-spec-make ?t tmpfile))
+			?n (concat
+			    "2>" (tramp-get-remote-null-device previous-hop))
 			?l (concat remote-shell " " extra-args " -i"))
 		       ;; A restricted shell does not allow "exec".
 		       (when r-shell '("&&" "exit" "||" "exit")))
@@ -5031,10 +5035,12 @@ connection if a previous connection has died for some reason."
 		     tramp-actions-before-shell
 		     (or connection-timeout tramp-connection-timeout))
 		    (tramp-message
-		     vec 3 "Found remote shell prompt on `%s'" l-host))
+		     vec 3 "Found remote shell prompt on `%s'" l-host)
-		  ;; Next hop.
+
-		  (setq options ""
+		    ;; Next hop.
-			target-alist (cdr target-alist)))
+		    (setq options ""
+			  target-alist (cdr target-alist)
+			  previous-hop hop)))
 
 		;; Activate session timeout.
 		(when (tramp-get-connection-property p "session-timeout" nil)

lisp/net/tramp-smb.el

@@ -48,7 +48,7 @@
                   ;; Another guess.  We might implement a better check later on.
                   (tramp-case-insensitive t)))))
 
-;; Add a default for `tramp-default-user-alist'. Rule: For the SMB method,
+;; Add a default for `tramp-default-user-alist'.  Rule: For the SMB method,
 ;; the anonymous user is chosen.
 ;;;###tramp-autoload
 (tramp--with-startup
@@ -83,7 +83,7 @@ call, letting the SMB client use the default one."
 They are added to the `tramp-smb-program' call via \"--option '...'\".
 
 For example, if the deprecated SMB1 protocol shall be used, add to
-this variable (\"client min protocol=NT1\") ."
+this variable \"client min protocol=NT1\"."
   :group 'tramp
   :type '(repeat string)
   :version "28.1")
@@ -376,7 +376,7 @@ arguments to pass to the OPERATION."
 		(and (numberp ok-if-already-exists)
 		     (not (yes-or-no-p
 			   (format
-			    "File %s already exists; make it a link anyway? "
+			    "File %s already exists; make it a link anyway?"
 			    v2-localname)))))
 	    (tramp-error v2 'file-already-exists newname)
 	  (delete-file newname)))
@@ -1247,7 +1247,7 @@ component is used as the target of the symlink."
 		  (and (numberp ok-if-already-exists)
 		       (not (yes-or-no-p
 			     (format
-			      "File %s already exists; make it a link anyway? "
+			      "File %s already exists; make it a link anyway?"
 			      localname)))))
 	      (tramp-error v 'file-already-exists localname)
 	    (delete-file linkname)))
@@ -1526,7 +1526,7 @@ component is used as the target of the symlink."
 	  (tramp-error
 	   v 'file-error "Error while changing file's mode %s" filename))))))
 
-;; We use BUFFER also as connection buffer during setup. Because of
+;; We use BUFFER also as connection buffer during setup.  Because of
 ;; this, its original contents must be saved, and restored once
 ;; connection has been setup.
 (defun tramp-smb-handle-start-file-process (name buffer program &rest args)
@@ -1603,7 +1603,7 @@ errors for shares like \"C$/\", which are common in Microsoft Windows."
 	       (or (eq mustbenew 'excl)
 		   (not
 		    (y-or-n-p
-		     (format "File %s exists; overwrite anyway? " filename)))))
+		     (format "File %s exists; overwrite anyway?" filename)))))
       (tramp-error v 'file-already-exists filename))
 
     (let ((file-locked (eq (file-locked-p lockname) t))
@@ -1703,7 +1703,7 @@ If VEC has no cifs capabilities, exchange \"/\" by \"\\\\\"."
 
       localname)))
 
-;; Share names of a host are cached. It is very unlikely that the
+;; Share names of a host are cached.  It is very unlikely that the
 ;; shares do change during connection.
 (defun tramp-smb-get-file-entries (directory)
   "Read entries which match DIRECTORY.
@@ -2200,5 +2200,7 @@ Removes smb prompt.  Returns nil if an error message has appeared."
 ;;
 ;; * Try to remove the inclusion of dummy "" directory.  Seems to be at
 ;;   several places, especially in `tramp-smb-handle-insert-directory'.
+;;
+;; * Keep a separate connection process per share.
 
 ;;; tramp-smb.el ends here

lisp/net/tramp-sshfs.el

@@ -292,7 +292,7 @@ arguments to pass to the OPERATION."
 	       (or (eq mustbenew 'excl)
 		   (not
 		    (y-or-n-p
-		     (format "File %s exists; overwrite anyway? " filename)))))
+		     (format "File %s exists; overwrite anyway?" filename)))))
       (tramp-error v 'file-already-exists filename))
 
     (let ((file-locked (eq (file-locked-p lockname) t)))

lisp/net/tramp-sudoedit.el

@@ -190,7 +190,7 @@ arguments to pass to the OPERATION."
 		  (and (numberp ok-if-already-exists)
 		       (not (yes-or-no-p
 			     (format
-			      "File %s already exists; make it a link anyway? "
+			      "File %s already exists; make it a link anyway?"
 			      v2-localname)))))
 	      (tramp-error v2 'file-already-exists newname)
 	    (delete-file newname)))
@@ -632,7 +632,7 @@ component is used as the target of the symlink."
 		       (not
 			(yes-or-no-p
 			 (format
-			  "File %s already exists; make it a link anyway? "
+			  "File %s already exists; make it a link anyway?"
 			  localname)))))
 	      (tramp-error v 'file-already-exists localname)
 	    (delete-file linkname)))

lisp/net/tramp.el

@@ -861,7 +861,7 @@ Used in `tramp-make-tramp-file-name'.")
 
 (defvar tramp-prefix-regexp nil ;Initialized when defining `tramp-syntax'!
   "Regexp matching the very beginning of Tramp file names.
-Should always start with \"^\". Derived from `tramp-prefix-format'.")
+Should always start with \"^\".  Derived from `tramp-prefix-format'.")
 
 (defconst tramp-method-regexp-alist
   '((default    . "[[:alnum:]-]+")
@@ -2379,7 +2379,7 @@ For definition of that list see `tramp-set-completion-function'."
 
 ;; Inodes don't exist for some file systems.  Therefore we must
 ;; generate virtual ones.  Used in `find-buffer-visiting'.  The method
-;; applied might be not so efficient (Ange-FTP uses hashes). But
+;; applied might be not so efficient (Ange-FTP uses hashes).  But
 ;; performance isn't the major issue given that file transfer will
 ;; take time.
 (defvar tramp-inodes 0
@@ -2908,7 +2908,7 @@ not in completion mode."
 ;; I misuse a little bit the `tramp-file-name' structure in order to
 ;; handle completion possibilities for partial methods / user names /
 ;; host names.  Return value is a list of `tramp-file-name' structures
-;; according to possible completions. If "localname" is non-nil it
+;; according to possible completions.  If "localname" is non-nil it
 ;; means there shouldn't be a completion anymore.
 
 ;; Expected results:
@@ -3288,7 +3288,7 @@ User is always nil."
 	      (and (numberp ok-if-already-exists)
 		   (not (yes-or-no-p
 			 (format
-			  "File %s already exists; make it a link anyway? "
+			  "File %s already exists; make it a link anyway?"
 			  localname)))))
 	  (tramp-error v 'file-already-exists newname)
 	(delete-file newname)))
@@ -3463,7 +3463,7 @@ User is always nil."
     (or ;; Maybe there is a default value.
      (tramp-get-method-parameter v 'tramp-case-insensitive)
 
-     ;; There isn't. So we must check, in case there's a connection already.
+     ;; There isn't.  So we must check, in case there's a connection already.
      (and (file-remote-p filename nil 'connected)
           (with-tramp-connection-property v "case-insensitive"
 	    (ignore-errors
@@ -3694,7 +3694,7 @@ User is always nil."
 			  (yes-or-no-p
 			   (concat
 			    "Backup file on local temporary directory, "
-			    "do you want to continue? ")))))
+			    "do you want to continue?")))))
 	  (tramp-error v 'file-error "Unsafe backup file name"))))))
 
 (defun tramp-handle-insert-directory
@@ -3915,7 +3915,7 @@ Return nil when there is no lockfile."
 			    (yes-or-no-p
 			     (concat
 			      "Lock file on local temporary directory, "
-			      "do you want to continue? ")))))
+			      "do you want to continue?")))))
 	    (tramp-error v 'file-error "Unsafe lock file name")))
 
 	;; Do the lock.
@@ -4274,13 +4274,13 @@ support symbolic links."
        ((eq async-shell-command-buffer 'confirm-kill-process)
 	;; If will kill a process, query first.
 	(if (yes-or-no-p
-	     "A command is running in the default buffer.  Kill it? ")
+	     "A command is running in the default buffer.  Kill it?")
 	    (kill-process p)
 	  (tramp-user-error p "Shell command in progress")))
        ((eq async-shell-command-buffer 'confirm-new-buffer)
 	;; If will create a new buffer, query first.
 	(if (yes-or-no-p
-	     "A command is running in the default buffer.  Use a new buffer? ")
+	     "A command is running in the default buffer.  Use a new buffer?")
             (setq output-buffer (generate-new-buffer bname))
 	  (tramp-user-error p "Shell command in progress")))
        ((eq async-shell-command-buffer 'new-buffer)
@@ -4289,7 +4289,7 @@ support symbolic links."
        ((eq async-shell-command-buffer 'confirm-rename-buffer)
 	;; If will rename the buffer, query first.
 	(if (yes-or-no-p
-	     "A command is running in the default buffer.  Rename it? ")
+	     "A command is running in the default buffer.  Rename it?")
 	    (progn
 	      (with-current-buffer output-buffer
 		(rename-uniquely))
@@ -4492,7 +4492,7 @@ of."
 	       (or (eq mustbenew 'excl)
 		   (not
 		    (y-or-n-p
-		     (format "File %s exists; overwrite anyway? " filename)))))
+		     (format "File %s exists; overwrite anyway?" filename)))))
       (tramp-error v 'file-already-exists filename))
 
     (let ((file-locked (eq (file-locked-p lockname) t))
@@ -5468,7 +5468,7 @@ this file, if that variable is non-nil."
 			  (yes-or-no-p
 			   (concat
 			    "Autosave file on local temporary directory, "
-			    "do you want to continue? ")))))
+			    "do you want to continue?")))))
 	  (tramp-error v 'file-error "Unsafe autosave file name"))))))
 
 (defun tramp-subst-strs-in-string (alist string)

lisp/net/trampver.el

@@ -29,7 +29,7 @@
 
 ;;; Commentary:
 
-;; Convenience functions around the Tramp version. Partly generated
+;; Convenience functions around the Tramp version.  Partly generated
 ;; during Tramp configuration.
 
 ;;; Code:

test/lisp/net/tramp-tests.el

@@ -2083,7 +2083,7 @@ Also see `ignore'."
       "/method:host:/:/path//foo"))
 
     ;; Forwhatever reasons, the following tests let Emacs crash for
-    ;; Emacs 25, occasionally. No idea what's up.
+    ;; Emacs 25, occasionally.  No idea what's up.
     (when (tramp--test-emacs26-p)
       (should
        (string-equal
@@ -4464,7 +4464,7 @@ This tests also `make-symbolic-link', `file-truename' and `add-name-to-file'."
 	      (should (string-equal (format "%s\n" fnnd) (buffer-string)))
 	      (should-not (get-buffer-window (current-buffer) t))
 
-	      ;; Second run. The output must be appended.
+	      ;; Second run.  The output must be appended.
 	      (goto-char (point-max))
 	      (should (zerop (process-file "ls" nil t t fnnd)))
 	      ;; `ls' could produce colorized output.
@@ -4588,8 +4588,10 @@ This tests also `make-symbolic-link', `file-truename' and `add-name-to-file'."
 		(should
 		 (string-match-p
 		  (if (memq process-connection-type '(nil pipe))
-		      "66\n6F\n6F\n0D\n0A\n"
+		      ;; `telnet' converts \r to <CR><NUL> if `crlf'
-		    "66\n6F\n6F\n0A\n0A\n")
+		      ;; flag is FALSE.  See telnet(1) man page.
+		      "66\n6F\n6F\n0D\\(\n00\\)?\n0A\n"
+		    "66\n6F\n6F\n0A\\(\n00\\)?\n0A\n")
 		  (buffer-string))))
 
 	    ;; Cleanup.
@@ -4754,8 +4756,9 @@ If UNSTABLE is non-nil, the test is tagged as `:unstable'."
 	;; Cleanup.
 	(ignore-errors (delete-process proc)))
 
-      ;; Process with stderr buffer.
+      ;; Process with stderr buffer.  `telnet' does not cooperate with
-      (unless (tramp-direct-async-process-p)
+      ;; three processes.
+      (unless (or (tramp--test-telnet-p) (tramp-direct-async-process-p))
 	(let ((stderr (generate-new-buffer "*stderr*")))
 	  (unwind-protect
 	      (with-temp-buffer
@@ -4851,8 +4854,10 @@ If UNSTABLE is non-nil, the test is tagged as `:unstable'."
 		   (string-match-p
 		    (if (memq (or connection-type process-connection-type)
 			      '(nil pipe))
-			"66\n6F\n6F\n0D\n0A\n"
+			;; `telnet' converts \r to <CR><NUL> if `crlf'
-		      "66\n6F\n6F\n0A\n0A\n")
+			;; flag is FALSE.  See telnet(1) man page.
+			"66\n6F\n6F\n0D\\(\n00\\)?\n0A\n"
+		      "66\n6F\n6F\n0A\\(\n00\\)?\n0A\n")
 		    (buffer-string))))
 
 	      ;; Cleanup.
@@ -5498,9 +5503,9 @@ Use direct async.")
           ;; Ignore trailing newline.
 	  (setq path (substring (shell-command-to-string "echo $PATH") nil -1))
 	  ;; The shell doesn't handle such long strings.
-	  (unless (<= (length path)
+	  (when (<= (length path)
-		      (tramp-get-connection-property
+		    (tramp-get-connection-property
-		       tramp-test-vec "pipe-buf" 4096))
+		     tramp-test-vec "pipe-buf" 4096))
 	    ;; The last element of `exec-path' is `exec-directory'.
             (should
 	     (string-equal
@@ -6154,6 +6159,12 @@ This requires restrictions of file name syntax."
   "Check, whether the sudoedit method is used."
   (tramp-sudoedit-file-name-p tramp-test-temporary-file-directory))
 
+(defun tramp--test-telnet-p ()
+  "Check, whether the telnet method is used.
+This does not support special file names."
+  (string-equal
+   "telnet" (file-remote-p tramp-test-temporary-file-directory 'method)))
+
 (defun tramp--test-windows-nt-p ()
   "Check, whether the locale host runs MS Windows."
   (eq system-type 'windows-nt))
@@ -6712,6 +6723,7 @@ process sentinels.  They shall not disturb each other."
 		   (tramp--test-sh-p)))
   (skip-unless (not (tramp--test-crypt-p)))
   (skip-unless (not (tramp--test-docker-p)))
+  (skip-unless (not (tramp--test-telnet-p)))
   (skip-unless (not (tramp--test-windows-nt-p)))
 
   (with-timeout