Re: [PATCH] Improved SSH host support for pcomplete/eshell

[Phil Hagelberg <phil@hagelb.org>]

On Wed, Dec 29, 2010 at 7:26 PM, Chong Yidong <cyd@stupidchicken.com> wrote:
> Phil Hagelberg <phil@hagelb.org> writes:
>> I've added support to pcmpl-ssh-hosts for it to parse ~/.ssh/config
>> as well instead of just ~/.ssh/known_hosts.
>
> Thanks.  If I understand correctly, this is only used to get ssh host
> aliases, right?  You should probably make a note of this improvement in
> NEWS.

That's correct. Here's an updated version of the patch that adds an entry to
NEWS and clarifies some of the docstrings.

-Phil

diff --git a/etc/NEWS b/etc/NEWS
index f21028a..b84ae9d 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -344,6 +344,9 @@ utf-8, and do the normal `undecided' decoding for the rest.

 ** Eshell changes

+*** Tab completion for SSH hosts now additionally uses hostname
+aliases from ~/.ssh/config rather than just known_hosts key entries.
+
 *** The default value of eshell-directory-name is a directory named
 "eshell" in `user-emacs-directory'.  If the old "~/.eshell/" directory
 exists, that is used instead.
diff --git a/lisp/pcmpl-unix.el b/lisp/pcmpl-unix.el
index f2c19ca..ff3d8e7 100644
--- a/lisp/pcmpl-unix.el
+++ b/lisp/pcmpl-unix.el
@@ -40,14 +40,21 @@

 (defcustom pcmpl-ssh-known-hosts-file "~/.ssh/known_hosts"
   "If non-nil, a string naming your SSH \"known_hosts\" file.
-This allows completion of SSH host names.  Note that newer
-versions of ssh hash the hosts by default to prevent
-Island-hopping SSH attacks.  This can be disabled, at some risk,
-with the SSH option \"HashKnownHosts no\"."
+This allows completion of SSH host names based on saved host
+keys.  Note that newer versions of ssh hash the hosts by default
+to prevent Island-hopping SSH attacks.  This can be disabled, at
+some risk, with the SSH option \"HashKnownHosts no\"."
   :type '(choice file (const nil))
   :group 'pcmpl-unix
   :version "23.1")

+(defcustom pcmpl-ssh-config-file "~/.ssh/config"
+  "If non-nil, a string naming your SSH \"config\" file.
+This allows completion of SSH host names based on configured aliases."
+  :type '(choice file (const nil))
+  :group 'pcmpl-unix
+  :version "24.1")
+
 ;; Functions:

 ;;;###autoload
@@ -138,7 +145,7 @@ documentation), this function returns nil."
 ;; ssh support by Phil Hagelberg.
 ;; http://www.emacswiki.org/cgi-bin/wiki/pcmpl-ssh.el

-(defun pcmpl-ssh-hosts ()
+(defun pcmpl-ssh-known-hosts ()
   "Return a list of hosts found in `pcmpl-ssh-known-hosts-file'."
   (when (and pcmpl-ssh-known-hosts-file
              (file-readable-p pcmpl-ssh-known-hosts-file))
@@ -153,6 +160,27 @@ documentation), this function returns nil."
             (add-to-list 'ssh-hosts-list (match-string 1))))
         ssh-hosts-list))))

+(defun pcmpl-ssh-config-hosts ()
+  "Return a list of host aliases found in `pcmpl-ssh-config-file'."
+  (when (and pcmpl-ssh-config-file
+             (file-readable-p pcmpl-ssh-config-file))
+    (with-temp-buffer
+      (insert-file-contents-literally pcmpl-ssh-config-file)
+      (let (ssh-hosts-list
+            (case-fold-search t))
+        (while (re-search-forward "^ *host\\(name\\)? +\\([-.[:alnum:]]+\\)"
+                                  nil t)
+          (add-to-list 'ssh-hosts-list (match-string 2)))
+        ssh-hosts-list))))
+
+(defun pcmpl-ssh-hosts ()
+  "Return a list of known SSH hosts.
+Uses both `pcmpl-ssh-config-file' and `pcmpl-ssh-known-hosts-file'."
+  (let ((hosts (pcmpl-ssh-known-hosts)))
+    (dolist (h (pcmpl-ssh-config-hosts))
+      (add-to-list 'hosts h))
+    hosts))
+
 ;;;###autoload
 (defun pcomplete/ssh ()
   "Completion rules for the `ssh' command."