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+;;;;;
+title: C-d to close eshell
+tags: eshell, emacs, elisp, config
+date: 2013-08-17 02:25
+format: md
+;;;;;
+
+One of the "tricks" that I have learned to use when working with
+terminals is using `C-d` to close them, or when working on a TTY
+logout. It somehow grew to the extent that if I can't use it, I get
+annoyed, like with `eshell`.
+
+I have customized `ansi-term` to immediately close its buffer after the
+shell quits. This makes it very easy to start an `ansi-term`, which I've
+bound to `C-c t`, run a quick command (perhaps `make`, or similar), `C-d`,
+and I'm out. I want that for my `eshell` too.
+
+There are a few conditions that I want met before the buffer is
+killed, though.
+
+1. Since `eshell` is an Emacs mode like any other, `C-d` is usually used
+   to forward-kill characters, I don't want to lose this.
+2. I only want it to quit when the line of input is empty.
+
+The following piece of code make sure these conditions are met.
+
+1. It interactively calls `delete-char`, which keeps keybindings like
+   `C-4 C-d` to delete 4 characters working.
+2. It catches the error condition which is signaled whenever
+   `delete-char` can't do it's job (like when there's nothing left to
+   delete in the buffer).
+3. It checks to make sure that the signaled error is the `end-of-buffer`
+   error. I don't want to kill the buffer if I try to delete more
+   characters than are in the buffer because I feel that could cause
+   irritating surprises.
+4. It checks of the cursor is at the `eshell` prompt. This, combined
+   with only responding to the `end-of-buffer` error, makes sure we're
+   on an empty line and not just at the end of the input. Sometimes
+   keys are pressed at the wrong time and I don't want to have to
+   re-type a command just because I was being an idiot.
+5. If the right conditions aren't met, signal the error again so I can
+   see what's going on.
+
+``` emacs-lisp
+(defun eshell-C-d ()
+  "Either call `delete-char' interactively or quit."
+  (interactive)
+  (condition-case err
+      (call-interactively #'delete-char)
+    (error (if (and (eq (car err) 'end-of-buffer)
+                    (looking-back eshell-prompt-regexp))
+               (kill-buffer)
+             (signal (car err) (cdr err))))))
+```
+
+I then bind this to `C-d` in eshell.
+
+``` emacs-lisp
+(add-hook 'eshell-mode-hook
+          (lambda () (local-set-key (kbd "C-d") #'eshell-C-d)))
+```