Evaluate a variable when inserting text into a buffer

Question

When I open a fresh file for coding, I like to insert a header like this:

#####################################################################   
# Purpose:
# Author: me (me@someplace.com)
# Date:
#####################################################################

I keep this text in a file called header in ~/.emacs.d/ and I insert it like so:

;; Insert header to file 
(defun header()
  "Insert header into file"
  (interactive)
  (insert-file "~/.emacs.d/header"))

which I call with M+x header. Very cool! I also have a function for adding the date:

;; Insert today's date
(defun today ()
  "Insert today's date"
  (interactive)
  (insert (format-time-string "%Y-%m-%d")))

which I invoke with M+x today after inserting my header text in order to populate the Date: field.

Q: Is there a way that I can merge these functions such that the date is automatically inserted after Date: when I insert my header text? For example, can I add (format-time-string "%Y-%m-%d") after Date: in my header file and evaluate it somehow when it is inserted?

You need something along the following lines: ```(defun header() "Insert header into file" (interactive) (progn (insert-file "~/.emacs.d/header") (re-search-backward "Date: ") (insert (format-time-string "%Y-%m-%d"))))``` — aadcg, Oct 29 '20 at 15:47
Whoa – that's magical! Care to turn it into an answer so I can mark this answered? (I found that I had to change `re-search-backward` to `re-search-forward` since the text is inserted after the cursor, presumably?) — Dan, Oct 29 '20 at 15:53
There are lots of generic mechanisms for inserting templates in emacs. See e.g. [skeleton](https://www.gnu.org/software/emacs/manual/html_mono/autotype.html#Skeleton-Language) in the Autotyping manual. See also [Category Templates](https://www.emacswiki.org/emacs/CategoryTemplates) in the Emacs Wiki. — NickD, Oct 29 '20 at 15:59

score 2 · Accepted Answer · edited Nov 06 '20 at 15:04

2

Inside of GNU Emacs only your imagination is the limit :)

I think you're looking for something along the following lines, though some adjustments might be needed.

(defun header()
  "Insert header into file"
  (interactive)
  (insert-file "~/.emacs.d/header")
  (re-search-backward "Date:")
  (insert (format-time-string "%Y-%m-%d")))

edited Nov 06 '20 at 15:04

Phil Hudson

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answered Oct 29 '20 at 15:58

aadcg

1,203
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Evaluate a variable when inserting text into a buffer

1 Answers1