Emacs: Key Macro Example: Modify Webfeed Entries

By Xah Lee. Date: . Last updated: .

Here's a example of Emacs: Keyboard Macro use.

I have a webfeed file blog.xml in Atom Webfeed format. There are many text blocks like this:

<entry>
  <title>…</title>
  <id>…</id>
  <updated>…</updated>
  <summary>…</summary>
  <content type="xhtml">
<div xmlns="http://www.w3.org/1999/xhtml">
<p>see <a href="http://xahlee.blogspot.com/2011/11/emacs-lisp-exercise-insert-random-uuid.html">http://xahlee.blogspot.com/2011/11/emacs-lisp-exercise-insert-random-uuid.html</a></p>
</div>
  </content>
 <link rel="alternate" href="http://xahlee.org/emacs/blog.html"/>
</entry>

I need to remove the “content” part and simply put the URL in the alternate link, like this:

<entry>
  <title>…</title>
  <id>…</id>
  <updated>…</updated>
  <summary>…</summary>
 <link rel="alternate" href="http://xahlee.blogspot.com/2011/11/emacs-lisp-exercise-insert-random-uuid.html"/>
</entry>

Kmacro is excellent solution for this. You just call interactive search to move cursor to places you want, and do delete or copy and paste. Like this.

  1. isearch-forward 【Ctrl+s】 for http://xahlee.blogspot.
  2. isearch-backward 【Ctrl+r】 for ", move cursor forward 1 position, set mark.
  3. isearch-forward for ", do a copy. Now the blog URL is in clipboard
  4. isearch-backward for <content , set mark.
  5. isearch-forward for </content>.
  6. Press delete to delete the content section.
  7. isearch-forward for href=.
  8. Do steps to delete the URL (using isearch and set mark like above), then paste the new one.

Once i recorded these steps, then i call kmacro-end-and-call-macro 【Ctrl+x e】. This way, every 2 keystrokes makes one entry change. This allows me to visually verify what i've done is correct. I could also press Ctrl+u, then a number, then Ctrl+x e to repeat it automatically n times.

Emacs Keyboard Macro