Tyler Oderkirk's Blog » Emacs

Setting file modes with Dired

Tyler — Fri, 14 Dec 2007 17:33:59 +0000

I’ve been writing a lot of shell scripts recently in emacs. I used to go to a shell to `chmod u+x` the new scripts, but now I do it within Emacs:

Do `M-x dired` from the buffer editing a new script. I’ll give you a Dired buffer rooted in that script’s directory.
`C-s` to find the script’s entry and then press `M` to change its mode.
Dired speaks symbolic modes, so I just use `u+x` (give user the execute permission)

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The sound of a 5linx videophone demo downstairs. They sell for $200 and the monthly service is ~$30/mo. Dave is selling them, so let me know if you’re interested or would like to see one in action.

Editing files as root with Emacs and Tramp

Tyler — Mon, 10 Sep 2007 00:50:42 +0000

Did you know that you can use an existing non-privileged instance of Emacs to open files as root? Yep, Emacs includes a module called TRAMP which can use sudo to read and write files.

As is usually the case, I had to work sweat a little to make it work. My problem was that my zsh prompt was too fancy. The solution was to toss this conditional in at the end of my .zshrc:


if [ $TERM = "dumb" ]; then
   unsetopt zle
   export PS1="%% "
fi

This works by disabling the zsh line editor (“zle”) and setting a plain vanilla prompt (“PS1″) that tramp can recognize when it logs in.

TRAMP is a little slow on my machine but it sure beats firing up a new Emacs instance every time I want to edit `/etc/superdooper.conf`

Turn on the bright lights – Emacs highlighting

Tyler — Wed, 02 May 2007 19:24:54 +0000

Want to highlight every line in the current Emacs buffer that matches a regexp? Try `highlight-regex`. It serves a purpose similar to `M-x occur` (or better yet, icicle-occur). The highlighting regexs are re-evaluated every time the buffer changes ie the effect is sticky. Use `M-x unhighlight-regex` to disable these.

Want to see what you’ve changed since a buffer’s file was opened? Use `highlight-changes-mode`. It supports “next/prev change” movement and coloring based on change “age”. `highlight-compare-with-file` sounds like a nice alternative to `ediff-buffer-with-file` and `ediff-backup`.

Bonus: light-symbol-mode – Higlight all occurances of whatever symbol the cursor is on

emacs-snapshot-gtk emacsclient and using ediff for regions

Tyler — Sun, 11 Feb 2007 20:09:23 +0000

If you’re using the emacs-snapshot-gtk package (I use the one from Alexandre’s repository) and you want to use emacsclient, make sure you use the version that it supplies at `/usr/bin/emacsclient.emacs-snapshot`. If you just run emacsclient, it might confusingly say “emacsclient: can’t stat /tmp/esrv1000-yourhost: Success”

Recently at work I’ve been using ediff to compare little pieces of output from one of our devices. Here’s how I go about it:

Paste the first blob of text (“B1″) into a scratch buffer.
Hit Enter a few times to separate the blobs. Paste the second blob (“B2″).
Run (e.g. with M-x) ediff-regions-wordwise (or -linewise if you prefer)
Tell ediff that Region A and Region B are in the same scratch buffer.
Mark B1 as Region A and with `C-SPC` and `C-M-c`.
Mark B2 as Region B in the same way.

If you find yourself in some distopian parallel universe where emacs doesn’t exist, you might be able to get away with the following shell one-liner. Your shell will need support command substitution with the `<(foo)` syntax, like bash and zsh do.

$ diff -u <(echo "asdf") <(echo "zxcv")

Multiline gets a little hairy…

% diff -u <(echo "one
cmdsubst> two
cmdsubst> three") <(echo "one
cmdsubst> honk
cmdsubst> three")
--- /proc/self/fd/11 2007-02-11 12:38:28.680341500 -0500
+++ /proc/self/fd/16 2007-02-11 12:38:28.680341500 -0500

@@ -1,3 +1,3 @@
one
-two
+honk