Forem: Willem van den Ende

How to replace an org-mode link by its description

Willem van den Ende — Tue, 23 Feb 2021 10:24:02 +0000

Problem
Solution
Epilogue

Problem

Before turning a note into a blog post, I want to remove some of the org-mode links that are internal to my notes. There did not appear to be a way to do this out of the box. The answers I found on emacs stackexchange used regular expressions or deleted a space after the link.

I used a fair number of tabs to cobble up a solution, so I thought it would be worth sharing.

org-delete-link by a throw-away account almost worked, and uses org-modes’ Abstract Syntax Three through the org-element api. User Timm correctly pointed out a space after the link would also be deleted.

Solution

I prefer Andrew Swann’s name for the function, so here is my fixed mashup:

    (defun org-replace-link-by-link-description ()
      "Remove the link part of an org-mode link at point and keep
    only the description"
      (interactive)
      (let ((elem (org-element-context)))
        (if (eq (car elem) 'link)
            (let* ((content-begin (org-element-property :contents-begin elem))
                   (content-end  (org-element-property :contents-end elem))
                   (link-begin (org-element-property :begin elem))
                   (link-end (org-element-property :end elem)))
              (if (and content-begin content-end)
                  (let ((content (buffer-substring-no-properties content-begin content-end)))
                    (delete-region link-begin (- link-end 1))
                    (insert content)))))))

Subtract one from link-end and it works. This is the fixed line:

    (delete-region link-begin (- link-end 1))

Original question on emacs stackexchange: in org-mode, how to remove a link?

Epilogue

Why do I want this? I want to publish only some of my org-roam notes. Org-roam notes are like private wiki-pages. It also allows (with a bookmarklet) to clip webpages to their own org-roam note. At the top of the note, there is a roamkey that then contains the url of the page. I want to export my org-roam notes to markdown. Links should be to orignal webpages, instead of my private clippings with notes.

This is a baby step in the right direction.

FYI macs is perfectly usable without writing any code, using a distribution like Doom Emacs (my current) or Spacemacs (my previous). This is the first time in six years of regular emacs use that I’m writing a non-trivial amount of code for it.

How to 'fix' nodemon giving EADDRINUSE when changing a file

Willem van den Ende — Tue, 04 Aug 2020 10:08:21 +0000

TLDR: upgrade to nodemon 2.0.4 or higher.

Background

This was a '4 tabs problem' yesterday, posting this here to save you the trouble. I found quite a few solutions, including a recent one that were not as simple as just upgrading. What happened? I installed a starter kid for node.js, from someone else. It would serve my tiny experimental API just fine, but I'd get "Port already in use" after each server restart. Nodemon reloaded my server.js just fine, but it seemed the application port wasn't shut down soon enough.

Solution

Set "nodemon": "2.0.4" in package.json and you should be good to go.

Bonus - I learnt about 'fuser'

One of the incomplete solutions mentioned fuser, a handy linux command to work with open ports and files. fuser -k <YOURPORT>/tcp will kill the process using YOURPORT (adjust number to taste). It can do similar things for open files, as well as list them.

It does happen some times that I have development servers open, and can't use a port, but forgot which app is using that port, fuser is a quick way to find out which program it is, and if necessary kill it.

How to visualize a PostgreSQL schema as SVG with SchemaSpy

Willem van den Ende — Wed, 22 Jul 2020 16:15:05 +0000

TLDR: Use the option -imageformat svg to generate an ER diagram in SVG format
with SchemaSpy.

SchemaSpy generates HTML documentation from your database schema, including
Entity Relationship diagrams. I find visualization helpful as a database model
grows.

Out of the box it produces diagrams in png format, like this one in the Hasura
ecommerce example:

I prefer SVG, because it scales, is smaller, and it is all text.

Using SchemaSpy to see what the relations are like is not complicated, once you
have downloaded the dependencies and figured out the command line options. And
there are quite a lot of command line parameters. I had to download the
postgresql jdbc driver by hand, and specify the path with the -dp option:

<schemaspy-path>$ java -jar target/schemaspy-6.1.1-SNAPSHOT.jar \
  -t pgsql -host localhost -db postgres -o /tmp -u postgres -dp . -p postgres -imageformat svg

The -t option is mandatory. Probably works for anything that has a JDBC
Driver. I use a local database inside a docker container that is only open to my
machine, so I left the passwords and the port at the default settings the
docker-compose configuration came with.

See the comment by Jon Lauridsen below on how to do all of this with a docker one-liner.

If you forget an option, Schema Spy will tell you what was missing. I stuck the
above in a shell script inside my project, so I can easily generate it again. I
left the output as /tmp, so when I reboot (rarely), I am forced to create a
fresh diagram. Next step: integrate it into the build script, so I get
a fresh diagram whenever I add database migration files in the migrations directory.

SchemaSpy uses graphviz to generate images, the .dot files it uses as input, and
the generated images can be found in <outputpath>/summary/

At first I had a one liner for this, and then while writing the post, I found
that SchemaSpy supports SVG natively. It is 'just' another output parameter:

-imageformat svg

For more details, see the Get Started page in the SchemaSpy documentation .

I hope you found this helpful. It took me a bit of searching to find SchemaSpy, and the svg option. I'd be interested to know better alternatives, if there are any.

Forem: Willem van den Ende

How to replace an org-mode link by its description

Table of Contents

Problem

Solution

Epilogue

How to 'fix' nodemon giving EADDRINUSE when changing a file

Background

Solution

Bonus - I learnt about 'fuser'

How to visualize a PostgreSQL schema as SVG with SchemaSpy