Dates Are Easy

It’s hard to believe it, but computers can do what users tell them, instead of the other way around.

– Tim Marinin

Got an enlightenment yesterday¹ night.

Up until yesterday, I put the date into the files for this website by hand. That’s actually not hard, but not comfortable either, and the more I did it, the less comfortable it felt. Like a pebble in a shoe.

The source for pages in Hugo is Markdown files that have meta-information added in the form of a TOML (or YAML, or even JSON, whatever you like) header called “Front Matter” in Hugo terms. For instance, here’s how the file with this very post begins:

+++
title = "Dates Are Easy"
subtitle = "automatization — not so much"
date = 2020-10-16T12:55:25+03:00
tags = ["linux", "hugo", "school didn't teach me this"]
categories = ["IT"]
+++
> It's hard to believe it, but computers can[...]

As you can see, the date is an ISO 8601 string. Composing that string by hand every time is not that much fun. I need to have the current date (because the current date is what I’m usually looking for here) inserted automatically. But how?

Simply taking a Git commit date (since it’s all stored in Git anyway) is not a good solution: the date would change every time I fix some typos of formatting.²

Hugo has a builtin solution in the form of file templates. It can be arranged so that a command like

$ hugo new /posts/2020/date.md

creates a file with the current date already pre-populated in the Front Matter (as well as some other fields, if required). This suits fine for short notes, but a post, even if it isn’t too long, can take quite some time to write,³ and I want it to have the date (and time) of when it was finished, not of when the first idea appeared and the file got created.

I even started contemplating using a Vim plugin that can paste the date in the required format, between other things. Unfortunately, I don’t feel comfortable composing posts in Vim⁴, and ReText that I am currently writing this post in has no plugins.

It finally dawned on me yesterday:

What exactly prevents me from inserting the current date by means of the system?!

Isn’t it Linux that I’m using? I’ve been told that in Linux one can do anything — and even more. Can I not make it paste the current date in ISO 8601 format wherever I please? I can, actually!

Any decent system interface allows binding an arbitrary command to a keyboard shortcut, and so does KDE that I use. Let’s say it’s Ctrl-Alt-D. I only need to figure out the command to paste the current date. And to paste where, by the way?

I failed to promptly find a command to paste some arbitrary text to the cursor position in any window. Instead, I found the xsel utility that works with the system clipboard and can put the current date there. Let’s give it a try:

date -Is | tr -d "\n" | xsel -b -i

It works!⁵ The current date appears in the clipboard, formatted appropriately, and then a ‘Ctrl-V’ (or a ‘Shift-Ins’, whichever you like more) can be used to paste the date anywhere. But it takes two keyboard combinations, and the clipboard gets overwritten — somewhat messy. I’d like it to be one shortcut, and keeping the clipboard intact…

Google tells me there’s an xdotool that can do the typing for me. Can I make it work with a keyboard shortcut? Let’s try to bind something like

xdotool type "test"

to Ctrl-Shift-T and give it a try in a text editor… Oops! A “save as” dialog opened up. What the hell?!

It turns out, xdotool does type, but the keyboard input is still processed, and I have Ctrl and Shift pressed! So the text editor (it was Kate on the occasion) didn’t get a Ctrl-Shift-T (that one was caught by the system) but received Ctrl-Shift-E (that had no meaning), then Ctrl-Shift-S (“save as”), and then Ctrl-Shift-T again, which was ignored because the “save as” dialog was already opened.

That won’t do! Fortunately, xdotool has the --clearmodifiers option that “releases” all the keys (including CapsLock) before typing and re-presses them again after the job is done. Trying this…

Much better. xdotool also “released” the T, so the first letter did not appear, and afterwards “re-pressed” Ctrl and Shift (which made the text editor’s behavior very weird until I pressed this combination again), but that’s not a big deal: my shortcut uses D that never appears in the date string, and I can ask xdotool to “release” the keys it “re-pressed” again:

xdotool type --clearmodifiers $(date -Is | tr -d "\n") && xdotool keyup ctrl alt d

Pressing Ctrl-Alt-D…

There we go! It works everywhere, be it the console, or ReText, or even Vim…

Of course, figuring it all (especially xdotool) out took time⁶. Of course, someone may call it all “unnecessary geekery”. But my computer now does what I want it to do the way I want. Which is actually the reason to own a computer in the first place…

I think these things need to be taught at school.