Automated updates: 2023-12-27

2023-12-27-too-late.md

@@ -0,0 +1,56 @@
+---
+layout: post
+title: Scheduling Reminders, but Not Too Late
+date: 2023-12-27 07:22:05-0500
+categories:
+tags: [linux, programming, techtips]
+summary: Checking if an arbitrary time of day passed or comes later
+thumbnail: /blog/assets/2054250017_3e12f12ae9_o.png
+offset: -34%
+teaser: I had too many days when reminders to publish posts came on the wrong day; this fixes that with some Linux magic.
+spell: ntfy atq atrm ampm aplay usr fi Stenning
+proofed: true
+---
+
+This should go quickly, but at least I can actually put some code on the blog for the first time in months...
+
+![An analog alarm clock on an end table](/blog/assets/2054250017_3e12f12ae9_o.png "Wake up!")
+
+I've mentioned before that I have a script that I run overnight.  I don't publish the whole thing, because I have most of it tuned for my extremely specific use cases, but have extracted and published the most reusable bits of it as part of my [**Periodic Scripts**](https://github.com/jcolag/periodic-scripts) repository.
+
+For the blog, I find it especially important for that script to set a hacked-together alarm to remind me to rebuild and publish the blog when the next post goes out.  Most reminders use a system sound to get my attention if I step away from the computer, [`ntfy`](https://github.com/dschep/ntfy) to show a desktop notification, and [`at`](https://opensource.com/article/21/8/linux-at-command) to set the time.
+
+However, this scheme has a fatal-adjacent flaw.
+
+If I set the publication time on the post too early, sleep in some morning, or otherwise end up in a situation where the system tries to set the alarm *after* I claimed that I wanted to get the post out, `at` always picks the next occurrence of the specified time.  Therefore, waking up late sets the alarm for the following day.
+
+Normally, I can catch that manually.  When I notice that I've run late, I use `atq` and `atrm` to drop the incorrect reminders.  If I don't notice, though, then an alarm goes off the next morning and I have to remember why.  But I shouldn't need to do that.
+
+When the issue came up, recently, and I also had some free time to look into it, I realized that I could compare the desired time with the time that the script runs, and make the decision then.  I needed two key pieces of information.  First, as I already knew, and you've probably seen come up on the blog before, the `date` command can take a `+%s` format to provide seconds since 1970.  More surprising, though, if you only give `date` a time of day, it assumes that you want to parse the time as if it happens *today*.  Combining the two, we get two timestamps, assuming that `$time` holds a string with the intended time of day, such as "`6:28 AM`," "`2:58 PM`," or "`17:38`."
+
+```sh
+publish=$(date -d "${time}" "+%s")
+now=$(date "+%s")
+```
+
+Once we have that information, I can compare the times and decide whether to set an alarm for later or trigger a notification now.
+
+```sh
+if [ $publish -gt $now ]
+then
+  ampm=$(date -d "${time}" "+%I:%M %p")
+  ntfy send "${filename}" | at "${ampm}"
+  echo "aplay /usr/share/sounds/sound-icons/prompt.wav" | at "${ampm}"
+else
+  ntfy send "Today's post (${title}) needs rescheduling..."
+  echo aplay /usr/share/sounds/sound-icons/cembalo-2.wav
+fi
+```
+
+I believe that the "sound icons" come installed by default with Debian-derived Linux distributions.  Most of the sounds seem distinct enough and so rarely used that you can quickly recognize their new usage.
+
+I told you that this would go quickly...
+
+* * *
+
+**Credits**:  The header image is adapted from [First photo](https://www.flickr.com/photos/nickstenning/2054250017) by [Nick Stenning](https://www.flickr.com/photos/nickstenning/), made available under the terms of the [Creative Commons Attribution Share-Alike 2.0 Generic](https://creativecommons.org/licenses/by-sa/2.0/) license.