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authorSteph Enders <steph@senders.io>2024-03-07 15:17:29 -0500
committerSteph Enders <steph@senders.io>2024-03-07 15:17:29 -0500
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+
+--post-date: 2019-02-17
+--type: blog
+ <article>
+ <h1>Venturing back into C</h1>
+ <p>For the past two weeks or so I have been diving back into C
+ programming. I&#39;ve found it to be a very fun and refreshing experience
+ coming off of a slog of Java 11 updates at work. I&#39;ve found comfort
+ in its simplicity and frustrations in my &quot;I can do this without an
+ IDE&quot; mindset.</p>
+ <p>I started C programming in College during a 8 AM course of which all I
+ can remember is that it was at 8 AM. I loved programming in C, dealing
+ with memory, pointers, no strings, structs, no strings, linking, no
+ strings. It was a really interesting difference from the web and Java
+ programming I had done previously. Obviously the lack of the
+ &quot;string&quot; type made things interesting and initially a challenge
+ for me back then. In my most recent endevour I found <code class=
+ 'inline'>char *</code> to be perfectly suitable for every case I came
+ across. It was usually a separate library that was failing me, not a
+ fixed char array. This was mostly due to the types of programs I was
+ writting in college were text adventures where all of what I did was
+ using strings. And my lack of understanding of what was actually
+ happening in C was really what was causing all the issues.</p>
+ <h2>The Project</h2>
+ <p>I started working on an application I had been meaning to develop
+ called <a href=
+ 'https://github.com/s3nd3r5/reminder'><b>reminder.d</b></a>. This daemon
+ would monitor for reminder notifications I would send via a CLI. It queue
+ them up based on some time set to send the notification. I ended up
+ writing both the CLI and the daemon in this past week, both in C.</p>
+ <h3>The Beginning</h3>
+ <p>This project started with an outline (as a README) which I think was
+ the reason this ended up as an actually successful project. I had been
+ thinking about this for a long time, and had begun using a calendar to
+ keep track of long term reminders/dates etc. First, I outlined the
+ architecture &quot;how would I actually do want to send myself
+ remidners&quot;. Since half my day is spent infront of a computer, with a
+ terminal open or at least two keystrokes away, a CLI would do the trick.
+ Then how do I actually send myself notifications... writing them down. So
+ I can use the CLI to write to a file and have a daemon pick up the
+ changes and notify me once it hits the desired time posted.</p>
+ <h3>The CLI</h3>
+ <p>The CLI <b>remindme</b> took in messages and appened them to a file.
+ This file would be monitored by the daemon later on. Each reminder
+ consisted of three parts:</p>
+ <ul>
+ <li><i>Message</i> - The body of the notification.</li>
+ <li><i>Time</i> - This is either a datetime or a period for when the
+ notification should send.</li>
+ <li><i>Flag</i> - The Flag was set by the CLI when written to the file,
+ this marks the status of the reminder</li>
+ </ul>After a notification is written the daemon will pick up the
+ notification and notify if the time set is now/past.
+ <h3>The Daemon</h3>
+ <p>The Daemon <b>reminder-daemon</b> opened and tailed a file at
+ <i>/usr/local/etc/reminder.d/$USER.list</i>. It would tail the file
+ monitoring any incoming lines parsing them into reminders. The syntax of
+ the reminder is <code class='inline'>FLAG EPOCHSEC MESSAGE</code> .
+ Tokenizing on spaces it was then added to a linked-list sorted by time.
+ Every second it checks the file for any new lines, adding reminders as
+ they come in, then check the head of the list. If the reminder at the
+ head is ready to be notified the daemon pops it off the list and sends
+ the notification. After a notification is sent successfully the daemon
+ modifies that line in file updating its <code class='inline'>FLAG</code>
+ to &#39;d&#39;. This is so when the daemon starts back up it skips the
+ reminder. Notifications are sent via <i>libnotify</i>: <code class=
+ 'inline'>Reminder - $DATETIME</code> with the message body. They are also
+ set to last until dismissed manually, this way if were to walk away, once
+ I sat down I&#39;d see the stale reminder waiting.</p>
+ <h3>Future Plans for Reminder.d</h3>
+ <p>Having a system to create and send myself notifications is incredibly
+ useful but having them limit to just the computer I sent them on makes
+ them a very limited. I have been using them at work for the last few days
+ and its nice to be able to tell myself to remeber to email a person after
+ lunch. But I would like to be able to tell myself things later in the
+ day. I have planned since the beginning to have a remote server I can
+ sync the reminders through. In addition having an application running on
+ my phone that also gets and sets reminders.</p>
+ <p>Remote syncing would change entirely how I deal with reminders in the
+ file.</p>
+ <pre>
+<code>
+ struct remnode {
+ long fileptr;
+ struct reminder* reminder;
+ struct remnode* next;
+ };
+ </code></pre>
+ <p>Is currently the struct I use to keep track of the reminders.
+ <code class='inline'>fileptr</code> is the line of the file where the
+ reminder is, so I can <code class='inline'>fseek</code> back to the
+ location and overwrite its flag. I cannot currently think of a way to
+ keep the files perfectly identical without introducing countless
+ edgecases. What I do think might work is providing some form of UUID.
+ When a remote pull tells the systems daemon that a notification has been
+ cleared it can mark it by ID. Right now the fileptr is effectively its
+ ID, but that will not work anymore. A composite key of the daemons own id
+ (generated at install?) with a new ID of each incoming message would help
+ ensure uniqueness across ID generations across multiple systems.</p>
+ <h2>What I&#39;ve learned</h2>
+ <p>First off, I probably could&#39;ve done this in bash. With
+ <code class='inline'>date notify-send git awk cron</code> and a few other
+ useful commands I could very easily keep track of file changes and push
+ notifications at a certain time. But seeing as I scrap together bash
+ scripts all the time I though C would make things more fun.</p>
+ <p>Writing manpages was the probably the most fun I had working on the
+ project. They have a simple elegance to them, similar to C. That being
+ said you could FEEL the age of the language. Every single decision is
+ there to make things simple to parse. Even compared to modern markup the
+ explicit direct nature of the language made it so easy to learn. Every
+ tag served a specific purpose and each objective I had had a flag to do
+ it.</p>
+ <pre><code>
+.TH REMINDME 1
+.SH NAME
+ remindme \- Send yourself reminders at a specific time on one or more devices
+.SH SYNOPSIS
+.B remindme
+[\fB\-t\fR \fITIME\fR]
+[\fB\-\-at \fITIME\fR]
+[\fB\-i\fR \fIPERIOD\fR]
+[\fB\-\-in\fR \fIPERIOD\fR]
+ </code>
+ </pre>
+ <p>Libnotify was insanely easy to work with, from a programming
+ perspective.</p>
+ <pre><code>
+ NotifyNotification *notif = notify_notification_new(title, rem-&gt;message, &quot;info&quot;);
+ notify_notification_set_app_name(notif, APP_NAME);
+ notify_notification_set_timeout(notif, NOTIFY_EXPIRES_NEVER);
+
+ GError* error = NULL;
+ gboolean shown = notify_notification_show(notif, &amp;error);
+ </code>
+ </pre>
+ <h2>In closing</h2>
+ <p>Overall, this was an extremely fun first week of engineering. I look
+ forward to what I am able to do syncing and sending notifications on
+ android.</p>
+ <p>For the zero people reading, grab a beer and outline your project.
+ Full through. Think about the how, then write it down. Don&#39;t worry
+ about getting in the weeds of how to write a manfile, thats what is fun
+ about programming. I thought I botched my debian/sid environment
+ uninstalling and reinstalling a notification daemon. Infact I think its
+ caused me to take a stance on the whole systemd thing. Either way, start
+ a private repo (they&#39;re free now) write a README and a LICENSE file
+ and iterate on the README until you realize &quot;oh shit this is
+ something I can do&quot;. Then do it. This project still needs some work,
+ but for an MVP, its actually done. And now I can dive in the deep end of
+ trying to actually make it easy to setup on a fresh PC. Or dive into
+ modern android development and server syncing...</p>
+ </article>
+