Tag Archives: cron

Public Code Number One

Today I finally released my first public code into the wild. I’ve been teaching myself programming, and throughout the learning process, my code has been in private repositories with Bitbucket. It was a struggle to feel confident enough to put anything of my own on Github, but I realized I have nothing to be afraid of. As a newcomer to the programming world, I’ve had what many refer to as impostor syndrome. Even though I’ve read style guidelines and paid close attention to how others publish code, there’s been an underlying fear of criticism without any constructive suggestions. What I realized is how silly that sounds. In my time browsing Github, I don’t recall thinking anyone was a total jerk. There have been disagreements, sure, but no trolling and certainly nothing like a lot of other places on the internet. I know my script works, so I added a license, a nice README.md, and pushed it out into the world!

The repo I pushed is a little script that checks whether or not a website can be reached. It then logs the result to a text file and, if provided with an email, sends an alert when the site is down. I have it set up to run as a cronjob on my home server. Every ten minutes it checks my site and that of my wonderful partner in everything, Kenzie. Her web host unfortunately put her site on a server that was having a lot of downtime problems. In order to get an idea of how bad the problem was, I thought it would be perfect to have a log we could refer to. The notification email wasn’t 100% necessary, but it seemed like a neat idea and I really wanted to learn how to send emails from my machine! I was right, it turned out to be a fun feature and I had a great time setting up my first Postfix server.

Overall I feel really good about this first step. It may just be a simple script, but it represents much more than that to me. A metaphorical door in my mind has been opened to feeling comfortable doing this again. There’s another project I’ve been working on that’s getting close to ready. This one, however, is a command-line app. That means it will also be released as a Gem, Ruby’s software packaging system. The code won’t just be hosted on Github, but also on rubygems.org. It would be usable by anyone with Ruby installed, simply using ‘gem install’. Makes me a bit more nervous about it, but I really like how the program is coming out and I’m actually getting pretty excited to share it!

I Forgot My Newline

This is a friendly reminder to always leave a blank line at the end of your text files. You might be thinking that it doesn’t really matter, and in many cases you’d probably be correct. However, there are also plenty of configuration files for apps that require it to be there. Those that do will most likely not tell you so it would be quite hard to find and fix the problem.

Technically, a text file is just a series of lines ending in a newline character “\n”. On very old systems, a file without the ending newline would not even be considered a text file. Operating systems and applications nowadays can handle this and still read the file, but not without problems. The most likely issue is that the last line will be completely ignored. Due to the missing newline, it’s not even considered a line of text. Hope the last line of your file wasn’t important!

A prime example is cron in Unix-like operating systems. Filling up the last line in a crontab and forgetting to add a newline at the end is one of the most common problems people run into when new to cron. That last command at the end of the crontab will simply not run.

I’ve run into this a few times in the past, so I decided to look it up and find out the deeper reasons behind programs expecting “\n”. I thought it would be interesting, and it was. I hope you’ve learned a useful tip, even if you don’t care about the reasons behind it.

If you want to be sure to never have this problem, check out Sublime Text, my favorite text editor for code and everything else. It has an option to force a newline at the end of a file on saving. Sweet! If you are already using Sublime Text, see my previous post on replacing the default icon with something much cooler.