Lying cat: Bizarre Filesystem Behaviour

Just a short post on something odd that happened to me last night.

I was working on the Jinja template to generate the posts on this website. I had a local server launched in the build directory of the website so I could preview the results as I went. It was working fine; I could make changes, rebuild, refresh, and immediately see those changes. The usual.

However, I noticed that the dates I wanted to appear underneath the title of blog posts were not showing up. I double checked the template, which seemed to be correct. It is a snippet like so:

{% if formatted_date is defined %}
<p id="date">{{formatted_date}}</p>
{% endif %}

The odd thing was that in the rendered templates I was viewing in the browser, the actual result was:

<p id="date"></p>

So somehow the formated_date variable was being defined, but was empty…

Except it wasn’t.

I printed out the variable in the context dictionary just before rendering and saw the correct dates displayed for each post.

The Weird Part¶

So far this is just a typical annoying bug story. Here’s the weird part:

I opened the file directly by double clicking it in the build directory and the page showed up in the browser, with the date, even though it wouldn’t show up when browsing from the local server, which should have been the same file. Even this I would have been happy to attribute to some weird browser behaviour, or some weird behaviour of the python http server. I don’t know that much about web stuff in general so I can believe anything.

But here’s the thing. I closed the server and reopened it. Still the date didn’t show up. Weird. So then I literally typed:

cat path/to/post | less

and scrolled down to where the date should be. It still wasn’t there. Meanwhile, I have the very same file open in the browser and it is.

Then I go:

pushd path/to/
cat post | less

and sure enough, the date shows up!. Then:

popd
cat path/to/post | less

and it still shows up!

So what on earth was going on the first time I typed cat?!