Linux/Unix

I was looking to add GPS to my Raspberry Pi (specifically the Clockwork uConsole) and found this USB GPS Receiver with 2m Extension Cable on the PiHut website.

The unit has a USB interface, a 2 meter long cable, and the GPS receiver itself is magnetic and so can attach to lots of different surfaces. Plus, since it was sold on the PiHut website I was quite confident that it would be easy to get working with the Raspberry Pi. As it happens, it was easy to get working, I just needed to install a couple of extra tools to make sure it was producing the correct data.

In this article we'll look at what happens when you plug in the GPS receiver, and then look at a couple of packages you can use to verify that the GPS receiver is working correctly. This assumes that you are running the latest version of Raspberry Pi OS.

I work on a couple of ThinkPad laptops (T490 and a P14s) and whilst they have fingerprint scanners I haven't really considered using them. I once attempted to get a fingerprint scanner working in Linux on an old HP laptop and that experience put me off trying again.

When I looked into the getting the fingerprint scanner working on a ThinkPad with Pop! OS installed it turned out to be quite easy. The drivers were already present so it was just a case of installing the correct software and adding my settings.

Timing web requests is possible in curl using the -w or --write-out flag. This flag takes a number of different options, including several time based options.

These timing options are useful for testing the raw speed of requests from a web server and can be an important tool when improving performance and quickly getting feedback on the response.

The -w or --write-out flag in curl has a number of different options, far more than I can add here. You can use these options by surrounding them in a "%{parameter}" structure and passing this as a string to the -w flag.

I was typing on my Keychron K2 keyboard today and realised that I hadn't used the function keys at all. Not that I hadn't tried a few times, it's just that the function keys were linked to the media keys for the laptop I was using. When I pressed the F2 key it would increase the screen brightness, which was fine, but I realised that I had missed using the function keys for a while.

I was using Ubuntu 20.04 and there appeared to be no option to turn this off in the settings. After a little research I found a solution to the problem.

In Linux, creating a symlink is a common way of ensuring that the directory structure of a deployment will always be the same. For example you might create a symlink so that the release directory of release123/docroot will instead be just current. This is done using the ln command in the following way, the -s flag means that we use the ln (aka link) command to create a symbolic link.

I'm a proponent of automation, so when I find myself running the same commands over and over I always look for a way of wrapping that in an alias or script.

I spend a lot of my day to day job in the command line and I realised today that I must have typed 'git status' for the millionth time and wondered what my most commonly used commands were. So I found a stack overflow post showing my most used commands in a nice little bash one liner.

history | awk '{CMD[$2]++;count++;}END { for (a in CMD)print CMD[a] " " CMD[a]/count*100 "% " a;}' | grep -v "./" | column -c3 -s " " -t | sort -nr | nl |  head -n10

This command extracts information from the bash history and shows me the root command I have run. This showed me the following on my current system.

Grep is a really powerful tool for finding things in files. I often use it to scan for plugins in the Drupal codebase or to scan through a CSV or log file for data.

For example, to scan for user centric ViewsFilter plugins in the Drupal core directory use this command (assuming you are relative to the core directory).

grep "@ViewsFilter(\"user" -r core

The -r flag here recursively scans the 'core' directory. This command returns the following output.

Part of the process of putting a new site live can be moving DNS entries around. Prior to doing this it's a really good idea to sort out the Time To Live (TTL) of the DNS record so that when you do change DNS entries you aren't waiting around for a day for the DNS to sort itself out. Most DNS registrars will allow you to set your TTL down to a minute or so.

It's also very important to check the status of your DNS records to ensure that they have the correct TTL, usually a day before (and day of) the move.

You can check the TTL value of your A record with the host command. Change the value of the -t (type) flag to aaaa or cname to inspect different types of records.

host -a -t a www.hashbangcode.com

This will produce the following output. The TTL of the domain below is '125'.

Whilst it is possible to view the contents of an SSL cert from within most modern browsers I occasionally find the need to use the command line to find out the same information. I find this useful when renewing certificates as browsers can occasionally cache certificates for longer than expected, causing false results.

DNS records, as many of you will already know, are commonly used to translate a human readable address into an IP address. This means that instead of visiting a website by typing in it's IP address you can just type in the easy to remember DNS address. I won't talk too much about how DNS records work here, but if you want to know more then you can read the awesome and easy to understand how DNS works commic.

In this post I will be looking at different tools that can be used to find out more about a DNS record, and what kinds of results they return. I won't be looking at the tools in great detail, but enough to get you started when looking up DNS records.