Linux-Fu: Automation For Chrome And The Desktop By Matching Screenshots

June 15, 2020 by Al Williams 11 Comments

I will be the first to admit it. This is almost not — at least not specifically — a Linux article. The subject? An automation tool for Chrome or Firefox. But before you hit the back button, hear me out. Sure, this Chrome plugin started out as a tool to automatically test web pages and automate repetitive tasks in the browser. However, it can extend that power to all programs on your computer. So, in theory, you can use it to graphically build macros that can interact with desktop applications in surprisingly sophisticated ways. In theory, anyway; there are a few problems.

The program has a few different names. Most documentation says UI Vision RPA, although there are some references to Kantu, which appears to be an older name. RPA is an acronym for Robotic Process Automation, which is an industry buzz word.

Let’s take it for a spin and see what it’s all about.

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Linux Fu: Raspberry Pi Desktop Headless

June 1, 2020 by Al Williams 32 Comments

It seems to me there are two camps when it comes to the Raspberry Pi. Some people use them as little PCs or even laptops with a keyboard and screen connected. But many of us use them as cheap Linux servers. I’m in the latter camp. I have probably had an HDMI plug in a Pi only two or three times if you don’t count my media streaming boxes. You can even set them up headless as long as you have an Ethernet cable or are willing to edit the SD card before you boot the machine for the first time.

However, with the Raspberry Pi 4, I wanted to get to a desktop without fishing up a spare monitor. I’ll show you two ways to get a full graphical KDE desktop running with nothing more than a network connection.

The same principle applies to most other desktop environments, but I am using KDE and Ubuntu on the Pi, even though something lighter would probably perform better. But before we get there, let’s talk about how X11 has had a big identity crisis over the years.

The Plan

There are many ways to remotely access X programs, many of which are rarely used today. However, for this purpose, we are going to use SSH tunneling along with some special tricks to get the entire desktop running. It is easy to just run a single X program over SSH, and you’ve probably done that often. If so, you can skip to the next section.

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Linux Fu: Alternative Shells

May 21, 2020 by Al Williams 38 Comments

On Unix — the progenitor of Linux — there was /bin/sh. It was simple, by comparison to today’s shells, but it allowed you to enter commands and — most importantly — execute lists of commands. In fact, it was a simple programming language that could make decisions, loop, and do other things to allow you to write scripts that were more than just a list of programs to run. However, it wasn’t always the easiest thing to use, so in true Unix fashion, people started writing new shells. In this post, I want to point out a few shells other than the ubiquitous bash, which is one of the successors to the old sh program.

Since the 7th Edition of Unix, sh was actually the Bourne shell, named after its author, Stephen Bourne. It replaced the older Thompson shell written in 1971. That shell had some resemblance to a modern shell, but wasn’t really set up for scripting. It did have the standard syntax for redirection and piping, though. The PWB shell was also an early contender to replace Thompson, but all of those shells have pretty much disappeared.

You probably use bash and, honestly, you’ll probably continue to use bash after reading this post. But there are a few alternatives and for some people, they are worth considering. Also, there are a few special-purpose shells you may very well encounter even if your primary shell is bash.

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ZRAM Boosts Raspberry Pi Performance

May 20, 2020 by Al Williams 18 Comments

Linux is a two-edged sword. On the one hand, there’s so much you can configure. On the other hand, there’s so much you can configure. It is sometimes hard to know just what you should do to get the best performance, especially on a small platform like the Raspberry Pi. [Hayden James] has a suggestion: enable ZRAM and tweak the kernel to match.

Although the post focuses on the Raspberry Pi 4, it applies to any Linux system that has limited memory including older Pi boards. The idea is to use a portion of main memory as a swap file. At first, that might seem like a waste since you could use that memory to, you know, actually run programs. However, the swap devices are compressed, so you get more swap space and transfers from these compressed swap devices and main memory are lightning-fast compared to a hard drive or solid state disk drive.

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New Breakout Board For Grid-EYE Thermal Sensor

May 18, 2020 by Donald Papp 13 Comments

Panasonic’s Grid-EYE sensor is essentially a low-cost 8×8 thermal imager with a 60 degree field of view, and a nice breakout board makes it much easier to integrate into projects. [Pure Engineering] has created an updated version of their handy breakout board for the Grid-EYE and are currently accepting orders. The new breakout board is well under an inch square and called the GridEye2 (not to be confused with the name of the main component, the AMG8833 Grid-EYE by Panasonic.)

GridEye2 connected to CH341A dev board, allowing easy PC interface over USB.

A common way to interface with the Grid-EYE is over I2C, but to make connecting and developing on a PC more straightforward, [Pure Engineering] has made sure the new unit can plug right into their (optional) CH341A development board to provide a USB interface. Getting up and running on a Linux box is then as simple as installing the Linux drivers for the CH341A, and using sample C code to start reading thermal data from an attached GridEye2 board.

The Grid-EYE is a low-cost and capable little device that mates well with an LED matrix display, and on the more advanced side, a simple Gaussian interpolation can have a striking effect when applied to low-resolution sensors, making them appear higher resolution than they actually are.

Linux Command Line Productivity With Tmux

May 1, 2020 by Al Williams 23 Comments

It is no secret that most Linux power users use the shell for many tasks, as for people who know what they are doing, it can be quite efficient. In addition, there are some tasks that can only be carried out from the command line, although their number shrinks every year. However, these days we are spoiled because you can have one X session running lots of terminals at once. If you log into a server, it might not have X. Or you might log into a computer over a slow connection where X is painful to use. What then? The modern answer is the tmux terminal multiplexer, and [zserge] has a thoughtful introduction to how you can use tmux for improved productivity at the command line.

In particular, he shares some configuration and offers sound advice. For example, do you really need a status bar that shows you CPU load at all times? Cool, yes, but not always a practical win.

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Beam Your Program To Another Computer

April 28, 2020 by Al Williams 53 Comments

If you’ve programmed much in Linux or Unix, you’ve probably run into the fork system call. A call to fork causes your existing process — everything about it — to suddenly split into two complete copies. But they run on the same CPU. [Tristan Hume] had an idea. He wanted to have a call, telefork, that would create the copy on a different machine in a Linux cluster. He couldn’t let the idea go, so he finally wrote the code to do it himself.

If you think about it, parts of the problem are easy while others are very difficult. For example, creating a copy of the process’s code and data isn’t that hard. Since the target is a cluster, the machines are mostly the same — it’s not as though you are trying to move a Linux process to a Windows machine.

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