It would seem that I have not got around to writing a post on control operators in bash, so today I will be writing a thing or two about this little aspect of bash scripts, and working with in a Command Line Interface in Linux. Control operators are just one of many little details that one will need to learn a thing or two about in order to become more professional with bash, and operating system automation tasks in Linux systems by way of bash scripts.

There are three general things to be aware of when it comes to this, one is to end a command, and start a new one which can be done with a semicolon (\;). Another thing to be aware of is to use (&&) as a way to run another command after a command, but only if the first one ends with a status code of zero. There is then using the (||) control operator if I want to run another command, but only if the command before it failed or for one reason or another exited with a non zero exit code status.

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I have a lot of pots boiling when it comes to things to learn and research more, one of which is to become more competent when it comes to working with a Linux system. A major part of doing so is to learn a hold lot more about bash, and with that that bash built in commands once of which is the Linux test bash built in command.

In a previous Linux post on bash scripts I wrote about special parameters one of which is the \$\? parameter. This parameter will give the exit status of the last command that was called in the shell. With that said what the test command does is it, well, preforms some kind of test and then will exit with a status code of 0 if all goes well with that test, else it will exit with 1.

The test command by itself will not produce any output to the standard output of the bash console, so often it should be used in conjunction with a other commands and bash features with the special parameter that contains the exit status to produce some kind of output. However often when the test command is used it is when making bash scripts and thus it is just used as a way to make some kind of choice when it comes to doing something or not, as such that is likely why it will not produce any output unless something is done to make it do so.

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In todays post on Linux commands I will be going over a few quick examples of the Linux ln command that is used to create soft and hard links to files and folders in a Linux system. Say you are in a situation in which you have some kind of actual resource in one location, but you also want to have the same resource in another location in the same file system. One way would be to use the Linux cp command to just make one or more copies of the resource I suppose, however there are some draw backs to this. For one thing I edn up with redundant copes of the same resource. Another draw back is that if I make changes to the original copy of the resource that will not effect the copy. In some cases I guess that is a good thing as that is one of the major reason why to make a copy of something after all, however what if I want to just make a link to the same resource at another location? The way to do so in Linux would be to make a hard or soft link.

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Today I would like to write about a topic that I have been putting off for too long which is how to go about having more than one binary of nodejs to work with in Raspberry Pi OS. When first setting up a clean image of raspberry pi os one of the first things I would like to do is install nodejs, and the typical way of doing so would be to just install whatever version of nodejs there is to work with by way of apt. The problem with doing this though is that the version of nodejs is often very out of date, in fact as of this writing it is a version of nodejs that is no longer supported. Also often I might want to have more than one version of nodejs installed actually, and have a way to switch between them. For example I might want to write a script that I want to work on a wide range of nodejs versions, going as far back as say maybe nodejs 8.x. So then I would want to test out the script on nodejs 8.x, 9.x, 10.x, …, 16.x as such I would need to have some way to not just have an up to date version of nodejs when it comes to the latest version, I would also want the latest version of each major release going back to whatever point I want to push backward compatibility to.

So then in this post I will be going over one way to go about having two or more nodejs binaries to work with in a Raspberry pi os environment.

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This week I put together a quick simple build tool solution that I might used in one or more of my nodejs projects. There are of course many popular projects that are this kind of tool that I could just use and move on with, but some times I do just like to make my own solutions for things.

There are at least two general features that I think a build tool should do when making some kind of javaScript project. One feature is to just simply concatenate two or more source code files into a single string value and write that string file to a development form of a final package of the project. The other major feature is to do more or less the same as the first feature only to produce a minified version of the development form of the file. The first major feature is simple enough, all I have to do is loop over an array of relative paths to source code files to create a single string and then write that file. However the second feature is a little not so simple and will require some kind of library for minifying javaScript code.

Although I do tend to try to avoid using external user space projects when it comes to this series of nodejs examples, I have not got around to making my own simple javaScript tokenizer, let alone any kind of project that will minify javaScript code. At some point in the future I might get around to making my own project for that sort of thing, and try to keep it simple but for now I think I am going to have to just go with some kind of user space option.

A few years back I wrote a post on a user space package for this sort of thing called jsmin, which is a tired yet true solution for minifying javaScript. It looks as though this project is not being maintained though as nothing has changed with the source code for over ten years. I am the kind of person that understands that that is not always such a bad thing, some times you have a project that is pretty darn solid, and still works great for a certain kind of task. However I decided to go with another popular well known option for this called uglify.js.

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