Adventures & experiences in contemporary technology
In the BASH shell used on Linux and UNIX, the history command calls up a list of recent commands used and has many uses. There is a .bash_history file in the root of the user folder that logs and provides all this information so there are times when you need to exclude some commands from there but that is another story.
The Julia REPL environment works similarly to many operating system command line interfaces, so I wondered if there was a way to recall or refer to the history of commands issued. So far, I have not come across an equivalent to the BASH history command for the REPL itself but there the command history is retained in a file like .bash_history. The location varies on different operating systems though. On Linux, it is ~/.julia/logs/repl_history.jl while it is %USERPROFILE%\.julia\logs\repl_history.jl on Windows. While I tend to use scripts that I have written in VSCode rather than entering pieces of code in the REPL, the history retains its uses and I am sharing it here for others. In the past, the location changed but these are the ones with Julia 1.8.2, the version that I have at the time of writing.
Recently, I got to experimenting with Ansible after reading about the orchestration tool in a copy of Admin magazine. It came in handy for updating a few web servers that I have as well as updating my main Linux workstation. For the former, automated entry of SSH passwords sufficed but the same did not apply for sudo usage on my local machine. This meant that I needed to use Ansible Vault to store the administrator password and doing so opened up a file in the Vi editor. since I am not familiar with Vi and wanted to get things sorted quickly, I fancied using something more user-friendly like Nano.
Doing this meant adding the following line to .bashrc:
export EDITOR=nano
Saving and closing the file followed by reloading the session set me up for what was needed.
While I continue to use Spyder as my preferred Python code editor, I also tried out Visual Studio Code. Handily, this Integrated Development Environment also has facilities for working with R and Julia code as well as MarkDown text editing and adding the required extensions is enough for these applications; it helps that there is an unofficial Grammarly extension for content creation.
My Python code development makes use of the Pylance extension and it works a little differently from Spyder when it comes to including files using import statements. Spyder will look into the folder where the base script is located but the default behaviour of Pylance is that it looks in the root path of your workspace. This meant that any code that ran successfully in Spyder failed in Visual Studio Code.
The way around this was to add the required location using the python.analysis.extraPaths setting for the workspace. That meant opening Settings by navigating to File > Preferences > Settings in the menu system and entering python.analysis.extraPaths into the search box. That took me to the section that I needed and I then clicked on Add Item before entering the required path and clicking on the OK button. That was enough to fix the problem and all worked as it should after that.
One thing that is very handy for shell scripting is to have automated entry of passwords for logging into other servers. This can involve using plain text files, which is not always ideal so it was good to find an alternative. The first step is to use the keygen tool that comes with SSH. The command is given below and the -t switch specifies the type of key to be made, RSA in this case. There is the option to add a passphrase but I decided against this for sake of convenience and you do need to assess your security needs before embarking on such a course of action.
ssh-keygen -t rsa
The next step is to use the ssh-copy-id command to generate the keys for a set of login credentials. For this, it is better to use a user account with restricted access to keep as much server security as you can. Otherwise, the process is as simple as executing a command like the following and entering the password at the prompt for doing so.
ssh-copy-id [user ID]@[server address]
Getting this set up has been useful for running a file upload script to keep a web server synchronised and it is better to have the credentials encrypted rather than kept in a plain text file.
Custom error messages are good to add to SAS macros but you can get inconsistent colouration of the message text in multi-line messages. That was something that I just overlooked until I recently came across a solution. That is to use a hyphen at the end of the ERROR/WARNING/NOTE prefix instead of the more usual colon. Any prefixes ending on a hyphen are not included in the log text and the colouration ignores the carriage return that ordinary would change the text colour to black. The simple macro below demonstrates the effect.
Macro Code:
%macro test;
%put ERROR: this is a test;
%put ERROR- this is another test;
%put WARNING: this is a test;
%put WARNING- this is another test;
%put NOTE: this is a test;
%put NOTE- this is another test;
%mend test;
%test
Log Output:
ERROR: this is a test
this is another test
WARNING: this is a test
this is another test
NOTE: this is a test
this is another test
Recently, I tried using Commento with a static website that I was developing and this needed PostgreSQL rather than MySQL or MariaDB, which many content management tools use. That meant a learning curve that made me buy a book as well as the creation of a system account for administering PostgreSQL. These are not the kind of things that you want to be too visible so I wanted to hide them.
Since Linux Mint uses AccountsService, you cannot use lightdm to do this (the comments in /etc/lightdm/users.conf suggest as much). Instead, you need to go to /var/lib/AccountsService/users and look for a file called after the user name. If one exists, all that is needed is for you to add the following line under the [User] section:
SystemAccount=true
If there is no file present for the user in question, then you need to create one with the following lines in there:
[User]
SystemAccount=true
Once the configuration files are set up as needed, AccountsService needs to be restarted and the following command does that deed:
sudo systemctl restart accounts-daemon.service
Logging out should reveal that the user in question is not listed on the logon screen as required.
There is a simple principal with the 7G Firewall from Perishable press: it is a set of mod_rewrite rules for the Apache web server that can be added to a .htaccess file and there also is a version for the Nginx web server as well. These check query strings, request Uniform Resource Identifiers (URI’s), user agents, remote hosts, HTTP referrers and request methods for any anomalies and blocks those that appear dubious.
Unfortunately, I found that the rules heavily slowed down a website with which I tried them so I am going have to wait until that is moved to a faster system before I really can give them a go. This can be a problem with security tools as I also found with adding a modsec jail to a Fail2Ban instance. As it happens, both sets of observations were made using the GTmetrix tool so it seems that there is a trade off between security and speed that needs to be assessed before adding anything to block unwanted web visitors.
Every week, I get an email newsletter from Woody’s Office Watch. This was something to which I started subscribing in the 1990’s but I took a break from it for a good while for reasons that I cannot recall and returned to it only in recent years. This week’s issue featured a list of online paraphrasing tools that are part of what is offered by Quillbot, Paraphraser, Dupli Checker and Pre Post Seo. Each got their own reviews in the newsletter so I will just outline other features in this posting.
In Quillbot’s case, the toolkit includes a grammar checker, summary generator, and citation generator. In addition to the online offering, there are extensions for Microsoft Word, Google Chrome, and Google Docs. In addition to the free version, a paid subscription option is available.
In spite of the name, Paraphraser is about more than what the title purports to do. There is article rewriting, plagiarism checking, grammar checking and text summarisation. Because there is no premium version, the offering is funded by advertising and it will not work with an ad blocker enabled. The mention of plagiarism suggests a perhaps murkier side to writing that cuts both ways: one is to avoid copying other work while another is the avoidance of groundless accusations of copying.
It was appear that the main role of Dupli Checker is to avoid accusations of plagiarism by checking what you write yet there is a grammar checker as well as a paraphrasing tool on there too. When I tried it, the English that it produced looked a little convoluted and there is a lack of fluency in what is written on its website as well. Together with a free offering that is supported by ads that were not blocked by my ad blocker, there are premium subscriptions too.
In web publishing, they say that content is king so the appearance of an option using the acronym for Search Engine Optimisation in it name may not be as strange as it might as first glance. There are numerous tools here with both free and paid tiers of service. While paraphrasing and plagiarism checking get top billing in the main menu on the home page, further inspection reveals that there is a lot more to check on this site.
In writing, inspiration is a fleeting and ephemeral quantity so anything that helps with this has to be of interest. While any rewriting of initial content may appear less smooth than the starting point, any help with the creation process cannot go amiss. For that reason alone, I might be tempted to try these tools from time to time and they might assist with proof reading as well because that can be a hit and miss affair for some.
My response to changes in the technology stack used in clinical research is to develop some familiarity with programming and scripting platforms that complement and compete with SAS, a system with which I have been programming since 2000. One of these has been R but Python is another that has taken up my attention and I now also have Julia in my sights as well. There may be others to assess in the fullness of time.
While I first started to explore the Data Science world in the autumn of 2017, it was in the autumn of 2019 that I began to complete LinkedIn training courses on the subject. Good though they were, I find that I need to actually use a tool in order to better understand it. At that time, I did get to hear about Python packages like Pandas, NumPy, SciPy, Scikit-learn, Matplotlib, Seaborn and Beautiful Soup though it took until of spring of this year for me to start gaining some hands-on experience with using any of these.
During the summer of 2020, I attended a BCS webinar on the CodeGrades initiative, a programming mentoring scheme inspired by the way classical musicianship is assessed. In fact, one of the main progenitors is a trained classical musician and teacher of classical music who turned to Python programming when starting a family so as to have a more stable income. The approach is that a student selects a project and works their way through it with mentoring and periodic assessments carried out in a gentle and discursive manner. Of course, the project has to be engaging for the learning experience to stay the course and that point came through in the webinar.
That is one lesson that resonates with me with subjects as diverse as web server performance and the ongoing pandemic pandemic supplying data and there are other sources of public data to examine as well before looking through my own personal archive gathered over the decades. Some subjects are uplifting while others are more foreboding but the key thing is that they sustain interest and offer opportunities for new learning. Without being able to dream up new things to try, my knowledge of R and Python would not be as extensive as it is and I hope that it will help with learning Julia too.
In the main, my own learning has been a solo effort with consultation of documentation along with web searches that have brought me to the likes of Real Python, Stack Abuse, Data Viz with Python and R and others for longer tutorials as well as threads on Stack Overflow. Usually, the web searching begins when I need a steer on a particular or a way to resolve a particular error or warning message but books always are worth reading even if that is the slower route. Those from the Dummies series or from O’Reilly have proved must useful so far but I do need to read them more completely than I already have; it is all too tempting to go with the try the “programming and search for solutions as you go” approach instead.
To get going, many choose the Anaconda distribution to get Jupyter notebook functionality but I prefer a more traditional editor so Spyder has been my tool of choice for Python programming and there are others like PyCharm as well. Spyder itself is written in Python so it can be installed using pip from PyPi like other Python packages. It has other dependencies like Pylint for code management activities but these get installed behind the scenes.
The packages that I first met in 2019 may be the mainstays for doing data science but I have discovered others since then. It also seems that there is porosity between the worlds of R an Python so you get some Python packages aping R packages and R has the Reticulate package for executing Python code. There are Python counterparts to such Tidyverse stables as dply and ggplot2 in the form of Siuba and Plotnine, respectively. The syntax of these packages are not direct copies of what is executed in R but they are close enough for there to be enough familiarity for added user friendliness compared to Pandas or Matplotlib. The interoperability does not stop there for there is SQLAlchemy for connecting to MySQL and other databases (PyMySQL is needed as well) and there also is SASPy for interacting with SAS Viya.
Pyhton may not have the speed of Julia but there are plenty of packages for working with larger workloads. Of these, Dask, Modin and RAPIDS all have there uses for dealing with data volumes that make Pandas code crawl. As if to prove that there are plenty of libraries for various forms of data analytics, data science, artificial intelligence and machine learning, there also are the likes of Keras, TensorFlow and NetworkX. These are just a selection of what is available and there is no need not to check out more. It may be tempting to stick with the most popular packages all the time, especially when they do so much, but it never hurst to keep an open mind either.
During the summer, I discovered that Firefox was steadfastly opening on the same virtual desktop on Linux Mint (the Cinnamon version) regardless of the one on which it was started. Being a creature of habit who routinely opens Firefox within the same virtual desktop all the time, this was not something that I had noticed until the upheaval of a system rebuild. The supposed cause is setting the browser to reopen tabs from the preceding session. The settings change according to the version of Firefox but it is found in Settings > General in the version in which I am writing these words (Firefox Developer Edition 94.0b4) and the text beside the tick box is Open previous windows and tabs.
While disabling the aforementioned setting could work, there is another less intrusive solution. This needs the opening of a new tab and the entering of the address about:config in the address bar. If you see a warning message about the consequences of proceed further, accept responsibility using the interface as you do just that. In the resulting field marked Search preference name, enter the text widget.disable-workspace-management and toggle the setting from false to true in order to activate it. Then, Firefox should open on the desktop where you want it and not some other default location.