To set up a simple systemd timer as a user on Debian 9.9, here are the following steps to make it work.
Systemd version :
As a user, both the .service unit and .timer unit must be located in $HOME/.config/systemd/user.
If this folder does not exist, create it :
mkdir -p $HOME/.config/systemd/user
If both the .service and .timer files are named as test, it must be enabled and started :
systemctl --user enable test
systemctl --user start test
The expected output should be found using journalctl :
Using systemd as a user
[:ne binary operator expected
In addition to the explanation here, this error pops up when comparing two values.
Pay attention either comparing is about comparing two strings or two numeric values.
As a reminder :
val1 -eq val2
val1 -ne val2
val1 -ge val2
val1 -gt val2
val1 -le val2
val1 -lt val2
val1 = val2
val1 != val2
Further readings :
What is java.awt.headless ?
As well detailed in the article below,
Java contains a lot of classes which assume that there is a some sort of display and a keyboard attached. Sometimes, you are writing code to run on a server which does not have these and this is called Headless mode
For some Java-based web applications, graphics can be generated. Either you need to configure the application to use the local X Window server or use the Java Headless option.
Source : https://blog.idrsolutions.com/2013/08/what-is-headless-mode-in-java/
Use case example for headless image processing : https://github.com/processing/processing/wiki/Running-without-a-Display
If you need to run a job once, at is the tool perfectly suited for this need.
The at tool requires some options to run a job at a given moment.
Without any parameters, at pops up the following error :
The job can be either specified from the at prompt or using the -f
Here is an example to run a job in a minute from the time the command at is executed :
at now + 1 minute
at>echo "This is a test"
at now + 1 minutes
at>echo "This is a test"
Using a text file :
at now + 1 minute -f job_file
Once the job is completed, an email is sent. Check your local Mailbox using the mail command.
Good tutorials around at providing additional examples :
Here is a good article about Bash lowercase and uppercase possible operations :
Bash strings operations from Linuxhint
If you are using pandoc as a document converter from markdown to html, you may have this warning message while using the -s (–standalone) option.
[WARNING] This document format requires a nonempty title element.
Please specify either ‘title’ or ‘pagetitle’ in the metadata.
For more details about adding metadata information to your pandoc command line : https://pandoc.org/MANUAL.html#option–metadata
For example, if you want to produce an HTML file from a markdown file, the -s option uses a default template that only sets the header and the footer.
No html-based title is generated unless you explicitly request it using the -M option that sets the title metadata info.
pandoc -s -f gfm -t html -M title:Test -o test.html test.md
More info on the -s / –standalone option
Understanding and manipulating character sets encoding can not be underestimated.
Here are a few interesting Unicode primers found on the Internet :