Automatic editing

For changing file contents, we often use editors. But sometimes it is a good idea to do this from a script and do a change to many files at once or do the same kind of changes often. The classic approach to this is using sed, which is made exactly for this purpose. But most …

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vim and vi

We all have our preferences for editors and IDEs. I like Emacs and IntelliJ. But I also like vi. When you work on Linux-Servers that are not your own, there is a certain, quite limited set of software installed, that makes this thing work. Usually you will find Perl and Python. And vi as editor. …

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Unit and Integration Test with Databases

From an ideological point of view, tests that involve the database may be unit tests are may be integration tests. For many applications the functional logic is quite trivial, so it is quite pointless to write „real unit tests“ that work without the database. Or it may be useful. But there is a category of …

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Git for Linux System Engineering

Now that git has become the standard version control software, which is used by software developers. Now for system engineering and system administration purposes it used to be an approach to just login and do something and remember it or even note it somewhere. Some people tried to just use RCS or SCCS on the …

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Starting processes while booting (Linux)

When a Linux system is booted, we want certain processes to run immediately. In the old days, that is 25 years ago or so, this was done in „BSD-style“ by having certain magical shell scripts that start everything in the right order. When adding another service, this just had to be added to the shell …

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Ansible

We are talking about system administration and system engineering for Linux. Most of this also works more or less the same on Unix, but this is today much less relevant. It is even possible to do some of these things on MS-Windows, but that is another story… So just assume for the time being OS=Linux. …

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How to disable touchpad (on Linux/X11)

For me it is much better to use an external mouse than the touchpad, which I sometimes touch accidentally. So, here is how to disable it with a short Perl-Script. A bash script with a bit of Perl would do the same, btw. #!/usr/bin/perl my $tp = `xinput list | egrep -i touch`; chomp $tp; …

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How to rename files according to a pattern

We often encounter situations, where a large number of files should be copied or renamed or moved or something like that. This can be done on the Linux command line, but it should be possible in almost the same way on the Unix/Linux/Cygwin-command line of newer MS-Windows or MacOS-X. Now people routinely do that and …

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Unicode and C

It is a common practice in C to use arrays of char as strings. The 0 is used as end marker. The whole thing was created like that in the 1970s and at that time it was kind of cool to get away with one less language feature and to express it in terms of …

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Tips and Tricks: Typing Unicode

I found this on netzwolf.info: You can enter arbitrary Unicode characters (more precisely code points) in X11 on Linux, if you know their Hex-Code: Press Shift-Ctrl (keep them pressed) Press also the letter u Release the Ctrl-Key Release the u-key Keep the Shift-key pressed Enter the Hex-Code of the Code point with the number of …

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