Exercise "posix"

1. Get yourself an access to a POSIX system. There are several options:
   1. Ubuntu. Install it either directly on your laptop (the default and supported option) or in a virtual machine (VirtualBox is a popular hypervisor). The latest long term support version of Ubuntu is 20.04.
   2. Most of other Linux-based systems like Debian or Fedora (but not Android) will do just as well. Some minor details might differ from Ubuntu.
   3. MacOS with homebrew. Some details are different from Ubuntu.
   4. Microsoft Windows with Windows Subsystem for Linux. You can apparently install Ubuntu from Windows-App-Store and run it as an app within your Windows box. Here is the manual from Microsoft: [https://docs.microsoft.com/en-us/windows/wsl/].
   5. Microsoft Windows with Cygwin. Cygwin should also work on older (and 32-bit) versions of Windows.
   6. Android with termux. No csharp in its repository though.
   7. An account on a POSIX server and a laptop to ssh to your account. You might need to manually install some packages though.
2. Learn how to start a terminal in your POSIX system. Here is a tutorial for Ubuntu.
3. Read about the man utility. Run man man and read the description of the utility in your system.
   Hints: man usually uses less as the default pager; you quit from less by pressing the q-key.
4. Learn the following commands (file utilities) from the GNU Core Utilities: cp, ls, mkdir, mv, rm, and the bash built-in command cd.
   Hints: type, for example, man cp in your terminal; Google-search "man cp".
5. Read about the command-line completion.
6. Install your favourite text editor. If you don't have one, install the Nano text editor with the command
   sudo apt install nano
7. Install also the vim editor, sudo apt install vim, should you ever want me to look at your files.
8. Learn to create, save, and edit text files with your favourite text editor.
9. Answer questions-intro.