Session 2
Get to know your computer
Adrian Demleitner 
Demleitner Taught by Adrian Demleitner. Possibly with further colleagues.
In this session
- The command line
- Paths — absolute, relative, and why your script cannot find the file
- Data storage — what actually happens when you save something
Bring your laptop. Everything in this session happens on your own machine.
The command line
- Terminal, shell, prompt: what each word means
- Where you are:
pwd,ls/dir,cd - Making and moving things:
mkdir,cp,mv,rm— and whyrmdeserves respect - Looking inside files without opening them:
cat,head,less - Finding things:
grep,find - Pipes and redirection:
|,>,>>— combining small tools into a large one - Getting help:
--help,man
WarningmacOS, Windows, Linux
The commands differ. On Windows, PowerShell and WSL behave differently again. We work through all three; find a neighbour on the same system.
Paths
- Absolute versus relative paths
.and.., the home directory~- Path separators, spaces in filenames, and why “Meine Arbeit Final (2).docx” causes trouble
- Extensions, and the fact that they are only a hint
- The
PATHvariable — why the computer sometimes says “command not found”
File naming conventions
A short set of rules that will save you hours later:
- No spaces, no umlauts, no special characters
YYYY-MM-DDfor dates, so that sorting by name sorts by time- Consistent, meaningful prefixes
- Version in the name only if you are not using version control — from next week, you are
Data storage
- Files and file systems, directories as a tree
- Bytes, encodings, and why a text file opens as gibberish (UTF-8, and everything before it)
- Plain text versus binary formats: which of your files can you still open in twenty years?
- Local, external, network, cloud — where “the file” actually is
- Backups: the 3-2-1 rule, and the difference between a backup and a sync
Exercise
Working entirely from the command line: create a project directory with a sensible structure, put a text file in it, find it again with find, search inside it with grep, and copy the result somewhere else. Then delete the whole thing and rebuild it — faster.
TipIn parallel in the Intro