# Linux shell crash course

## Part 1: why shell?
- is it too old?
- script stuff
- copy and paste explinations from others or stackoverflow
- Faster, once you get used to it
- Easy to program interfaces (as opposed to GUIs)
- We can't teach you shell, but we can show you some examples and you can explore yourselfves later.
- work with others!

## Part 2: crash course
https://scicomp.aalto.fi/scicomp/shell/

- General principles
- type in, see output
- command + options + arguments
- cp -i file1.txt file2.txt
- Success = quiet
- Files
- Files represented by names
- Directories separated by /
- Editing files
- Do you need to via shell? Sometimes
- nano
- C-x then y to exit
- less
- Some keystrokes to do things: q
- Listing, moving, copying
- ls , ls -l, ls -a, ls -la (=ls -l -a)
- mv
- cp
- warning: both of these will overwrite file with no warnings!
- rm, rm -
- mkdir
- Directories
- working directory
- pwd
- cd
- / and ~
- Manual pages
- man (same keystrokes as less)
- --help or -h
- example: how to make `rm` ask before removing a file?
- History and tab completion
- up arrow
- TAB
-
- Variables
- Environment and shell variables
- ABCD=value to set
- $ or ${} syntax to retrieve
- WORK=/home/rkdarst/project
- echo $WORK
- cd $WORK

## Part 3: what's next?

- ssh
- Use it for something (otherwise no purpose...)
- Operate on remote computer
- Connect things together
- Unix philosophy: many small connected tools
- grep | wc
- scripting
- You could say the whole point is to *do it many times*
- conditionals, loops
- if, then, else, for, case, etc
- math
- x=5, $((1 + $x))
- If you go too far, maybe shell isn't the right thing for you
- coustomization via .bashrc
- Other resources
-
- Linux shell scripting, focused on science: https://scicomp.aalto.fi/training/linux-shell-tutorial/