just do git — shell

![gnugen logo](assets/gnugen_white_trans.svg)
# just do *git* — *shell*

*Introduction*

## Please help us improve!

There will be a short survey at the end of the presentation

## Table of contents

* [About gnugen](#/about-gnugen)
* [UNIX Shell — introduction](#/shell-intro)
* [UNIX Shell — beyond the basics](#/shell-beyond)
* [Some practice](#/some-practice)

---

# About gnugen

## Who are we?

![gnugen logo](assets/gnugen_white_trans.svg)

Promote free/libre software on the EPFL campus

## free/libre software

### Four fundamental freedoms

*  freedom to use: freely run parts of a program or not
*  freedom to study the source code
*  freedom to share the program
*  freedom to improve the program

## free/libre software

### But why?

*  Respect for the user
*  Accessible, inclusive
*  Privacy
*  Many more...

## what does that mean for me?

*  Events (Just do Git)
*  Want to talk about free software? We have Matrix / Telegram chat rooms
*  Need help installing Linux or with other free software?

---

# UNIX Shell introduction

## UNIX Shell (Terminal)

### Why do we need to learn how the shell works?

*  Language to interact with the computer
*  Git is a command line (cli) tool
*  Important: The Unix shell is not the same as PowerShell!

## UNIX Shell (Terminal)

### What is a command?

*  A command is just an application
*  Execute commands using the following format

```sh
alain@gnugen:~ $ command argument1 argument2 ...
```

here the command "command" is being executed with "argument1" and "argument2" as arguments

## UNIX Shell (Terminal)

### Flags and arguments

*  Flags are special arguments, that some cli applications support, they are optional

```sh
alain@gnugen:~ $ command --name alain argument1 ...
```

*  here the command "command" is being executed with the argument "argument1" and the flag "name" using "alain" as an argument

## UNIX Shell (Terminal)

### A command is a program

```sh
alain@gnugen:~ $ sudo apt install firefox
```

```sh
alain@gnugen:~ $ firefox
```

*  and Firefox opens 🔥

## UNIX Shell (Terminal)

### The three most important commands

*  <code>pwd</code> (print working directory) — show in which directory you currently are
*  <code>ls</code> (list) — show contents of the directory we are currently in
*  <code>cd</code> (change directory) — change into another folder

## UNIX Shell (Terminal)

### Where am I?

```sh
alain@gnugen:~ $ pwd
/home/alain
```

*  <code>~</code> is a shortcut for your home directory (<code>/home/alain</code>)

## Useful commands

### Which files are in this directory?

```sh
alain@gnugen:~ $ ls
Documents Downloads Music Pictures Videos
```

```sh
alain@gnugen:~ $ ls Documents/
EPFL 'random stuff' Notes.txt
```

```sh
alain@gnugen:~ $ ls -a Documents/
. .. .a-secret.file EPFL 'random stuff' Notes.txt
```

## Useful commands

### Step into and out of a directory

```sh
alain@gnugen:~ $ cd
```

```sh
alain@gnugen:~ $ cd Documents
```

```sh
alain@gnugen:Documents $ cd ../
```

## Filesystem paths

Absolute paths start at <code>/</code>, relative paths start from where you are

```sh
# absolute (from anywhere)
alain@gnugen:~ $ cd /home/alain/myfreesoftwareproject
```

```sh
# relative (from your home directory /home/alain)
alain@gnugen:~ $ cd myfreesoftwareproject
```

```sh
# relative
alain@gnugen:Pictures $ cd ../Documents
```

## Useful commands

### Create a new folder/directory

```sh
alain@gnugen:~ $ mkdir newfreesoftwareproject
```

```sh
alain@gnugen:~ $ ls
Documents Downloads Music newfreesoftwareproject Pictures Videos
```

```sh
alain@gnugen:~ $ cd newfreesoftwareproject
```

## Useful commands

### Copy files

```sh
alain@gnugen:~ $ cp Documents/Notes.txt CopyOfNotes.txt
```

```sh
alain@gnugen:~ $ ls
CopyOfNotes.txt Documents Downloads Music newfreesoftwareproject Pictures Videos
```

## Useful commands

### Rename/move files

```sh
alain@gnugen:~ $ mv CopyOfNotes.txt NewNotes.txt
```

```sh
alain@gnugen:~ $ ls
Documents Downloads Music newfreesoftwareproject NewNotes.txt Pictures Videos
```

```sh
alain@gnugen:~ $ mv NewNotes.txt Documents/NewNotes.txt
```

```sh
alain@gnugen:~ $ ls Documents/
EPFL 'random stuff' NewNotes.txt Notes.txt
```

## Useful commands

### Delete files

```sh
alain@gnugen:~ $ rm Documents/NewNotes.txt
```

```sh
alain@gnugen:~ $ ls Documents/
EPFL 'random stuff' Notes.txt
```

*  ⚠ no trash bin ⚠ think before you delete something ;)

## Text editors

*  <code>nano</code> — simple, great for beginners
*  <code>vim</code> — powerful, available everywhere
*  many more...

## Tips & tricks

*  Tab completion: complete filenames and paths with <code>tab</code>
*  <code>↑</code> / <code>↓</code>: browse your previous commands
*  <code>ctrl + r</code>: search through the commands you already used
*  <code>ctrl + c</code>: stop the command that is currently running

## UNIX Shell (Terminal)

### Getting help

*  <code>man ls</code> — the manual of a program (Linux / macOS, not in Git Bash)
*  <code>ls --help</code> — quick help, also works in Git Bash
*  full-screen programs (like <code>man</code>) are quit with <code>q</code>

---

# UNIX Shell beyond the basics

## UNIX Shell (Terminal)

### Pipes

*  the output of one command can be the input of the next one — chain them with <code>|</code>

```sh
alain@gnugen:~ $ ls | wc -l
6
```

*  here <code>ls</code> lists your files and <code>wc -l</code> counts the lines

## UNIX Shell (Terminal)

### Redirection

*  send output into a file with <code>></code> (overwrite) or <code>>></code> (append at the end)

```sh
alain@gnugen:~ $ echo "hello!" > hello.txt
alain@gnugen:~ $ cat hello.txt
hello!
```

```sh
alain@gnugen:~ $ echo "again" >> hello.txt
alain@gnugen:~ $ cat hello.txt
hello!
again
```

## UNIX Shell (Terminal)

### Permissions

*  every file has permissions: who may read, write or execute it

```sh
alain@gnugen:~ $ ls -l
-rw-r--r-- 1 alain alain 132 Oct 4 12:00 Notes.txt
-rwxr--r-- 1 alain alain 1024 Oct 4 12:10 backup.sh
```

*  <code>r</code>ead, <code>w</code>rite, e<code>x</code>ecute — once for the user, once for the group, once for everyone else

## UNIX Shell (Terminal)

### Variables

*  variables are defined in the running session and are read with <code>$</code>

```sh
alain@gnugen:~ $ name="alain"
alain@gnugen:~ $ echo $name
alain
```

## UNIX Shell (Terminal)

### Environment variables

*  environment variables are shared with every program you start

```sh
alain@gnugen:~ $ echo $SHELL
/bin/bash
```

```sh
alain@gnugen:~ $ env
SHELL=/bin/bash
HOME=/home/alain
[...]
```

## UNIX Shell (Terminal)

### Errors and return codes

*  commands can print feedback — no print usually means success
*  every command also returns a code: check it with <code>$?</code>

```sh
alain@gnugen:~ $ rm doesnotexist
rm: cannot remove 'doesnotexist': No such file or directory
```

```sh
alain@gnugen:~ $ echo $?
1
```

*  <code>0</code> = success, anything else = error

---

# Some practice

## Workshop

*  open the terminal on your computer
*  We have some exercises under <a href=https://gnugen.ch/en/guides/just-do-git-shell>gnugen.ch/guides</a>

---

# But first

# Thank you!

---

## just do *git* — *shell*

Slides, guides and workshop are available on [gnugen.ch/en/guides](https://gnugen.ch/en/guides/)

Survey: