Linux basics

If you are looking for the manual in Polish, you will find it here.

Survival

From GUI to Terminal:
From terminal to GUI:
```
ls
xdg-open .
```

Explore your home directory:

#
ls

# $HOME stores
# path to your home directory
ls $HOME

echo $HOME

Survival 1 - where am i? Why I get No such file or directory or Permission denided? Twese two commands will help you:
```
pwd

ls
```

Survival 2 - how can I come back to my home directory?

# main directory in linux is: /  the same as C: in Windows
cd /
pwd

# come back home with one command
cd

# let's do it again
cd /
pwd
ls

# ~ means my home directory
# change the directory to ~
cd ~

Before learning how to work with directories, let's install tree:
```
sudo apt-get update
sudo apt install tree
```
Sudo? We have xkcd for that!.

Working with the directories:

mkdir poland
cd poland
mkdir cities
cd cities
mkdir gdansk
ls
mkdir warszawa
mkdir wroclaw
mkdir krakow
ls
cd ..
pwd
cd ..

tree

tree ../poland

You should see:

poland
\- cities/
   |- gdansk/
   |- warszawa/
   |- wroclaw/
   \- krakow/

Traverse the directories cd PATH:

# go in
pwd
cd cities/krakow
pwd

# go out
cd ../..

Notice:
```
ls cities
ls /home/
ls ~
```

Please add a directory villages that contains directories for small settlements in Poland:

poland
 |- cities/
 |   |- gdansk/
 |   |- krakow/
 |   |- warszawa/
 |   \- wroclaw/
 |
 \- villages/
    |- nowawies
    \- starawies

Survival 3 - vim:
- install vim:
```
sudo apt-get install vim
```
- go back to your home dir: cd
- let's start vim:
```
vim learning_vim.txt
```
- How to exit:
  1. ESC ESC
  2. :q
  3. ENTER
- iii! I added a text (insert mode: ESC ESC i), but I just want to exit the vim without saving the content!
  1. ESC ESC
  2. :q!
  3. ENTER
- ok. Now I would like to add something to my file:
  1. vim learning_vim.txt
  2. ESC ESC
  3. i
  4. Please add sth, e.g., I love vim!
  5. ESC ESC
  6. :wq
  7. ENTER
  8. Let's see whether we saved the content:
```
cat learning_vim.txt
```
Survival 4 - emacs / nano:
```
nano
```
Notice, ^ means CTL/CONTROL.
If you look for sth like notebook: gedit p.txt

Remember

If the command does not print anything, it means it succeeded
Use: TAB TAB to get your commands autocompleted

Working with files

Let's go back to your home dir and create a dedicated directory for the exercises:
```
cd
mkdir workspace
cd workspace
```

Creating files with touch (to remember it) and writing to them with echo:

touch myfile.txt # create an empty file

echo "Ubuntu 18.04" > myfile.txt
echo "Ubuntu 20.04" >> myfile.txt

cat myfile.txt
echo "Mint" >> myfile.txt
echo "Debian" >> myfile.txt
echo "Redhat" >> myfile.txt
echo "Linux" >> myfile.txt

cat myfile.txt

Ofc, you can use the graphical editor or vim to change the file content:

atom myfile.txt

grep is a basic CLI tool for the automation. Notice it is case sensitive:

grep Linux myfile.txt

grep Ubuntu myfile.txt
# compare with:
grep ubuntu myfile.txt

grep -i ubuntu myfile.txt

A common use case, we have logs to analyze:

grep -i Error /var/log/*log
# alternative to `wc -l`
grep -c -i Error /var/log/*log

How to copy files, use cp:

cp myfile.txt myfile2.txt

ls

# we can `grep` all files
# that ends with `.txt`
grep Linux *.txt

How to move file (or rename file) from one directory to another?

mkdir mydirectory
mv myfile2.txt mydirectory
ls mydirectory
tree ../

# let's move the file back
# to the current directory `.`
$ mv mydirectory/myfile2 .

We also use mv to rename files, let's go back to our directories for Polish cities and villages:

cd ~
cd poland
ls
# sb asked us to use Polish word for cities
# - miasta
mv cities miasta
ls
tree ../poland

What if we need to have both, a directory with Polish name and English:
```
cp -r miasta cities
cd ..
tree poland
```
You should see miasta and cities.
Use rm to remove a file:
```
cd
cd workspace
rm myfile2.txt
```

... or to delete a directory with content:

cd
ls poland
rmdir poland/cities/warszawa

# does it work?
rmdir poland/cities

# if not, try this command:
rm -r poland/cities

To close this section, create in your home directory (*.txt are files):
```
biology/
|- trees
|      |- deciduous.txt
|      \- coniferous.txt
|
\- animals
    |- predators
    |   \- cats.txt
    \- herbivorous
        \- cows.txt
```
Tasks (use tree to check whether you completed the task):
1. Move files cats.txt and cows.txt under animals/,
2. Copy coniferous.txt to your home directory, check with ls ~ whether you succeeded,
3. Delete the animals directory,
4. Delete the biology directory.

Useful

We have in Linux hidden files. The hidden files starts with .:
```
cd
ls -a
ls -la
ls -la | grep bash
```
Environment variables, we use in every automation. Let's find out what the value is for the HOME and LANG variables:
```
printenv
printenv | grep HOME=
printenv | grep LANG=

echo $HOME
```

Printing environment variables:

# compare
$ echo "$HOME"
$ echo '$HOME'

# recommendation:
# always with { and }
$ echo "${HOME}"

Printing env variable to file:

cd ~
mkdir tmp
cd tmp

echo "$HOME" > home.txt
cat home.txt

Adapt your command line interface with $HOME/.bashrc
```
atom $HOME/.bashrc
```
Add at the end of the ~/.bashrc:
```
echo "Hi ${USER}!"
export MY_PHONE=9999
```
Open another terminal window or run bash in the exiting terminal window.
```
# notice TAB TAB works
echo $MY_PHONE
```
You can define a new env variable ad hoc in your terminal:
```
export SHOP_USER=natalia
echo "$SHOP_USER"
```

Create your first bash script my_script.sh with the following content:

#!/bin/bash

echo "Hi ${USER}! Nice to meet you!"
echo "Your home directory is ${HOME}"
echo "Your configured language is ${LANG}"

and run it:

bash my_script.sh

Where can I find X?

cd
find . -iname *.txt

# ensure we get the file:
find . -iname *.txt -type f

# find in the home directory `~`
# a directory `-type d`
# with name `poland`
find ~ -iname poland -type d

Working with text files

You got an export from your ecommerce shop koszyk1.txt:
```
milk,10,1zl
bread,1,4zl
```
Using cut:
```
cut -d',' -f1 koszyk1.txt
cat koszyk1.txt | cut -d',' -f1
```
extract:
```
1zl
4zl
```
Bonus task:
1. Print the user names from /etc/passwd
2. Extract month and days from /var/log/syslog
Another day, another weird export from an online shop koszyk2.txt:
```
product=mleko
price=1
product=chleb
price=4
```
With help of cut and paste, print on the screen:
```
mleko 1
chleb 4
```
Hint:
```
cat koszyk2.txt | paste - -
```
Let's learn how to replace strings, assuming we have koszyk3.txt with the following content:
```
product_category: mleczne
```
Our task is to replace mleczne (Polish word for the diary products) with the category ID M0:
```
product_category: M0
```
Hint:
```
sed 's/category/cat/g'
```
tr is very useful when you need to replace a single character:
```
cat koszyk3.txt | tr ':' '='
```
or remove it:
```
cat koszyk3.txt | tr -d ':'
```

Please find out what head, tail, and less do:

less /var/log/syslog
tail /var/log/syslog
head /var/log/syslog
head -n 10 /var/log/syslog

Given the following basket export structure (notice *.txt are files):
```
basket
|- chocolates
|   \- products.txt
|      wedel,2
|      goplana,3
|
|- dairy
    \- products.txt
       mlekovita,5
       zimnemleko,4
```
1. With one command print the price for each of the item:
```
2
3
5
4
```
2. With one command (find it with help of Google on stackoverflow), calculate the basket value:
```
14
```
Notice how easy is to find a solution for a common problem in bash.

Homework

Install one from these two:

ohmybash / bash-it if you are on Linux
ohmyzsh if you are on Macos (a blog post for MacOS) or you are on Linux (blog post)

There are many plugins that gives you super powers in your terminal, you can check the top plugins on this page.

Additinal materials

better bash scripting in 15 minutes

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

README.md

README.md

Linux basics

Survival

Remember

Working with files

Useful

Where can I find X?

Working with text files

Homework

Additinal materials

Files

README.md

Latest commit

History

README.md

File metadata and controls

Linux basics

Survival

Remember

Working with files

Useful

Where can I find X?

Working with text files

Homework

Additinal materials