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[Intro Music]

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In this lecture I want to talk

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about environment variables.

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Environment variable is simply a

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variable that is available during

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the entire session in the shell.

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And you could use environment

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variables for example, in shell

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scripts. Also environment variables

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like PATH are used by system

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itself. If you want to get a list

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of all environment variables that

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were set, you could simply type

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command 'env'; three letters; and

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you'll see a set of key-value

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pairs. Here on the left you see the

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name of the variable like TERM,

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USER, LC_TERMINAL_VERSION, and so

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on. And after equal sign, you see

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value for a specific variable. For

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example, here you see variable

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name, LC_TERMINAL; and its value is

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'iTerm2'. Here if you scroll a bit

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up, you'll see a variable called

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LS_COLORS, and its value is set

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here. Also, here you see such

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variable as PWD, and it is set to

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'/root'. You'll see such

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variable as SHELL, and it is set to

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'/bin/bash'. Now I'm logged in via SSH to

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Docker container as root user.

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Let's now try to open up a new SSH

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session as 'bogdan' user. Recap

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that I have created a new user

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before. And if you haven't done

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that, please create a new user with

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any username. And here let's use

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again SSH command, I'll use the

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same port 2222. It is exposed port

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for Docker container. And here will

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be username 'bogdan@localhost',

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like this. Let's enter password for

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'bogdan' it is '123', in my case; and

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I'm in. Let's noe enter 'env'

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command here; and now I'll see a

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set of similar 'env' variables. Let's

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quickly go back to this step where

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I have entered same command for

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'root' user; and let's compare those

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outputs. Here was output for

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'root' user; and for example, here you

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see environment variable USER, that

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is equal to 'root'. But if I switch

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to this step, I will see that USER

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is set to 'bogdan'. And also here

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you see different SSH_CONNECTION

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variable. Here, in this case, you

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see port 35598. And here in this

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case, you see another port, 35578.

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Because here are two different SSH

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sessions. And actually same

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information you see here on this

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line, SSH_CLIENT. If I go back to

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another tab, where I have logged in

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directly to the container, this

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step, and enter 'env' variable, I

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will not see such variables as I see

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here, SSH_CLIENT and SSH_

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CONNECTION; and that proves that

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set of environment variables is

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created when a specific user logs

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into the system. And depending on

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the conditions, login conditions,

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those sets will be different.

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Alright, that is a set of

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environment variables. Now question,

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how we could access any variable?

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It is very simple. We have done

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that before. Let's clear terminal

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here and simply enter 'echo $PATH',

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for example; and here I

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get value for PATH variable.

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And now let's try to get other

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variable, let's say USER, '$USER';

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and I get value for

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another variable, USER. It is very

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simple. And of course, you could

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use variables in shell scripts, for

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example, in order to access some

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values. And also you could set

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additional variables if you want.

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For that you need to use command

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'export'; and after 'export' will be

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name of the new variable or

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existing variable; and next comes

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equal sign; and value for the

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variable. For example, let's create

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a new variable called

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MY_NEW_VARIABLE, like this; and let's

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set it equal to simply 'Test', like

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this. Let's press Enter. And now

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let's list all the variables. And

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actually if you want, you could use

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here, 'grep', and here will be 'MY_',

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let's say 'NE', like this; and I'll

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get value for MY_NEW_VARIABLE. It

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is actually available also in this

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output. Let me scroll a bit up and

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yes, here is this variable,

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MY_NEW_VARIABLE, and its value is 'Test'. And

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of course now you could easily

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access this new variable, let

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me clear terminal, 'echo $

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MY_NEW_VARIABLE'; and here's its

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value. That is that simple. Also,

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when you run some applications,

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like for example, Node.js

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Python, Java applications, many

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applications require runtime

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variables. And usually you could

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set such environment variables

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before start of any application

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using similar approach. Alright,

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that's all about environment

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variables, and now you'll get small challenge.

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[Background Music]

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You need to create a new

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variable called MY_NAME,

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MY_NAME. Afterwards, you

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need to create a new shell script

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called name.sh. And inside of this

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new script, you need to print your

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name to the terminal using 'echo'

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command. And afterwards, of course,

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you need to execute this script. I

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wish you good luck guys, and after

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the pause, I'll show you solution

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for this challenge. I'll see you next. Bye.

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[no audio]