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In this lecture I want to talk about environment variables.

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Environment variable is simply variable that is available during the entire session in the shell.

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And you could use environment variables, for example, in shell scripts.

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Also, environment variables like path are used by system itself.

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If you want to get a list of all environment variables that were set, you could simply type command

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env three letters and you'll see a set of key value pairs.

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Here.

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On the left you see name of the variable like term user terminal version and so on.

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And after equal sign you see value for a specific variable.

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For example, here you see variable name like terminal and its value is iterm2.

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Here if you scroll a bit up, you'll see variable called LS colors and its value is set here.

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Also here you see such variable as WD and it is set to slash root.

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You see such variable as shell and it is set to bin bash.

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Now I'm logged in via SSH to Docker container as root user.

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Let's now try to open up new SSH session as Bogdan User recap that I have created a new user before

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and if you have not done it, please create a new user with any username.

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And here let's use again SSH command.

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I'll use same port 2222.

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It is exposed port for docker container and here will be username Bogdan at localhost.

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Like this.

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Let's enter password for Bogdan it is 123 in my case and I'm in.

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Let's now enter in the command here and now I'll see a set of similar env variables.

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Let's quickly go back to this tab where I have entered the same command for root user and let's compare

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those outputs.

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Here is output for root user and for example here you see environment variable user that is equal to

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root.

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But if I switch to this tab, I'll see that user is set to Bogdan And also here you see different SSH

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connection variable.

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Here in this case, you see port three, five, five, nine, eight.

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And here in this case, you see another port, three, five, five, seven, eight.

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Because here are two different sessions and actually same information you see here on this line as a

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client.

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If I go back to another tab where I have logged in directly to the container this tab and enter in the

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variable, I will not see such variables as I see here as a client and as a connection.

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And that proves that set of environment variables is created when specific user logs into the system.

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And depending on the conditions, logging conditions, those sets will be different.

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All right.

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That is a set of environment variables.

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Now, question how we could access any variable.

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It is very simple.

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We have done that before.

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Let's clear terminal here and simply enter echo dollar sign path, for example.

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And here I get value for path variable.

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And now let's try to get other variable, let's say user dollar sign user, and I get value for another

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variable user.

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It is very simple and of course you could use variables in shell scripts, for example, in order to

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access some values.

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And also you could set additional variables if you want.

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For that you need to use command export and after export will be name of new variable or existing variable.

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And next comes equal sign and value for the variable.

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For example, let's create new variable called my underscore new variable like this.

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And let's set it equal to simply test like this.

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Let's press enter.

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And now let's list all variables.

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And actually, if you want, you could use here grep and here will be my let's say new like this and

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I'll get value for my new variable.

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It is actually available also in this output.

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Let me scroll a bit up and yes, here is this variable.

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My new variable and its value is test.

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And of course now you could easily access this new variable.

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Let me clear terminal echo dollar sign my new variable and here is its value.

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That is that simple.

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Also, when you run some applications like for example, Node.js, Python, Java applications, many

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applications require runtime variables and usually you could set such environment variables before start

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of any application using similar approach.

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All right, that's all about environment variables.

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And now you'll get small challenge.

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You need to create a new variable called my name my underscore name.

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Afterwards, you need to create a new shell script called name Dot as H.

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And inside of this new script you need to print your name to the terminal using Echo command.

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And afterwards, of course, you need to execute this script.

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Wish you good luck guys.

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And after the post I'll show you a solution for this challenge.

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I'll see you next.

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Bye.