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In last section we found that we were able to connect to read a C lie inside of our running docker container

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and notice how mine is still running over here on the second window.

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By adding on the dash I t flag.

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So when I did that we saw.

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Yep we got this prompt here.

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We could enter stuff in.

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I could then first control C to exit back out.

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However if I tried running this command without the I.T. flag it appeared that I just got kicked directly

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back over to my terminal.

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So in this section I want to give you a better idea of what this dash I.T. flag right here is really

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doing for us.

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The first thing you need to understand is a little bit more about how processes run inside of a Linux

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environment.

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As a quick reminder when you are running Docker on your machine every single container that you are

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running is running inside of a virtual machine running Linux.

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So these processes are really being executed inside of a Linux world.

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Even if you're on Mac or Windows.

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All right so that mind in this diagram we've got three different running processes all inside in theory

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of a running container or really inside of a Linux environment.

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Every process that we create in a Linux environment has three communication channels attached to it

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that we refer to as standard in standard out and standard air these channels are used to communicate

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information either in to the process or out of the process.

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Standard in as you might guess is used to communicate information into the process.

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So when you are at your terminal and you type stuff in the stuff you type is being directed into a running

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standard and channel attached to say the red a apply the standard out channel that is attached to any

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given process is going to convey information that is coming from the process.

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So standard out might be redirected over to your running terminal and that's going to end up as being

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stuff that is going to show up on the screen standard error is very similar but it conveys information

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out of the process.

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That is kind of like an error in nature.

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So if red Seelye has some error inside of it that's can be communicated to the outside world over the

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standard error channel and very similar to standard out.

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That's going to be redirected to show up on the screen of your terminal.

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So how does that relate to the I.T. flag.

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When we do the docker Zac dash I.T. will the I.T. right here is actually two separate little flags.

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In reality it's a dash eye and a dash t like so.

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But by convention we usually just kind of shorten it down to be simply I.T. which is 100 percent equivalent

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to the two separate flags the Dash I on here means when we execute this new command inside the container

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we want to attach our terminal to the standard in channel of that new running process.

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So by adding on the dash IV flag we are saying make sure that any stuff that I type gets directed to

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standard in of red a CLIA the dash t flag is what kind of makes all this text show up a little bit pretty.

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Now in reality it's doing a little bit more than that but at the end of the day the real effect that

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the dashed you flag is to make sure that all the text that you are entering in and that is coming out

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shows up in a nicely formatted manner on your screen.

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And again it's doing a little bit more behind the scenes in that but at the end the day that's kind

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of its effect let's try attaching or doing our Docker Zach on the running container one more time and

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leaving off the dash t flag and just seeing what happens so I'll do a docker P.S. to get my containers

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idea again and I'll do a docker exec and then we'll do only Dash I this time I'll put the idea in and

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then I'll do red as CSI.

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And so now this time you'll notice how I have my cursor over here.

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It appears that this thing is waiting for input but I didn't do not see that kind of nicely formatted

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indentation I saw before and if I put in like set my value five before I had a little bit of auto complete

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functionality but this time that auto complete is definitely not there.

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I can still run that command though and I still see okay and I can still do get my value and I still

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see the value come out.

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But again all this all this stuff is not nicely formatted and so that's kind of the purpose.

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More or less kind of simplifying things here just a little bit of that dash t flag okay.

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That's pretty much it.

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That's the purpose of I.T. it allows us to have stuff that we type into our terminal directed into that

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running process and allows us to get information out back over to our terminal.

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So then mind let's take a quick break right here and continue in the next section.