Here we have Bash AND and OR operators. If we take a look at here, really, the key idea here is that when you have this double ampersand, it prefers to AND. You'll see this a lot when you're using both the Docker file format and also you'll see this with Makefiles. What's nice about this is that you'll be able to chain things together. Really, that's the idea, when you have this double ampersand, is you want to run multiple commands, but only if the first command worked. Likewise, there's also the OR operator where if this is the first condition false, then the second condition will run, maybe echo "Hi." But if this first condition was true, it actually won't run the second condition. So it really, it's one of them. It's either or essentially when you have this OR operator. We'll take a look at both of these in action. They really come in handy when you're using the Docker file format and the Makefile format, which are essential tools for someone that is mastering Bash. Let's take a look at Docker Hub. This is a great place to learn about Bash AND/OR conditions and I'm at the Python official image. If I scroll down here and I just take the first tag I see, we can see this is a complete Docker file. We'll see many examples of the AND operator here. Notice this, we have a slash and we have an AND, AND, AND, AND, AND. Basically, what's happening under this run statement is none of this will continue to work unless the command before it was successful. This is a great way to learn how to use these commands together and potentially get some ideas for other things. But you'll see here, this is a critical component of it, is that every subsequent command must work for the full thing to work, which again makes quite a bit of sense. You see how they do this style here, where they do a slash and then they do the AND, AND, and then they run the next command. Similarly, if we go to this repo here called Bash AND/OR, I've got a Codespace setup and we have a shebang line here. Notice I did something similar. In fact, if we wanted to copy that style here, we could do that. Looks like that's the cool thing to do. We could go here and then put this right in front. We can just say double ampersand, and then the same thing, we can just move this down. This would look a little bit more like the new style that people are doing when they're building out multiple lines inside of a Docker file. We'll do this as well. We'll do another. Then again, we can just put this one like this. If I look at this, what's going to happen is it will first create the first file, then it'll create the second file, and then it'll create the third file. Then it'll go through here and do a ls command that counts the amount of files created and prints it out. If we go through here and we run this, we can say, and.sh 3, right? Look, those three files were actually created. This is a very clever way to use this AND operator, especially when you're doing a sequence of commands. Now let's see how it would fail. This is a really good example of how it would fail. Notice that this file doesn't exist, right? We don't see it in our directory here. In fact, I'll even just do a remove command to get rid of all the text files. But notice if I run this, what will happen is that the second part, it worked, won't actually print out. The reason why it doesn't print out is because this is a command that doesn't work. This is an error condition. The ampersand, the double ampersand won't work, right? That's really the point of using the double ampersand. Likewise, if I do this, this also won't print this out. But if I do true, which is an operator that I can use, we can see that, yes, it does work. So now that we know how the AND works, let's go ahead and go to the OR. If we go over here, we can see that in this case, the opposite thing happens. If I run False, it basically runs the other one instead. But if I run something where the first statement is true, this second part won't run because this was able to be successful. So if I say, run this, but not that, there we go, run this but not that, this one did not actually run. They're both great operators to use, and a great way to learn them is by looking through Docker Hub, and really, once you get the hang of it, you'll be able to build your own Docker files in no time.
