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Hello, the beautiful people.

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So in the last few videos you've been learning how to create and modify files and directories in all

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kinds of different ways.

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And when you're working with files in your computer, it's really easy to misplace one or two and wonder

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where an important file that's new to you such a configuration file might be hiding.

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So in this video, I'm going to show you how you can use the locate command to actually search for files

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by name and find them no matter where they might be hiding on your computer or with the command line.

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Pretty cool.

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Right?

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So we're going to break this up into two parts in this video.

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You're going to learn how to use the locate command and some of its options.

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And you're also going to appreciate some of the limitations that the locate command can have.

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And then in the next video, the one after this one, you're going to learn how to overcome those limitations

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and also how to access administrator privileges on the system in order to update a database.

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So this is all going to be very cool stuff, very, very exciting.

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It's going to give you super powers, basically.

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So let's just go ahead and get right into it.

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Okay.

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So the locate command is actually really simple to use, but it's very, very useful.

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Now, the first thing that you need to know about the locate command is that it works by searching a

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database file that's on your system.

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Now this database holds location information about every file that's on your system.

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And the way that the locate command works is that you will give it some pattern to look for and then

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locate will search the database for every path that matches that pattern and give it back to you on

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standard output.

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Now this is actually really easy, so let's just jump right in and get a feel for how this works.

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Okay.

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So for example, let's try and find every file in our system that ends in dot conf.

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Okay.

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Now dot conf is a file extension that is common on Linux to indicate that this file is an editable configuration

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file.

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And because file extensions don't really matter to Linux, Linux users and developers usually leave

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meaningful file extensions like dot com so that you can understand what the file might be about just

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from reading the file extension.

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Dot log is another common example and it's used for log files that store error messages from programs

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and server applications.

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So you can look at these log files later on in case anything breaks and see where stuff went wrong.

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But we're going to look at files that end in dot conf now to search for all the dot com files on our

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system.

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All we need to do is type the locate command and then give it the pattern we want to search for.

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Now you should start remembering what we did about regular expressions and wild cards.

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So just think for a minute.

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How would you make a pattern that matched any file that ended in dotcom?

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Just think about it for a second.

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And you might remember that perhaps you need to have the star wildcard and then com.

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This says anything that matches this pattern here and so that means it can start with anything and then

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end in dotcom.

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So this pattern will check for files that end in dot conf and that's actually all we need to do.

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Right.

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So if we do that and press enter.

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Whoa.

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Right.

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You'll see, like a whole bunch of different file paths come out, but you'll see that every single

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one of these files ends in dotcom.

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Now, it's worth noting that by default, Linux is case sensitive, but you can make searches using

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the locate command case insensitive by giving the locate command the AI option.

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So, for example, if we just clear the screen and we do locate and just say dot com, but spell everything

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in uppercase, now you'll see that we actually get no results because Linux searched case sensitively.

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It had to be exactly everything in uppercase but to make locate search in a case insensitive way, we

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could give the locate command the AI option.

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And what this does is say, hey, don't worry about the case.

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I'm just looking for these letters.

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And when I do that we get again files that end in dot conf.

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So that's something to bear in mind there.

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And you can also limit the amount of results that you get.

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So we get hundreds of results coming out of this one.

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Look how many.

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There are a lot of configuration files, but if we clear the screen, we could say, okay, let's search

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in a case insensitive way, but let's limit it, limit the output to just three results.

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Okay.

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And you can see here that I am using the long form limit option.

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So we've got the two dashes, then the word limit, and then we give it its command line argument,

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which is three.

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So this limit option has an input of three.

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So when I do that, you can see that we are just limiting it to three results.

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If I change that to five, we'll get five results for change that to ten, we will get ten results and

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so on and so on.

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So this is useful to if you just want to get the first few results or you only want to find a few results,

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you can limit it like that as well.

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Now the key consideration to have when using the locate command is to understand that it uses a database.

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In fact, you can actually find out information about the database using the capital s option.

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So if I click the screen and we use locate and give it the capital s the upper case option, I can press

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enter and you'll see that we get some information about the database itself.

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So it tells us the path to the database file as well as some size about the general, some information

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about the general size and complexity of the database.

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So I'm actually going to save this information using a redirect.

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So if I use locate s and I'm going to save that into something on our desktop, let's call it database

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before txt.

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So well we've got a file called database before that txt on our desktop with all that information saved

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in it.

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So you can see redirection is actually a very useful skill and you'll just use it all the time and you

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should be proud.

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Now you understand how to use it as if it's nothing, right?

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So this database, just like any of the database, is only useful if the information in it is up to

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date.

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Okay.

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Now the database by default is updated just once a day.

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So this means that anything that happens in the meantime is not logged in.

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The database files could have been created, moved, deleted, and unless the database is updated,

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then the locate command will start to give incorrect results.

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Now there are a few options that come with the locate command to help minimize this issue.

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They can't make the database list files that haven't been added to it yet because that's impossible.

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But they can prevent the locate command from showing files that have been deleted in the meantime or

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links that no longer work.

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For example, there is the option that requires the locate command to check that the file is existing

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before it reports it back.

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So for example, if we did locate with the e option of everything that ends in conf, then this would

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check the database for all files that ended in dotcom, but also do a check to make sure that those

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files actually existed before reporting them rather than just taking it from the database directly.

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It will take them from the database, but also do a check to make sure that they are there.

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So it gives you that extra bit of assurance.

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There is a long form option for the options.

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So instead of typing dash E, you could type double dash existing and that does exactly the same thing.

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So that's very, very useful stuff.

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And sometimes there are shortcuts and links on your system called symbolic links that might be broken

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if files get moved around now to check whether these shortcuts and links are still valid before the

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locate command reports them back.

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You can use the capital L or the follow option like this.

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So locate follow everything that ends in dot com for this.

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So if there are any symbolic links or if there are any links to files, it will check that they aren't

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just dangling.

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They actually arrive somewhere, arrive to the right place.

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Before reporting it back.

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So that's another bit of assurance.

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And of course you can do both at the same time.

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So existing and follow gives you basically the maximum assurance you can get there.

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And again, you can combine it with case in sensitivity and limit it to just show five.

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And you can combine all these options showing you here just how powerful the Linux command line can

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be to have multiple different functions going at the same time.

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Now, these safety features are all well and good, but what we really need to solve our problem is

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to have a way to update the database whenever we like.

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And there is it's called the update DB command.

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And for the purposes of time, we're going to cut the video here and pick up learning how to update

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the database in the next video.

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So I'll see you there.