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Wildcards. What are wildcards? Just as the name

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says they are wildcards, meaning if you play cards,

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and you know in Poker, or Blackjack,

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they do pick a card, like 10 or 9, whatever the

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card and you could match it to any of the cards to

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make your flash, trail, or whatever that you like.

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So that is kind of a wildcard. So just like that,

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in Linux, we use wildcards to get the output that

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we are looking for. A wildcard is a character, now

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this is a definition right from the Linux

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dictionary, that can be used as a substitute from

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any of a class of characters in a search. So there

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are many wildcards, but the most basic ones I have

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listed here, there are three. The first one is the

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one I use most of the time is asterisk, which is

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also referred to as a star. A star represents

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zero or more characters, anything that matches

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that star placeholder. We'll look into that in a

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moment when we actually use the star wildcard in

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our Linux machine. Then we have a question mark,

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represents a single character. So if you have a

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file name, text, and you are looking for any files

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that has the word text, and you could use T E,

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instead of x, you could just put question mark in

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there, and then t, that means what ever falls that

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had T E doesn't matter what's inside of the x and

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the last letter is x, the t, that didn't work. The

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third one we have brackets, which represents a

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range of characters. So it's better we look at

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done Linux machine to understand them more deeply.

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I'm going to bring up my machine real quick.

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Where'd it go? Right here. I'm logged in always as

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myself. And I'm in my home directory, of course.

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Now, right now, these are the files and

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directories in exist in my home directory, I want

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to create nine files that has a name, let's say

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abcd, one, and xyz. And then same thing instead of

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one, it just increments the number 23456. I could

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do this touch abcd1-xyz, one

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time, then hit up arrow key again, change one to

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two, change two to three, and keep going. But don't

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you think it's cumbersome and tedious? It is right.

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So we use wildcard to perform that task because

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you're going to create nine files. So it's just a

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practice that we are doing for nine files. Trust

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me, in corporate environment, you probably going

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to have to create like 1000s of files, what you're

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going to do, you're going to just hit up arrow key

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and type it 1000 times. No, that's not

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productive. So then what do you do? We use

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wildcards. So first of all, I'm going to do is I'm

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going to remove these files one by one. Again, I

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can remove it wildcard, as well. But let's create

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it first and I'll show you how I can remove it. So

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I have two left. Now I could use a wildcard to

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remove both in one shot, remove abc wildcard. So

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what is telling it, remove everything that has a

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file name that starts with abc and whatever that

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comes afterwards, you don't care, just remove it.

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I hit enter, ls -ltr, and you'll see all

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those two files are gone. Now I'm going to create

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nine files. And to create nine files, I'll use the

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command touch. As you know the touch is a command

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to use, and then there's a wildcard another

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wildcard that's called curly braces. So I was

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creating file abcd curly braces 1 dot dot 9,

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because I'm going to create nine files. So this

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curly braces 1 dot dot 9 starting to create nine

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files that has the digit one through nine and dash

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xyz. When I run this command, what do you think

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that I will have listed in my home directory? I

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will have nine files right here at the bottom, you

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will see I have nine files. Awesome, right? This

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is what you wanted to do.

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It is much more faster to do in the wildcard as

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opposed to typing one by one. So let's use

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the asterisk, I just want to list every

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file name that starts with abc. You do abc

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asterisk, and you will have all the files that

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starts with abc. I want to remove every file that

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starts with abc. You could remove one by one, abcd1

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and so on, and so forth, again, very

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cumbersome, don't do it. You're a system

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administrator, you are smart, folks, you don't

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want to use the commands one by one, what do you

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would use, you'll use a wildcard. So you will do

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abcd, or ab, and do asterisk. The reason I

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picked the four letters, because if I just pick a

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and hit asterisk, it will also remove any other

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files in my home directory that starts with a and

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which I don't want it to do it. Right now, I don't

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have any files. So let's say if I create a file

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touch a. So now I have all the files and a. So I

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just want to confirm I don't have a so I don't

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delete any file accidentally. So yes, I don't have

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any file that begins with a other than these. So

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if I just do remove a asterisk, it will remove all

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the files that starts with a. Let's check it.

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See, all those files are gone. Isn't that cool?

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Yes, it is. I love this asterisk because I use it

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all the time. I'm going to recreate those files

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again, by hitting up arrow key that will return my

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last ran command. Just confirm they are there. Now

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what if I want to remove everything that ends with

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xyz, same way remove, but this time we'll put

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asterisk in front of xyz, hit enter, boom, all

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gone. Also, I'm going to recreate it just for the

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exercise of this lesson. It created nine files.

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Now we'll move on to the next wildcard which is

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the question mark. The next question mark is

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telling it ls -l ?bcd*.

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Okay, what am I asking here, I'm asking is

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give me all the files that has whatever the

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character is the first, as long as the other

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characters has bcd, and whatever comes

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afterwards. These are the matching files because

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whatever the first character is, whether it's a or

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not, I don't care. I just want to make sure I will

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get the listing of the files that has bcd in it

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after the a. So that's how you use question mark.

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And the last one we have brackets. Bracket is going

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to tell me that give me anything that has c or d

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letter in a file. It's just that simple. Either c

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or the d, either f or this and that. So you put

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all that stuff that you're looking for inside of

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the bracket. And you will have all those files you

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see here. And it went so fast. So I'm going to put

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it in more output, I want to see one page at a

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time. And you'll see it gave me and it has a, it

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has b, every file that I'm getting as either has a

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or b either has a or b. So that's how it works.

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That's how wildcard works. Again, now I want to

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get rid of all the files that has x and y in it.

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Awesome, I have my wildcard I'm not going to go

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and delete one by one. So this command is telling

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the show that go ahead and please delete all the

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files that has x and y in it. And x and y has to

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be together of course. So if we do have these

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matching files xy and it will go ahead and delete

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it. And all of them are gone. So wildcard not

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necessarily is used just with ls or remove. You

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could use it with any of the commands we have. You

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could use it with all the commands we have learned

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so far. Try it. Try it with different commands. If

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it doesn't work, that's okay. Go online, google it

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and try wildcard, wildcard examples. Try them,

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just get familiar with them. This will help you a

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lot in your job, I promise you.

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