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[Intro music]

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Command syntax. Every time you run a command, you

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have the option, and you have argument. Command

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typically have the syntax like command, like as if

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you are running command, let's say ls, it's a

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listing command, the option is going to be the

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-l or ltr, whatever we use in argument if

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you are looking for a specific file. Now, what are

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the options again? It modifies the way that a

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command works. It usually consist of a hyphen or a

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dash, followed by a single letter. Sometimes some

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commands accept multiple options, which can

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usually be grouped together for a single hyphen.

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And what are the arguments? Most commands are used

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together with one or more arguments. Some commands

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assume a default argument if none is supplied, and

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arguments are optional for some commands and

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required by others. Let's look at our Linux

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machine and I will explain you exactly how the

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command syntax works.

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[No audio]

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So we are in this Linux

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machine. Again, the first thing you always have to

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do is find out who are you or which user

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are you logged in as. So you do whoami, you are

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yourself. Second thing, which directory you are in?

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you are in slash home and slash your user. This is

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your home directory. And by the way, every time

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you start to type cd, no matter which directory you

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are in, you're always going to come back to your

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home directory. Now when I mean by command, so the

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first, when we run command ls in your directory,

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you will see all the directories and files it has,

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without other details that you get. So when you

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use the option, so you do ls -l, this will

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list everything that you have in your home

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directory. And then it will also give you all the

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details whether it's a directory,

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file, size, who owns it, and all the bunch of

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stuff. So you adding the option with the

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-l. So options can also be grouped. When

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I'm meant the group, it means ls -l, and you

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could add another option to it, which is t. So you

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see, it will let list all the contents of your

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directory by the time they were created. Then when

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you do another option with that ls -ltr, it

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will still give you the all the listing, but it

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will list all the newest files or directories

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starting at the bottom and the oldest one from the

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top. So that covers our ls as a command. And then

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the second one is the option which we use ls -ltr.

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And what do we mean by argument? Let's look

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at the argument again.

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[No audio]

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Argument can be used to be

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more specific, meaning let's say if you wanted to

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know just a file, bart, so you do ls -l bart.

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This is going to only list the file bart. If

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you want to know the details about the file bart,

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who owns it, was a permission on it, you could just

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use that argument to list this. Now you have

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command, you have option, and you have argument. If

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you wanted to, let's say delete a directory, which

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is by the way the command to delete is rm, remove, -f,

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which is to remove without asking you

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whether they should delete it or not, so you could

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just do rm -f.

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And then let's say I want to remove seinfeld. And

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when you hit Enter, it's gonna say cannot remove

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seinfeld, Is a directory. So we have to use an

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option to remove it and to remove a directory

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with an option, it is, so let's say if this time we

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will take out f, and we just do r. So r is an option

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to remove a directory, so when you hit enter, it

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will remove the seinfeld. And how do you validate

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that? You do ls -ltr, and you're going to

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see in your listing seinfeld directory is gone.

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And I want you to recreate it again, it's mkdir

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[No author]

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seinfeld, you do ls -ltr, and there you go.

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This has at the bottom, it has your new directory

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seinfeld. So again, to wrap up this lesson, we

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covered the command, the option, and argument. And

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the best way to find out which options you have

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available with the command you always run man,

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which is stands for manual, and ls, which is the

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command. When you hit enter, it will give you a

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user command, a manual, which will give you all the

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options like if you run -a, it will ignore

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entry starting with dot, if you uppercase, A, B,

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and C, and so on, and you could just hit space to

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go down and see other option. Keep hitting space,

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keep hitting space, keep hitting space, and you'll

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see all the different options, and by the time you

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get to the bottom and you cannot hit the base

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anymore, you could just hit Q to get your prompt

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back. You could also run a man ls, hit enter. And

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if you just want to view the first page without

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going any further, you could just simply quit out

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of it right away instead of just hitting space,

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space and go to the end, so you hit Q. So this is

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what primarily we covered in this lesson. Again,

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command, option, and argument.

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[No audio]