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Hello everyone. Now that you have learned how to

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assign permissions to file and directories using

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letters, but now do you know you could also assign

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permissions using numerical values? Yes, so every

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time you have a file, you could assign permission

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to that file or directory using numerical digits.

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And how does it work? So, you know, chmod ugo,

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is for user, group, and other, plus r to a FILE

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would actually assign a read permission to

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everyone. If you want to use in a numerical way,

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you could do chmod 444, and the FILE, which

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will assign exactly the same permission, as in the

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first command. And the end result will be read,

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read, and read permission only to everyone for a

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file. Now, how does that 444 changes and assign

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that permission? Let's look at it by looking at

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the structure of a file. So as you all know,

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owners assign permissions on every file and

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directory, and we have users, and they have three

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type of permission read, write, executable. Group has

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three type of permissions, and everyone else or

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others or all have those three type of permissions

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as well, so we all know that. Then let's go more

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specifically that the first three bits that we have

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already covered are for users, the owner of the

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file, the secondary bits are for the group, and

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the last three bits are for the others. Now,

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moving on, the table below that I'm going to show

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you are is actually, assigns numbers or permissions

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to the permission types. So let's look at that

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table. This is the table is something that you

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need to remember. Now, if you have zero assigned,

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that means no permission, a one is for executable,

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two is for write, three is for execute plus write,

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four is to read, five is to read and execute, six

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is to read and write, and seven is to read or write

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and execute. Now how does these all seven

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numbers, all eight numbers work. If I have, if

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I do chmod 764 to our file, then it means the

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first digit will always be for the user itself. So

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seven meanings, if you look at the table, it means

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this is going to assign read, write, and executable

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permission to the owner of the file. The second

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letter, which is in this case is six, it means

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that a read and write only and that will be

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assigned to the group. And the last one is for

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that is for others, and the four means only read,

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so only read will be assigned to the file. So

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again, first digit is for users, second digit is

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for group and third digit is for others. So let's

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try in our Linux machine, in our lab machine, and

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see how it works. So I'm going to create a file,

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let's say, sam, and we're going to touch and

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create a file sam. I will do ls -ltr.

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and the file is there. By the way, I am logged

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in as myself, and I am in my home directory. So

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let's clear the screen by typing clear, and do ls

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-ltr again, and you will see the sam file is

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all the way at the bottom. Now by

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default, I have given the permission as read, write,

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read, write, and just read. If you want to change

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this permission to 764, meaning me as myself would

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have read, write, and executable. And group will have

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only read, write. And everyone else will just have

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read, then all I have to do is chmod 764 sam.

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Now when you do ls -ltr, you

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will see right at the bottom, I have now read, write,

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executable, read, write for the group, and just read

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for everyone else. Now if I wanted to remove those

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permissions, let's clear the screen and just do ls

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-ltr only on sam file so just only that

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file shows up on the list. If I wanted to remove

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every permission of everyone else,

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I will do chmod 000 sam, do ls -ltr by

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hitting up arrow key, which will bring the last

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ran command, and you hit enter. You will see all

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the permissions are gone. Now, if I wanted to,

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let's say if I want to assign, read and write

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permission only to myself, then how are you going

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to do it. Then all you have to do is chmod,

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myself would be the first letter, remember, the

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first, sorry, the first digit. So I just want read

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and write only, so that would go for number six.

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Because if you look at the table, number six only

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gives read and write. Then the rest, I don't want

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to assign anything else. So you cannot leave

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anything empty like that, so you have to leave 00.

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So no permission at all, type it, sam. Now if you

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do ls -ltr on sam, you'll see I only have

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read and write. So let's try one more time. What

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if I want to keep the permission read and write

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and I wanted to assign read permission to the existing

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permission for others? Meaning, right here, the

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last three bits I want r here. So for that, I

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would do first of all chmod, and of course, I

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want to keep the permission and that permission is

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six. For group, I don't want to assign anything.

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And for others, I want only read. And if you look

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at the table, the read, number associated with read

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is four. So if I do hit four, and type sam, and

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now if I do ls -ltr on sam, and you will see

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read and write, and read is only given to others in

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this case. Let's look at one more, and last one

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example, what if I want to assign executable

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permission to everyone in the system. So

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you do chmod, now what's the executable? The

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executable permission, if you look at it, it's

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number one from the table. So that means 111.

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Because I want to assign executable to myself, to

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groups, and to others, so 111 and sam file, done,

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let's do ls -ltr, and you will see it's

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only given xxx, so now you can only get executable. If

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you want it to have executable and read, then you

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would have given number five, and 111, which will give you

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[No audio]

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yourself executable and read, and the rest

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only executable. Anyway, that's how you use this

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table. Or that's how you use the numerical letters

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or sorry in numerical digits to assign permissions.

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Also, if you do not remember this, this chart, or

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if it's not handy with you, you can also go online

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there are many calculators online that you could

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use you. All you have to do is type online

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chmod calculator and it will come up. A lot

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of websites have those free calculators for you,

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all you have to do is click on the ownership or

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group or public meaning others whatever that you

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want to do, check those marks and at the bottom,

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you will see Linux permission, it will give you

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the exact number that you need to type it in for

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chmod, it's very easy. Anyway you could do,

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either way you could do using the

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letters or you could do using the digits. I just

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want to cover both methods so you understand how

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the permission works using both methods.

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[No audio]