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We have just discussed what is the difference between absolute path and relative path in Linux?

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And you know, that Slash is simply a root directory in Linux computer.

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Also, you know that when a user logs into Linux shell either locally or remotely, he or she logs basically

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into home directory and by default you will see this tilde sign in command prompt and if you enter w

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you could find location of your home directory and location of home directory for this root user is

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simply slash root.

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It is absolute path.

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All right, now let me go to root directory by typing CD and slash and you see that the command prompt

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was changed and let me use here command ls that will list all directories and files inside of the root

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folder.

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Let's press enter and here you'll see some directories and files.

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And please notice that those names have different colors and if for some name doesn't have any color,

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it means that it is a regular file like hello dot txt.

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I have created this file in one of the previous lectures.

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Same relates to this file and this file directories are colored in blue color like proc run, serve

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and cis and in light blue color like Lipa or sbin Linux colors Linux.

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And there are two types of Linux soft links and hard Linux.

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I'll explain what is link a bit later.

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If you want to see the details about every directory or file, you could add additional option ls l.

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And with this option you'll see actually a table that contains a bunch of additional information in

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this table.

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First, you see permissions.

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Here is permission, here is permission and so on.

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Next you see quantity of links to specific directory or file.

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Next comes username, next group name afterwards size in bytes.

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For example, here you see size.

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That is 4096 bytes around four kilobytes.

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Next date when directory of file was created or modified.

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And finally, name and colours in this output are the same as you see when you don't use this option.

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And please notice that for Linux that are colored using light blue color like this one or this one,

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you'll see actual link and it means that for example lib 64 simply points to another directory user

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lib 64 and the lib points to user slash lib.

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All right, let me now explain you in details what those permissions here mean.

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First, let's have a look at first character d l or dash if it is a file like hello dot txt or std r

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dot txt then first character will be simply dash.

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Here you see dash here you see dash and here you see also same sign.

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Next for directories.

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First character will be d like in this example home directory or in this example media directory and

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so on.

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And Linux will start with L character like in this example, this one or this one.

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Next, you see permissions for a specific file or directory, and they are grouped into three different

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groups.

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Here is the first group.

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Here is the second group, and here is the third group.

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Those are permissions for user read, write and execute.

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Next come permissions for group.

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Group is in second column and if a user wasn't assigned to a specific group, then group name will be

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the same as username.

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That's what we see here.

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Read, write and execute for group users and read, write and execute for all other users that don't

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belong to this specific group.

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For example, let's have a look at this line.

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In this case, user root user is able to read, write and execute this directory.

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Opt.

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Group users are able only to read this directory.

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They are not able to write, but they are able to execute.

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And same for all remaining users.

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They are able to read, not able to write and are able to execute.

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If I have a look at this line, it is actually root directory that is a home directory for root user.

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Here I see that this directory could be read, written and executed only by user.

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There are no permissions for other users in the same group or for other users from other groups here.

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Everywhere you see dashes.

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Let's have a look at those permissions for this std error dot txt file.

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It is a file.

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It starts with the dash.

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Next here you see user permissions read, write and not execute.

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Are the users in the same group are able only to read this file?

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They are not able to change it or execute and remaining users in other groups are also able only to

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read this file.

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I'll explain you how to make file executable a bit later when I'll tell you how to create your own shell

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scripts.

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And if you want to execute a specific shell script, you need to make such file executable.

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You need to change its permissions.

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We will get back to it a bit later.

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All right.

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That's all for file permissions and that's how you are able to distinguish between directories, links

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and files.

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All right.

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Next, let me explain you how you could see file size of every directory or file in human readable format.

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For that, you could use another option.

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Let's type ls l h h stands for human.

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Let's press enter.

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And now I see those sizes in kilobytes, megabytes and so on.

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Actually, in this case I see only sizes in kilobytes.

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But let me for example go into bin folder and enter same command there.

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CD bin and ls l h.

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And now I see some sizes in kilobytes.

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56kB.

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35kB.

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Probably there are some larger files.

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Let me go a bit up.

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Yeah.

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Here is an example of such file.

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This file is 3.4MB in size.

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Also a bit later I'll explain you how you could filter files by file size and how you could sort files

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in this output.

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Also, I want to show you how to use one more option.

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Let me clear terminal and go back to root directory.

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And here let me type LS dash capital F With this option you'll see actually types of all files and directories.

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And this ad means that it is a link.

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This forward slash means that here you see directory and if you don't have any forward slash or ad at

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the end of the name, then it means that it is simply a regular file like hello dot txt.

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This output is useful when you want to write this output, for example, to a specific file and inside

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of the file you will not see any colors like blue color, light blue and so on.

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Let me show you that quickly.

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For example, I could write this output into specific file.

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Let's say test dot txt.

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And if I'll read the contents of this file called Test.txt, I'll see actually the same characters at

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the end of every name.

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But of course, I don't see any colors because the text files store characters simply in C or other

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format.

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They don't store any colors at all.

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All right.

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Let me clear our terminal.

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And now let me show you another option.

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Dash LA with a option.

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You could also see hidden files and folders.

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And for example, here is hidden file, hidden files and folders in Linux.

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Start always with dot.

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If I simply enter ls l.

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I don't see this file here in this output, but with a option.

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I see such files and folders on the list.

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In this case there is a single hidden file.

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If I go to etsy folder and list all files and folders including hidden files and folders here, scroll

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up.

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And at the beginning of this output I see.

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Hidden file dot p.w.d. dot log.

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Again, without this option you will not see hidden directories and files.

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All right.

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That's all what I wanted to demonstrate you here in this lecture.

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And now you know how to distinguish between directories, files and links.

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They have different colors, at least in Bash Shell.

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Also, you know how to use such options as L A and H.

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With H option, you could find human readable sizes for all directories and files you are looking at.

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That's all for this lecture.

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And next, let me explain you how to create new files and folders.

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I'll see you next.

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Bye bye.