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Linux like any other operating system, almost any other operating system,

is going to provide you with a file system.

A set of directories or folders if you call them that, and

files inside those directories.

And there's basically a hierarchy of these folders,

directories with directories under them.

Eventually, you get files underneath all those, right?

Now, you see this in every operating system, Windows, MAC OS,

Android, whatever.

You see a file system.

Note that a system without an operating system like Taka or

Arduino, it doesn't have a file system, right?

Even though you have, if you have data inside of memory, like an E prompt or

something like that, you want to write to the E prompt and read from it.

You can write raw data, and read raw data, but you just give raw addresses.

You say I want to write to address zero, this data.

Address one, that data.

You don't have a file system with names and a hierarchy,

convenient names and hierarchy and directories and

all that and you don't have that without an operating system.

So that's one of the things an operating system provides is a file system.

Now it's always a hierarchy so

use these back slashes to separate the different parts of the path.

So the path, is basically the list, the hierarchy path, the path through

the hierarchy through all the directories concatenated together into the path.

And that, the path is the entire name of the file.

So the file will have a name, a local name, but

it's path will list all the directories above it, from the top.

So, in Linux, the top level directory's called backslash.

So you can see in our picture, you got a backslash right there.

That's the top level, highest level directory.

And under that, it, on my resvpi,

I've got four sub-directories under that, bin, etc, home, and user.

Then, under the home directory, I've got another directory called pi.

And under the pi directory, I've got three mores directories,

desktop, indiecity, and python-games.

This is what my file system hierarchy looks like.

And then, actually, as I'm working,

I make, I have a bunch of files on the desktop.

So on the desktop, I would have a set of files, the actual files that I've made and

stock on the desktop.

There is this file system hierarchy and you have to be able to traverse this

hierarchy in order to access files, to use different files inside your system,

to run them and execute them, and modify them and so on.

So that's sort of a basic feature in any operating system

is to allow you to traverse the hierarchy of the file system.

So, let's say we wanna do this from the command line.

We're gonna do it in our text-based interface.

So, first thing you wanna know is the pwd command.

Pwd tells you what directory you are currently in.

So, when you've got a terminal running a shell,

that terminal is gonna be in a particular directory.

It has a directory that is sitting in, that is looking in.

And you can change that directory but

it's always gonna start off in some default directory.

And you can move up and

down through the hierarchy, but Pwd tells you where you are in hierarchy right now.

So if I type Pwd like I do here, it says /home/pi.

So that tells me what directory I'm in right now.

Now, so I tell them /pi.

And so if I make a file right now, it would appear in that directory.

If I delete a file, it will delete it from that directory and so on.

All right, so it just reports the directory that you're currently in.

Thank you.

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Lecture 1.3 - Linux Filesystem

树莓派（Raspberry Pi）平台及其 Python 程序设计

与讲师见面