In At The Deep End - 2017-08-08

user228700

10:59 AM

@JohnR: Hi! :-) Are you around?

John Rennie

Hi there :-)

user228700

:-) I have a quick question about operating systems and thought you might be able to help!

John Rennie

Yes, of course.

user228700

Wokay. I was wondering exactly what Linux is; clearly, it has a GUI but it is also centered around command line, no?

John Rennie

The definition of what is and isn't an operating system is somewhat vague and differently people will draw the line in different places.

The GUI that you see is strictly speaking just an application called the shell

So for example with Linux you can have lots of different GUIs.

user228700

11:03 AM

@JohnRennie Yes, yes, in all operating systems, right?

user228700

> you can have

user228700

What do you mean?

John Rennie

What type(s) of Linux have you used?

user228700

None yet. So far, I have only learned a bunch of commands.

John Rennie

Have a quick scan through this article

Actually I should have used the term desktop environment rather than shell, as in Linux the term shell has more specific meaning.

user228700

11:07 AM

@JohnRennie I've read the introduction...

user228700

@JohnRennie And what is that?

John Rennie

In Linux shell means the command line interpreter i.e. when you type ls -l (or whatever) the shell is the program that takes what you've typed and does somethign useful with it.

user228700

Aha, this is exactly that which I'd meant to ask.

user228700

This isn't the case in Windows, no?

John Rennie

For historical reasons, in Windows the shell refers to the application that provides the GUI. In current versions of Windows this is the app explorer.exe

But we're getting a bit off the subject.

user228700

11:11 AM

Ah, I see. What would the general definition of the term shell be? (I've already read the Wiki page)

John Rennie

There is no general definition because Windows and Linux use the term differently. I'm not sure Apple Macs use the term at all ...

Though if they do they probably mean the same as Linux since OSX is based on a form on unix.

user228700

Ah, wow, I had thought that the term shell was common to all operating systems and that there must be a general definition.

John Rennie

To the extent that the term has a general meaning it means what it means in unix.

Windows is kind of the odd one out when it comes to operating systems because it came from a different background.

If you're asked about shells in an exam it will probably mean the unix shell.

user228700

Ah, hmm, I see.

user228700

Do you know of any place to practise Linux commands (other than the operating system itself)?

John Rennie

11:16 AM

I was about to say you can install a Linux subsystem on your laptop, but that may be Windows 10 only. I'd have to check.

user228700

Oh, wow, I can?

John Rennie

Windows Subsystem for Linux

Windows Subsystem for Linux (WSL) is a compatibility layer for running Linux binary executables (in ELF format) natively on Windows 10. Microsoft and Canonical partnered together to enable an Ubuntu image to be downloaded and extracted to the user's local machine, and for the tools and utilities contained within that image to run natively on top of the WSL. WSL provides a Linux-compatible kernel interface developed by Microsoft (containing no Linux kernel code), with user-mode binaries from Ubuntu running on top of it – a Bash shell and command language, with native Linux command-line tools (sed...

Ah yes, Windows 10 only.

user228700

Ah, dang :-/

user228700

I will find a place to do in online, then.

user228700

Thanks so much! :-)

John Rennie

11:19 AM

You started out asking exactly what Linux is

Have we covered that to your satisfaction?

user228700

@JohnRennie Well, yes, I was really only wondering about the shell.

user228700

@JohnRennie Certainly! :-)

John Rennie

Ah OK. Good :-)

user228700

Thank you! :-)

John Rennie

I wonder if it's worth installing Windows 10 on your laptop ...

user228700

11:21 AM

Hmm. Tomorrow, I will ask my teacher whether it's absolutely necessary for me to work with Linux. I will let you know what she says...

John Rennie

OK. Do you want to meet up this afternoon?

user228700

Yes! I am beginning to loathe my Physics lectures. I have bought the textbook and will come prepared with questions! :-)

John Rennie

I am beginning to loathe my Physics lectures - that's a shame ...

... speaking as a physics nerd :-)

user228700

It is, yes :-( What can I do, he does a very poor job.

John Rennie

What time do you want to meet up today, or have you not decided?

I have no special commitments so any time is fine by me.

user228700

11:24 AM

Same time as yesterday?

John Rennie

4 ish?

user228700

Yep. I will ping you around then if that's OK.

John Rennie

That's fine. I'll be here, probably arguing with 0celo7 about Riemann normal coordinates :-)

user228700

Hahaha :-) OK, have fun! See you then.

John Rennie

Bye (for now :-)

John Rennie

1:35 PM

Hi

user228700

Yes, HI! :-) I'm not ready to ask about Physics yet; I'm getting there but I've been switching back and forth between subjects.

John Rennie

No probs. I can do Linux commands :-)

user228700

Hehe. Wokay, so I've been practising on this website.

user228700

And I've got a few simple questions.

user228700

Firstly, I'm finding that I can't go to a directory nested inside another nested directory from the present directory.

John Rennie

1:37 PM

@Kaumudi.H ah, that's cool. I knew web sites like that existed ...

user228700

Is this truly the case or have I messed up?

John Rennie

I've just done that ...

user228700

No, no, I mean this: (Hang on, my internet is slow :-(

user228700

You know what I mean?

John Rennie

1:44 PM

Use pwd to show the current directory

user228700

It's in root.

John Rennie

OK, if you type ls -l that shows you all the files and directories in the current directory

so if you type cd level2 linux is going to say you ain't got no level2

user228700

Is it supposed to show nested directories? It shows level1, yes...

John Rennie

to go straight to the level2 directory use cd level1/level2

user228700

@JohnRennie :-P See, this was my question, whether it was possible to go drectly from there to level2.

user228700

1:48 PM

@JohnRennie Ah, OK. Understood! :-)

user228700

I have one more question! Am I not allowed to make files with names having multiple words?

John Rennie

I'm not sure if linux allows spaces in file and directory names

user228700

Because, see:

John Rennie

user228700

John Rennie

1:50 PM

Aha, it does!

user228700

O_O It does?

John Rennie

Look at the command I typed ...

mkdir 'level 2' created a directory called level 2 with a space in the name

What were you trying to do when you typed cat> ?

user228700

@JohnRennie Make a text file.

John Rennie

So to create the text file myfile you'd use:

cat >myfile
Line 1
Line 2
etc
now I'm bored

user228700

No, no, it should be my file, with a space. That's what I was trying to do.

John Rennie

1:54 PM

The use cat >'my file'

user228700

That's not working :-/ See above picture.

John Rennie

Works here ...

user228700

I don't understand most of what you've typed :-/

John Rennie

Do you know what the cat command does?

user228700

All my teacher told us is that it's used to make text files.

John Rennie

1:58 PM

cat just takes text from the standard input stream and prints it to the standard output stream

Do do you know what the redirection symbols > and < do in linux?

user228700

@JohnRennie My teacher mentioned them in brief.

user228700

Actually, never mind; I will try it again later on after having read up on cat. I'm going down to have dinner now but I will come back after having read (some more) Physics if you're still around.

John Rennie

OK, see you in a bit. I'm here all afternoon now. I'm currently playing with a new PC.

user228700

BTW, this arrangement really is helping! :-D

John Rennie

Good :-)

user228700

2:00 PM

@JohnRennie Aha, and what did you buy this one for? :-P

John Rennie

This isn't a laptop. It's a boring desktop that I'll be using for testing software. Very dull, but these things are necessary.

I've just finished installing Windows 10 on it.

user228700

Ah, I see, a PC.

John Rennie

Well laptops are PCs too

PC stands for Personal Computer

user228700

Right, but when one says PC, gah, never mind, my brain is dumb :-P

user228700

OK, have fun with it! :-) I'll see you.

John Rennie

2:03 PM

Bye

John Rennie

3:04 PM

BTW if you want to install Linux on a USB key see:

pendrivelinux.com/universal-usb-installer-easy-as-1-2-3

But you'll need to download a Linux ISO and they're pretty big. You might want to do that some place you can get a decent wireless connection.

John Rennie

4:02 PM

Hi :-)

user228700

Hi! :-)

user228700

Thanks for the link! I will do it when I go back home next month...

user228700

I wasn't able to get around to revising Physics, BTW. I decided that I had had enough (~4 hours) for the day and socialised a bit :-P Especially since I am now in college and all, haha.

John Rennie

Makes sense. It's a mistake to work too hard. You end up losing interest.

You don't want college to turn into the slog that revision was. That would be a real shame if that happened.

But I have a suggestion for you ...

user228700

One second, I will be right back.

Transcript for

♦ In At The Deep End