UNIX programming course on COURSERA

Some configurations before we get into main context

Quick Q&A

1. What's the default shell program on Windows,Linux and MacOS?

A: cmd, bash and zsh.

2.What is GUN/Linux?

A: some takeaways:

GUN/Linux is a more specified/accurate name rather than Linux; and the GNU org. wants to inspire the spirit of free software/freedom of usage or development
Linux is a kernel, functioned/activated based on GNU(GNU's Not Unix) OS; it cannot run with itself;
Linux is developed by GNU project;
Linux distributions is actually GNU/Linux distributions

FOR more details, see also in this website

We can install the windows subsystem for Linux(WSL) instead of using dual OS or virtual machine, which is a waste of a memory if there is not too much work on the shell.

Here is the difference between WSL1 and WSL2

difference

You need to click on this tab as you wish to install WSL in your Windows OS

image.png

Encounter problems? Here are some troubleshooter pages ：

Refer to this if you got trouble in accessing the Microsoft Store
refer to this for installation
this is the official guide

After successful installation, you can check the version

zsh --version

you can also see all shell that you got now

cat /etc/shells

You can also easily switch the shell :

chsh -s /bin/bash

chsh -s /bin/zsh

right now we may have many terminals, you can integrate them together with Windows Terminal, which supports cross-platform usages, including cmd/ubuntu/....

P.S.: control+L 另起一页！很有用啊

Unsolved Questions:

有什么不同？：在windows terminal中的cmd进入到wsl，我进入到的是window里面的文件夹 inorganicunix@inorganics:/mnt/c/Users/15290$ ，但是cd后会回到 /home/inorganicunix ；在wt里面打开Ubuntu也是一样。但是如果直接打开Ubuntu，不通过wt，那么初始所在的路径是在 /home/inorganicunix；在wt的powershell里打开也是一样。为什么呢？显示如下图

WSL over windows terminal

enter Ubuntu in Powershell over Windows Terminal

direct Ubuntu over Windows Terminal

direct Ubuntu

Fist Week Outline Notes

let's start with command line command

Every command line is like a little computer program; all command line commands all tend to have the structure like:

[command] [options] [argurments]

Options are preceded by a hyphen(-); arguments can be like files/raw data/directory.

-Navigating the command line

hierarchy of folders("directories" in Unix)

home directory(includes personal files) $\equiv$ "~"

path(highlighted):

what a path looks like in the tree diagram

Here are some basic commands

cd

pwd

ls

cd .. //go back to the upper dir.

Let's applied them in real senario.

We can change directory into any folders can be typed(absolute path) exactly in the [arguments] with "~/[directory]"

cd ~/Music
pwd
## /user/inorganic/Music

If you are not sure about what you wanna enter, and have no idea that what is in the current folder, you can try pressing the Tab;

cd ~/

(double) press the Tab to see what is inside of the selected folder

cd ~/[seletced folder] //press the tab 
## ## Desktop
## Documents
## Photos
## Music
## todo.txt       (just an example here )

If you want to find the file/folders which is led with some characters, for example, ".vim", you can type "cd ~/.vim" then press Tab to find the specified one.

inorganicunix@inorganics:/mnt/c/Users/15290$ ls ~/

.123.txt.swp               .landscape/                .viminfo                   zsh-syntax-highlighting/
.bash_history              .motd_shown                .vimrc
.bash_logout               .profile                   .zcompdump
.bashrc                    .sudo_as_admin_successful  .zshrc 

inorganicunix@inorganics:/mnt/c/Users/15290$ ls ~/.vim
.viminfo  .vimrc

Summary

You can identify a specific file or folder by its path.
The root directory (/) contains all of the folders and files on your computer.
Your home directory (~) is the directory where your terminal always starts.
Use the cd command to change your working directory.
The pwd command will print the working directory.
The ls command will list files and folders in a directory.

-Creation and Inspection

mkdir i.e, make directory

let's try it! Remember that the "Code" here is an [argument] phrase.

inorganicunix@inorganics:/mnt/c/Users/15290/My Documents$ ls
'My Music'  'My Pictures'  'My Videos'
inorganicunix@inorganics:/mnt/c/Users/15290/My Documents$ mkdir Code
inorganicunix@inorganics:/mnt/c/Users/15290/My Documents$ ls
 Code  'My Music'  'My Pictures'  'My Videos'
inorganicunix@inorganics:/mnt/c/Users/15290/My Documents$

The most simple way to create a blank file is using the touch cmd;

Sometimes it's to complicated to distinguish the files and directories with a single ls cmd, then the [-option] function can specify our needs.

ls -l

Let's be coherent.

inorganicunix@inorganics:/mnt/c/Users/15290/My Documents$ cd Code
inorganicunix@inorganics:/mnt/c/Users/15290/My Documents/Code$ touch ablankfile2.txt
inorganicunix@inorganics:/mnt/c/Users/15290/My Documents/Code$ ls
ablankfile2.txt
inorganicunix@inorganics:/mnt/c/Users/15290/My Documents/Code$ ls -l
total 0
-rwxrwxrwx 1 inorganicunix inorganicunix 0 Nov 30 13:54 ablankfile2.txt
inorganicunix@inorganics:/mnt/c/Users/15290/My Documents/Code$

-rwxrwxrwx is a long sting combined with 10 characters, which stands for different meanings correspondingly.

The first character represents the attributes of the file/dir.; the following three blocks correspond to the authorities ofOwner/ Members_of_group_that_owner_in/ Others

Here is a completed instruction for dummies.

Now if you want to see the detailed info of a specific file, such like we have already created just now, try this. (I've type in some meaningless words in the file)

inorganicunix@inorganics:/mnt/c/Users/15290/My Documents/Code$ wc ablankfile2.txt
  5  19 117 ablankfile2.txt

The first "5" is line; "19" is the total words;"117" is total characters.

let's create a text file with a long content, which is a usual scenario in the real life cases, literally, TLCR :(

inorganicunix@inorganics:/mnt/c/Users/15290/My Documents/Code$ touch Homeric_Hymns.txt
inorganicunix@inorganics:/mnt/c/Users/15290/My Documents/Code$ vi Homeric_Hymns.txt
Error detected while processing /home/inorganicunix/.vimrc:
line    2:
E492: Not an editor command: rscheme ron
Press ENTER or type command to continue
inorganicunix@inorganics:/mnt/c/Users/15290/My Documents/Code$ cat Homeric_Hymns.txt
Homer, Iliad, Book 1, lines 1-52

Sing, goddess, the anger of Peleus? son Achilleus........
.................
.................

I create a file includes an excerpt of Homeric Hymns, just try to implicate demonstrate a very large text file that can hardly read. See how the following commands make an entrance.

Use wc to incept the basic info.

inorganicunix@inorganics:/mnt/c/Users/15290/My Documents/Code$ wc Homeric_Hymns.txt
  54  577 3119 Homeric_Hymns.txt

Hum, that's a big one isn't it?

If we simply use the cat to get all the content, too long to acquire the key point that we want. head is for showing the first 10 lines, we can also set it manually, with the option -n 5 behind, meaning get the first 5 lines. cat -c 50is for asking the first 50 words, and similarly, you can deduce the tail and less.(less would take over your entire terminal window)

You can also refuse to use vi as there is only one line to insert in a (new) file, if you find it tooo noxious to open up vim editor, echo.. >..and echo.. >>.. are here for you. That also omit the create-file process for you.

inorganicunix@inorganics:/mnt/c/Users/15290/My Documents/Code$ echo "this line was echo into the file echo-out" > echo-out.txt
inorganicunix@inorganics:/mnt/c/Users/15290/My Documents/Code$ ls
Homeric_Hymns.txt  echo-out.txt
ablankfile2.txt
inorganicunix@inorganics:/mnt/c/Users/15290/My Documents/Code$ cat echo-out.txt
this line was echo into the file echo-out

As you can see, a now file named by you with echo is also created simultaneously. This technique is called output redirection.

One easy way to create a file is using output redirection. Output redirection stores text that would be normally printed to the command line in a text file. You can use output redirection by typing the greater-than sign (>) at the end of a command followed by the name of the new file that will contain the output from the proceeding command.

You can use cat ..>>.. to insert/append a sentence at the end of the content.

inorganicunix@inorganics:/mnt/c/Users/15290/M
y Documents/Code$ echo "this line was appended "nics:/mnt/c/Userecho "this line was appended
into the file echo-out.txt by 'echo >>' techui
que" >> echo-out.txt
inorganicunix@inorganics:/mnt/c/Users/15290/My Documents/Code$ cat echo-out.txt
this line was echo into the file echo-out
this line was appended into the file echo-out.txt by 'echo >>' techuique
inorganicunix@inorganics:/mnt/c/Users/15290/My Documents/Code$

WARNING!!

IF you want to append another line to the end of echo-out.txt, so typed echo "A third line." > echo-out.txt into the terminal when really I meant to type echo "A third line." >> echo-out.txt(notice I used > when I meant to use >>). The previous content would be covered by the current inputs.

-Text Editor

vim and emacs // two prevailing text editor in the world.

UNIX programming in the first chapter