[Youtube学习笔记]Linux的50个实用指令

[Mengkelyu]

50 Most Popular Linux and Terminal Commands

这篇文章的内容主要来源于Youtube视频The 50 Most Popular Linux & Terminal Commands - Full Course for Beginners
建议大家可以follow一下这个博主来支持。

另外，推荐这个网站 Linux Commands Handbook，里面有可以查询的Linux指令。

为什么要掌握这些指令呢？

• 更好地控制你的电脑
• 运行速度很快
• 可以自动化很多工作

操作系统

Linux和Mac都来源于一个叫做Unix的操作系统，因此可以指令基本是通用的。但是Windows有一套自己的系统。
Linux本身是指一个Kernel, Kernel就是链接application和CPU / Memory的东西。

在Windows上安装LInux

windows一般是不可以直接用Linux指令的，但是现在我们可以用下面的命令来在Windows里面安装一个小的Linux系统。
wsl --install

电脑上用管理员权限运行 PowerShell （不是 PowerShell(86) ）

重启电脑后就可以搜索到一个叫做Ubuntu的程序

打开这个程序后，需要自定义用户名和密码（用户名需要是小写英文）
然后就可以在这里运行Linux指令啦

为了更好地运行这些不同的Shell，可以安装一下Windows Terminal。（免费软件，在Microsoft Store里面可以安装）
安装后，它可以允许我们自定义运行命令的背景等等。如果我们要运行一个Windows Powershell，可以点击加号，有不同的Shell可供选择

Basics

一些基本指令

whoami 'print the username
man <command> 'open a manual for that command
man whoami
clear 'clear the terminal screen
clear -x 'clear the terminal screen but remains the history
pwd 'print working directory
ls 'list a contents of the current folder
ls <target folder path> 'list the contents for a target folder

ls -l 'long format of files. (with file names etc)
ls -a 'does not hide files starting with .
cd 'change directory
cd .. 'Go back to previous folder
cd ~ 'Go to the folder with username
help <command> 'the help file for any command

Linux File Structure.

All absolute path starts with /

In the home folder, for all users using this machine, there will be a username for him/her

mkdir #make a directory 创建一个文件夹
mkdir a b #make two folders 创建 a 和 b 两个文件夹
mkdir -p a/b #create parent directory when necessary 在文件夹 a下创建文件夹 b, 如果文件夹a不存在，先创建文件夹a，再创建子文件夹b
touch #change file timestamps. if a file does not exist, it creates this file for us 改变文件的时间戳，如果文件不存在，创建这个文件 (这个命令常常用于创建文件)
rmdir #remove a directory (only for empty ) 删除空文件夹
rm #remove a file 删掉一个文件
rm -rv <folder> #recursively delete all files in a folder 删除文件夹中的所有文件
rm -V #print the output V参数可以输出删掉的内容
open #open a file or folder (mac only) mac中打开文件或文件夹的指令
open . #open the current directory 打开当前文件夹
xdg-open #open command in linux 打开文件在Linux中的指令，会用默认软件打开
mv #move files 移动文件
cp #copy a file or folder 复制文件或文件夹
cp -r #copy recursively for files in a folder 复制文件夹以及其中的所有文件
head #output the first part of files 输出文件的前部分
head <filename> -n <number> #n is for the number of lines to output 
tail #output the last part of files 输出文件的后部分

date #prints out the current date 输出当前日期 
date > today.txt #output the current date to today.txt 输出当前日期到文件today.txt
date >> today.txt #appending to a file instead of rewrite it 输出当前日期，并把当前日期写在today.txt文件后面，而不会删除原本内容

[Mengkelyu]

cat file #print all contents of a file 输出一个文件中的全部内容
cat file1 file2 #print all contents of file1 and file2 输出文件1和文件2的全部内容
cat -n file1 #-n is to print out the line numbers 加入参数n，可以同时输出内容和行数
less <file># it shows the content stored inside a file, in a nice and interactive UI； cat的漂亮形式
echo #it prints to the output the argument passed to it 这个命令等于print
wc #print number of lines; number of words; number of bits 输出基本信息，（多少行，多少数字，多少bit）
|  #give the output of the first argument to the second argument 这个符号可以把符号前面的Output传递给符号后面的命令作为Input
ls -l | wc #word count for the ls -l 比如这个例子，ls -l 输出了当前文件夹下所有文件的名字，然后这个文本传递给了wc输出文本的基本信息
sort #sort the document 给文件排序
sort -n file #sort everything numerically 按照数字顺序给文件排序
uniq #report or omit repeated lines
uniq -d #only report duplicated values
uniq -u #only report non-duplicated values
uniq -C #count how many times each value is duplicated
*.txt #match all documents ending with txt
? #match one character
{a,b,c}.txt #output a.txt, b.txt, c.txt
Day{1..365} #output Day1 Day2 Day3 .... Day 365
diff #compare the contents of two files
diff -v file1 file2 #compare two files line by line
find <directory> <critria>
find . -name #*.txt#
find . -iname #*.Txt# #i for case incensitive
find . -type d #only search for directory
find . -type f #only search for files
find . -name #E*# -or -name #*E# 
find . -type f exec cat {} \ #exec cat to every file.  {} is placeholder for each found result
grep #help search inside files
grep <string to be found> <text to search>
grep -r <string to be found> <directory> #recursively found a string in all texts in a folder. -ri can make it case incensitive
du #find the size of directories or files
df #show how many space left
history #history of all commands run. Combined with grep, it is possible to obtain the command with certain character 
ps #view the process running on the computer
top #display top 10 process
kill #shut a process
kill <PID>
kill -9 #brutal kill
kill -15 #gental kill
killall #perform multiple kills
jobs #print out commands 
fg <job number> #run some command on the foreground
bg <job number> #run some command on the background
<command> & #run the command on the backgound
jobs #see those commands
gzip <file name>#compress a file
gzip -k <file name> #compress a file while keeping the original file
gzip -d <file name>#decompress a file
gunzip <file name>#decompress a file
tar #used to create an archive, grouping multiple files in a single file
tar -cf archive.tar file1 file2 #the c option standas for create, the f option is used to write to file the archive
tar -xf #extract to current folder 
tar -czf archive.tar.gz file1 file2 #creating a tar achive and then running gzip on it
nano #a friendly editor
alias <new command name> = '<old command>'# Give some alias to a long command
# difference of "" and '', "" allows variable in a string
echo "home directory \$PWD" # 这里\$PWD被当作成了变量或参数
echo 'home directory \$PWD' # 这里\$PWD没有被当作成变量或参数
xargs # turn the output of first argument to the input of second arguement'
find x -size +1M | xargs ls -lh
ln # it is used to create links. Links are effectively a pointer to another file
# Two types of links: hard links and soft links
ln <file1> <file2> # create hard link to file1 
ln -s <file1> <file2># create soft link
# soft link will be removed when original file is removed. But hard link will not be removed