[MIT]计算机科学课堂中学不到的知识 The Missing Semester
$1
06:26 shell prompt
07:53 parameters are separated by space
create "hello world" or hello\ world to enter as a single para
10:25 env var
$PATH: linux/mac,use / to separate, all files lives in the root space(/开头）; win use \ to separate, lives in dif disc（开头是不同的盘）
which
12:54 relative path: to where you r right now, let computer find out themselves
pwd: find out where you are
cd: change current working directory
.:current direc
..:parent direc
cd .. : change to the parent direct
cd ./home: change to the home file under current direc
../../../../bin/echo world
ls: navigate through the directory
~: brings you back to home direc
cd -: cd to the previous direct
[cmd] --help: check out the function
19:21 flag(doesn't take in value) & option(takes in value)
20:08 ls -l /filename: longlist format display
第一个字母：direct
后面字母：3个一组，代表后面不同owner的权限（r读w写x执行）
23:10 对于文件夹来说rwx的意义
24:48 mv: change location/ change name （改前，改后）
25:27 cp: [copy file from, paste file to ]
26:05 rm: not recursive -rmf: recursive rmdir: remove the direc only when it's empty
27:05 man: find manual for a function
ctrl+L: clear & go back to the top
29:06 ways to rewire the input stream & output stream
cat: print out the file
30:58 another way to copy a file
- cp [old_file] [new_file]
- cat < [old_file] > [new_file]
>>:append
34:59 [input stream file] | [output stream file]: 前面的结果作为后面的输入（用来处理文本、图片非常好用）
35:51 root user: can do anything
sudo
#
sudo su
37:33 /sys
42:00 tee: 在文件里写，也在屏幕上打印
42:59 find
45:25 open files
linux: xdg-open
mac:open
