Lecture 1: Course Overview + The Shell (2020)

[@litchyarn]

6:04 shell prompt 6:32 curstermizing shell 7:03 $date 7:19 $echo 7:29 $echo hello 7:46 $echo "Hello world" 8:41 10:01 environment variable 10:17 $echo $PATH 11:01 $ which echo 12:30 relative path 12:50 $pwd (print working directory) 13:24 cd /home (change my directory) 13:58 dot 15:03 ../../../../../ 16:20 $ls 17:15 ~ tild 17:36 - dash $ cd - 20:09 d means directory 21:32 read, write, execute 24:32 mv (rename, move) 25:20 cp (copy from, to) 25:50 rm (remove) 26:15 rmdir, mkdir (remove directory, make directory) 26:50 man (manual) 27:55 Ctrl+L (clear shall) 28:30 input and output 29:30 $echo hello > hello.txt 29:59 $cat hello.txt 30:10 $cat < hello.txt 30:43 $cat < hello.txt > hello2.txt 31:15 $>>^C 31:50 pipe 32:20 tail $tail -nl $ls -l / | tail -nl $ls -l / | tail -nl > ls.txt 33:35 curl curl --head --silent google.com curl --head --silent google.com | grep -i content-length curl --head --silent google.com | grep -i content-length | cut --delimetr = ' ' -f2 36:39 $sudo (super user) 38:02 $cat brightness $sudo echo 500 > brightness

[@heyitsme-y8f]

Jeong Rita thanks man really helps

[@lucaban]

this needs more upvotes!!!

[@Mainmenify]

Well done! this absolutely needs to be added to the video description to show timespamps on the video progress bar!!!

[@DrHusseinAlOmari]

Thank you! Very useful!

[@hingsli7245]

good job man, very helpful!

[@samdavepollard]

i'm old; i graduated in 1979, way before the www was a thing the fact that i can hop onto youtube and drop into a class at MIT like this still blows my mind

[@upstatenetworks4639]

Similar. EE/CS 1980's We've passed files back and forth for decades. Our development projects now involve 10's of programmers. This lecture was well presented and gratefully received. Nice Job and Thank you!

[@edvaned8207]

Similiar too. i graduated in 2004 😁

[@ShivangiSingh-wc3gk]

I feel so dumb at work sometimes. I had to learn these things the hard way, thank you for putting this out there.

[@xBugzilla]

But #! is a special comment, not telling the shell to run as root, right? I don’t get your comment or maybe I missed the part he explained shebang

[@resulhangeldiyev4427]

thank you youtube algorithm for this magnificent content

[@fedeac31]

I think we should rather thank MIT. They're quite probably the best tech university in the world, and they're publishing content for free that they could charge us a fortune to access if they wanted to.

[@middleverse3838]

I'm like 15 minutes in, and I'm already thankful to you guys for making this!! For someone who used to be a programmer but left and is now making a comeback, this packs-a-punch.

[@yixe2253]

These lecture are amazing, thanks for releasing this to the public!

[@ChristopherOkhravi]

This.

[@skarasif]

@@ChristopherOkhravi lectures ;-)

[@v1r47]

@@skarasif lectures* :-)

[@driden1987]

@@ChristopherOkhravi are you planning on coming back to creating videos on YT? Really wanted to see how your VIM series would pan out. Thanks for everything

[@térrence369]

Very true

[@Milbrown_Worker]

Im sad this kind of quality instruction is not commonplace across other post secondary institutions.. I guess it is MIT after all... Thanks for making this available

[@yousifabdulhussein]

This type of quality instruction isn’t even commonly available at MIT lol.

[@dhruvgupta8751]

the xdg-open in powershell was just: start worked with pdfs and .html files.

[@tamat]

I cannot thank you enough for this course. Im also a teacher at the university and I never have the time to teach this concepts deeply to my students, so at least now I have a place to redirect them.

[@advitiayanand5974]

glad to hear there's teachers that still care.

[@loremipsum7513]

THIS IS WHAT WE ALL NEEDED. THANK YOU FROM THE BOTTOM OF MY HEART.

[@infinite-journey]

Lectures we didn't ask for but we all needed the most.

[@JasonSFuller]

40:24 Please don't teach people "sudo su" (or the slightly less terrible "sudo su -"). In fact, don't teach people about "su" at all, other than to use it to install/fix "sudo" or as a history lesson. It certainly _works_, but you're telling the shell to do something twice, i.e. "run as root" (sudo) then "become the root user" (su). The thing you want is "sudo -i" or "initial login" (equivalent to "su -" and "sudo su -"), which tells sudo to start a shell *and* process the normal login scripts, e.g. .profile, .login, .bash_profile, etc. "Su"ing twice has a number of unexpected and irritating--though not insurmountable--side-effects for administrators (i.e. me, a linux admin for 20+ years), but it also causes trouble for an end-users since it strips their environment variables. "Sudo" handles this quite well (depending on your sudoers configuration), but "su" does not. This is problematic for things like preserving a non-root user's $SSH_AUTH_SOCK (maybe you want to use your ssh keys when you're root), or language preferences ($LANG), or $DISPLAY for GUI users, etc.

[@adammoore6594]

Thanks, that is useful :)

[@mwat56]

In case you need a shell (to do more than a single command) you'd call: sudo bash That avoids the problems mentioned above.

[@JasonSFuller]

@@mwat56 I'll politely disagree here. "sudo -i" does, in fact, give you a shell, AND it simulates a login the proper way. "sudo bash" suffers from the same environment problems as "sudo su"

Exactly. I was going to comment this, but you explained it much better than I could.

[@aram535]

If you don't need to go through "login" then 'sudo -s' will also work and just start up a new environment rather than login then env. For example 'sudo -s' will drop you into a root shell and 'sudo -u foo -s' will drop you into a shell for user 'foo'. Again without the login (.profile & .login). I recommend using "sudo -c 'command'", "sudo -s" and "sudo -u foo -sH" (-H sets the homedir for the user as well).

[@Chr0nalis]

I've been writing "clear" instead of just ctrl+l all this time ..

[@love.ly.]

Teymur Azayev same 😮

[@wolfram77]

is there a shortcut to clear scrollback too?

[@rabingaire]

same here

[@aavocadoToast]

Same

The clear command and ctrl+l do not do the same thing. They are very similar, but sometimes it makes sense to use one or the other.

[@MRainH]

《Lecture 1: Course Overview + The Shell (2020)》视频主要对“计算机科学教育缺失的学期”课程进行了介绍。涵盖课程结构、工具及教学方式，重点讲解了 shell 的基本用法，如命令执行、环境变量、路径操作和文件查看操作等。还介绍了命令行中的重定向、管道和 root 用户相关操作，以及一些实用命令，包括文件操作、文本处理、亮度调节和查找文件等。同时提到了课程作业和答疑安排。 [00:00] 课程概述及 Shell 介绍 [00:02] 课程介绍，讲解 Shell 等工具用法及课程安排 [03:49] 本堂课将介绍 Shell 的基本用法 [05:51] 打开终端，介绍 Shell 提示符 [07:02] 执行程序示例，如执行 date 和 echo 程序 [08:26] 解释空格分隔参数及创建目录示例 [09:39] 环境变量与路径操作 [09:39] 视频介绍课程并讲解 shell，此部分为环境变量与路径操作 [10:16] 介绍环境变量，echo $path 展示机器上的路径 [11:12] Linux 和 Mac OS 路径用斜杠分隔，Windows 用反斜杠 [12:49] 相对路径相对当前工作目录，可用 PWD 查看 [16:53] LS 可列出当前目录文件，也可列出指定路径文件 [19:22] 文件操作与常用命令介绍 [19:22] 课程介绍 shell 及文件操作与常用命令 [19:43] 介绍 LS -L 用法，展示更多文件信息 [20:02] D 开头表示目录，后续为文件权限 [21:31] 解释文件和目录权限的不同含义 [23:48] 介绍其他命令如 MV、CP、RM、make [26:58] 介绍 man 命令查看其他命令手册 [27:56] 提到 shell 组合程序及流的概念 [29:06] 命令行重定向与 cat 命令示例 [29:06] 课程介绍命令行重定向及 cat 命令示例 [31:02] 介绍命令行重定向追加功能 [31:51] 讲解命令行管道功能 [35:37] 介绍 root 用户概念 [36:51] 说明 sudo 命令及特殊文件系统 sysfs [38:45] root 用户操作与文件权限问题 [38:45] 介绍课程并讲解 shell 基本用法 [40:22] 介绍通过 sudo su 进入 root 终端 [42:30] 探索文件系统及介绍 find 命令 [45:03] 介绍 xdg-open 打开文件方法 [46:22] 预告下节课内容及作业安排

[@shreyaskali]

great! MIT never ever dissapoints me. Hope this quality of education become a standard in the future in every country.

[@potatomayo-haha]

43:44 scroll lock is for you to scroll around in spreadsheet program like Excel with arrow keys. so when it is toggled, arrow keys scroll around instead of move the focus on a cell

[@wolfram77]

that is also what ctrl+arrow keys do in a text editor. thanks for sharing.

[@walkastray007]

I'm actually tearing up. I've been trying to learn how to do things and it's been super frustrating and EVERY SINGLE COURSE I have ever seen either teaches you what a variable is. Or has a "google is your best friend" sort of approach. Thank you so much for making these videos

[@mrmusicdu74]

Why is this in my recommandations and why am I starting to plan to watch the whole courses

[@qwerty-wt5dr]

+1 I even dont have Linux installed for years

[@comments_very_nice]

same!

[@aalbero]

long live KZbin recommendations

[@sadeepthabandara8117]

If you haven't already, go for it!

[@overglobe]

😂

[@cosmos1701]

How they teach and covers the topic is really helpful. I think they are doing great work to post these and their notes over internet for people to use. Regards to the authors.

[@wizard7314]

41:30 it was worth watching for me, just for this. Great example of why 'cat' with shell piping isn't sufficient to write to a system file. But you also don't want to elevate the whole shell to root privileges because it's inconvenient (especially when scripting) and because then everything will be executed with root privileges. Now I understand why tee exists. Cheers.

[@StankyPickle1]

I wish this lecture series existed 6 years ago. Would've made life a little easier.

[@surered4958]

I cannot believe how good of a professor this guy is. I wish I could learn software development and data science from him.

[@glizzdawiz]

He has his own KZbin channel, which I just discovered kzbin.info/door/_iD0xppBwwsrM9DegC5cQQ

[@koraytugay]

Starts at 4:08

[@saki709]

cheers man

[@Hilaire_Balrog]

Thanks. Those late student were annoying me.

[@mustafaerdem140]

Tesekkurler

[@梨花风气正清明]

I would like to express my gratitude to the teachers and school who taught the course. Additionally, the authors translated the course into various languages and posted it online as notes, which helped us learn better.

[@seonginna8804]

This is a lecture series I have wanted. Thank you MIT!

[@NoxmilesDe]

The Website with text and everything to ALL those lectures is here: missing.csail.mit.edu/ Thanks to everyone who made this possible. :)

[@MissingSemester]

We also link to the relevant lecture notes in the description for each video :)

[@rabingaire]

I love how this guy explains things, I am a long time subscriber of his channel his voice is just mesmerizing

[@linsanity626]

Rabin Gaire same! what's his channel name?

[@rabingaire]

@@linsanity626 channel link kzbin.info/door/_iD0xppBwwsrM9DegC5cQQ

[@EndrChe]

This is the most beautiful thing I’ve ever found on KZbin...

[@sciberbee]

I came to think again, that we are living very hopeful period of time given that these fruitful and friendly lectures from MIT is ready to be watched free, at all around the world:)

[@lautoka63]

A good thing to be doing. I used to do something similar in my airline engineering career by running lunchtime classes for new young engineers. Much of the time people assume that others know as much as they do, without thinking how long and hard it was to acquire that knowledge.

[@yanlin9130]

Pretty good lecture, I wish it would be available when I was a freshman five years ago. Thanks for the hard work.

[@garysantos7053]

Just a note of added confusion: Apple replaced "bash" with "zsh" as the default shell in macOS Catalina While a number of Mac developers have already moved on to even more modern shells like Fish, zsh is more compatible with Bourne shell (sh) and mostly compatible with bash. THE VERGE/ By Tom Warren@tomwarren Jun 4, 2019, 4:27am EDT

[@xrafter]

Bash and zsh have the same syntax.

[@edavar6265]

Another resource I can reccomend on this topic is Learn Enough Command Line To Be Dangerous. It is a fun read with exercises.

[@bsko_turbo]

what a great and generous idea to publish these lectures for everyone. Thank you!

[@Kruglord]

Hey, that's Jon Gjengset! He does the "Crust of Rust" videos here on KZbin, I had no idea he also taught these lectures, I only recognize him now after coming back again 2 years later.

[@aavocadoToast]

Absolutely amazing lecture. I already knew 80% of these commands but it was still fun to watch and a good learning experience. Especially the fun stuff with sys directory in the end. Nobody teaches that lol...

[@meghasharma1962]

Hey, does it require linux or we can do in windows?

[@surplusvalue3271]

same!

[@surplusvalue3271]

@@meghasharma1962 maybe use WSL, though i don't know how are dirs organized in wsl

[@fedeac31]

This is awesome. You guys are awesome for sharing it publicly. Everything about this is awesome.

[@jasonkwan4814]

I wish it would be available when I was a freshman one years ago. Thanks for the hard work.

[@ZhengQu]

It is never too late :)

[@jitpackjoyride]

lol, I was a freshman 4 years ago and much more experienced now and I’m still going to sit through these lectures 🤓

[@henryluo9380]

Thanks for sharing it. It's really helpful to someone like me who have never learnt these basic things.

[@euriskoo]

8:03, Actually the program doesn't treat the string as one argument, it same as using double quotes, it's still an array of arguments.

[@gaomingt]

22:40 Also, if you don't have write permission on a file but have write permission on its directory, you can still delete the file.

[@alexandrechen3081]

This is exactly what I need! Thank you MIT

[@kortaffel]

40:30 you don't need to "sudo su". A simple "su" is suffice. "su -" if you want to get rid of enviroment variables and a login shell

[@kwangee]

About the "echo 1060 | sudo tee brightness" command 42:17 , does this mean if we somehow run a malicious .sh script obtain from internet that contain similar command but does malicious action, it will execute successfully? since this command does not require shell login as superuser

[@МихаилЧертушкин-я2с]

Amazing to look at it during quarantine. Thank you very much!

[@majoragan]

Just finished first lecture... Big thanks for this series!

[@Qladstone]

After several years of watching lectures in my off-work hours, this shall be my "graduation" class.

[@metroboomin8895]

tip: watch on 1.5 speed if it suits your fancy, i find it helps me focus (also great lecture!!)

[@shubxam]

Thank you so much for releasing this course in public. Just been through 1st lecture and content and the way you teach is very good.

[@nairorokidul]

Another not obvious thing: Inside the shell CTRL + C is cancel, not copy. The most useful trick noone tells you is hitting the up arrow offers you the latest command you entered, and you can scroll up as much as you want by hitting up arrow.

[@spatialnasir]

Use Ctrl + Insert to copy Shift + Insert to paste

[@steveroger4570]

This is better than my entire degree in my uni

[@popluss]

wow, this is very good! the content is really nice and the way he teaches it and structure the lecture is way better than what i had in college

[@shelinesim1038]

"On Windows, who knows?" made me chuckle

[@pedrofalcao1900]

Made me install linux

[@ze_kel]

​@@pedrofalcao1900 try WSL it's super easy to setup and you get full linux terminal inside your windows.

[@HendersonHarrisson]

WSL easy bash without switching OSes

[@casedup]

Great Great Great! Been using bash shell foryears and you opened me up to other worlds man. These videos are so 👍

[@edgrimm5862]

Most of the stuff under /sys/class/ are indirect links to the directories that have the actual stuff. By default, find does not follow symlinks. If you search from /sys/, you'll probably find brightness under kernel, devices, and modules.

[@mrbeats7434]

Very good. This teacher is first class. Thanks so much

[@EarthB00]

These are super useful. Making my way through them.

[@adjusted-bunny]

How can you run "tee" as root (sudo) because it is not an ordinary program but a shell utility like ls? In my logic you would need a root shell, too. I'm confused.

[@stardusts42]

FYI, you can drag and move the subtitle from the bottom to other places until the instructor types "Ctrl + L"

[@clanoftheducks1850]

You probably want to explain su stands for substitute user not super user, which is a common misconception even in the Linux world, but su let's you go into a shell for another user, not just the superuser, hence the name.

[@ir23000]

42:50 find command does not work because you didn't specify the directory to search in (you probably wanted to type "find . -type f ... " )

[@MissingSemester]

Ah, no, find defaults to the current directory (not on macOS though). The issue was actually that find does not follow symlinks by default, and /sys is full of them :)

[@ir23000]

@@MissingSemester ah tnx, didn't know that :) I used to need to specify dir on my system.

[@mtomazza]

@@ir23000 me too.. like . or /

[@sayanghosh6996]

11:10 no, if you run echo you actually run the shell builtin echo, not the one at /usr/bin/echo. `type` is better than `which` in this regard

[@takreem.akhter]

Thank you youtube recommendations. This was beautiful! I am going to watch the whole course.

[@MubashirullahD]

This entire talk is this smart telling you you don't know things. :)

[@sriranganayakulu8513]

Thanks MIT!! For these great lecture series

[@ConorJTobin]

Am I being pedantic to ask about 18:53? When Jon says that "there is an optional number of options," does he mean a number of optional options? I guess zero would be an "optional" number of options we could apply, no?

[@DutchmanDavid]

`which` and `where` were important for me that one time I tried to (roughly) time a short piece of bash script. For some reason `time` did *not* want to accept some parameters I gave it. Turns out I was using the `shell reserved word`, not the *time* program that also exists in `/usr/bin/`. Executing the next gave me info on why my script didn't work: > which time time: shell reserved word > where time time: shell reserved word /usr/bin/time This showed me I just needed to add /usr/bin/ in front of the command to fix my troubles.

[@jerrys5387]

I hope my univ could have such courses, instead of assuming we already know

[@sportsfreund8430]

God damn, I had this bookmarked for way too long. Looking forward to going through the playlist! :)

[@arytiwari3789]

37:00 couldn't cd to sys in my mac. why so? no such directory found

[@thengc]

On the exercises #6: Run the command by explicitly starting the sh interpreter, and giving it the file semester as the first argument, i.e. sh semester. Why does this work, while ./semester didn’t? What's the reason for this exactly? Why does sh have permission while a simple ./ cannot execute the file?

[@justlogyup]

I *think* that's because you don't have execution permission on that file so you can't run it directly. but when you use sh, it reads the file and interprets the commands within, so not actually executing the file. from sh's manpage: The shell is a command that reads lines from either a file or the terminal, interprets them, and generally executes other commands.

[@meojunior]

I really enjoy this course and learn a ton of foundation things. Thanks guys

[@priteshugrankar6815]

This is truly amazing!! Thanks for sharing!! By the way, I see vendor Perl and core perl in the path at 11:40. Does it mean the instructor is using Perl? If so, for what purpose?

[@dellmdq]

# to run command as root. * head explodes * Doing my first steps on Debian Thank you, thank you, thank you for these lectures!

[@maksimbronsky7117]

On Windows the adequate command for xdg-open is simply explorer.exe :-)

[@ramprax]

You can use 'start ' instead of explorer.exe

[@LearnWithBahman]

Note that sysfs does not exist on Windows or macOS. I also could not find sys in Mac.

[@fhajji]

I don't know about MacOS, but since it is FreeBSD-based, I would try 'sysctl' instead. It is a program though, not mapped like a file system.

[@sameednaama]

Hey guys, I was just wondering what the prerequisites of this course are. I used to know some programming in C++ but I have forgotten most of it. Currently, I am trying to learn how to make animations in Manim. Do you think I have sufficient background for making this course worthwhile? If not, what should I study before taking this course? Any help would be great. Thank you:)

[@Pluvo2for1]

I'd it interests you I'd suggest you do it. Each time you don't understand something stop this video and go off and find more detail from elsewhere, and then come back. Also make sure you do your own examples, and lastly test yourself by pretending to explain each topic to an imaginary friend.

[@unnamedchannelowouwu]

I'm starting my cs studies the next year, I know nothing about the topic but just maths and python, should I take this course now or wait until the middle of the entire five years of study for that?

[@chococandy8009]

Probably the only semester that I would like to attend without bunking a single lecture ;) It was fun.

[@THEMithrandir09]

Something that's conceptually quite interesting but is hardly ever explained, is that the shell is just a ReadEvaluatePrintLoop(REPL) for the programming language called bash(sh, zsh,...), much like the Python REPL. So if you use the commandline(or the GUI for that matter, since clicks just call functions for you), you are writing and executing a program at the same time(but not saving it for repeated use).

[@TheEnde124]

You can also use cat and > to write an iso file to a usb device cat some-os.iso > /dev/sdx

[@fhajji]

You most certainly can do this, but is is more efficient and faster to use 'dd', because it can copy in fixed-size sectors (the bs= parameter), which is much better for usb flash drives... provided you pick the right block size!

[@amateruss]

I'm using windows powershell and some of the commands that he uses does not work on mine just like echo $PATH. Do I have to do some tweaking in order for them to work on mine or I am missing something important?

[@MissingSemester]

PowerShell is quite different from POSIX-compatible shells like the one taught in this video. If you want to learn PowerShell, this isn't the right resource. If you want to install a POSIX-compatible shell on your machine, you can try using Windows Subsystem for Linux (docs.microsoft.com/en-us/windows/wsl/install-win10).

[@muluman88]

Powershell has all environment variables below $env, so $env:path for that particular one.

[@angelsalinas9697]

can someone help me, when I do, cd /sys in my mac terminal it says no file or directory found.

[@EricJohn-h2c]

thanks for the open resources of mit

[@FrederizEguren]

He is very eloquent.

[@jamoinmoin]

wow so many small useful things that actually boost productivity, great lecture

[@KonstantinDorichev]

I remembered the basics and did learn a few commands I didn't know. Thanks!

[@anupkodlekere8604]

Is that Jon Gjenset?

[@joanperezlozano7405]

Hello everyone! I have been trying to use the "ls (dash)(dash)help" command as it was written by the professor, but I get some strange error (goes like this: ls: illegal option -- - usage: ls [-@ABCFGHLOPRSTUWabcdefghiklmnopqrstuwx1%] [file ...]) I have dome some research and apparently the "man ls" command could be another possible way of checking out documentation. My question is why the "ls --help" command did not workout in my case? is it because of the version of my OS? P.S. Im using macOS (Catalina 10.15.5 ) Terminal. Thanks for the great content Missing Semester!!!

[@heisvi9317]

Maybe you know this now, but apparently (after a quick google search since I don't have a Mac) they switch to zsh in place of bash, so that's probably why.

[@hulk94smash]

WOWOWOWOWOWOW THIS IS GOLDDD!!! 🔥💯 wish I knew this year's ago 😭

[@warshipwarriors]

Well I am using Debian but the xdg command is not found. Apparently, the tutor said it's available in Linux systems. Main worry is get other similar not found commands.

[@mugen1305]

I'm not able to run some of the commands like pipe, ls -l etc..on windows powershell. Do I need Linux?

[@AK47_414]

Is there a bash command cheat sheet anywhere I can use? The ones I googled where not very concise or helpful. A good 1 page cheat sheet would be very useful

[@iduran]

Nice terminal setup. I already checked the instructor's dotfiles but couldn't find which font he is using. Any idea what font that is?

[@yuexiao4739]

Love this course! Really helped me on my work.

[@zacharycarbon4312]

@43:00 the problem was the usage of single quotes. bash treats single quotes as string literals. so you were basically asking find to search for the string \*brightness\*. also, the '-iname' flag is better suited for regex search strings.

[@venusumanthpotru9535]

This is super helpful 👍. Thanks a lot for uploading it to KZbin.

[@mubintirsaiwala7141]

I just can't thank you enough. Great content.

[@neo22501]

which distribution is he using?

[@knowledgeseeker2452]

Is this course beginner friendly?