1
00:00:00,480 --> 00:00:02,480
Okay, can everyone hear me okay?

2
00:00:03,720 --> 00:00:06,160
Okay, so welcome back.

3
00:00:06,160 --> 00:00:10,320
I'm gonna address a couple of items
in kind of the administratrivia.

4
00:00:10,640 --> 00:00:13,080
With the end of the first week,

5
00:00:13,179 --> 00:00:16,349
we sent an email, noticing you that

6
00:00:16,600 --> 00:00:20,219
we have uploaded the videos for the first
week, so you can now find them online.

7
00:00:20,470 --> 00:00:26,670
They have all the screen recordings for the things
that we were doing, so you can go back to them.

8
00:00:26,830 --> 00:00:31,439
Look if you're were confused about if
we did something quick and, again,

9
00:00:31,440 --> 00:00:37,560
feel free to ask us any questions if anything in the
lecture notes is not clear. We also sent you a

10
00:00:37,880 --> 00:00:42,360
survey so you can give us feedback
about what was not clear,

11
00:00:42,360 --> 00:00:46,280
what items you would want a
more thorough explanation or

12
00:00:47,110 --> 00:00:51,749
just any other item, if you're finding
the exercises too hard, too easy,

13
00:00:52,239 --> 00:00:55,288
go into that URL and we'll really

14
00:00:55,960 --> 00:01:00,040
appreciate getting that feedback, because
that will make the course better

15
00:01:00,480 --> 00:01:03,800
for the remaining lectures and for
future iterations of the course.

16
00:01:05,080 --> 00:01:07,080
With that out of the way

17
00:01:07,080 --> 00:01:10,840
Oh, and we're gonna try to upload the
videos in a more timely manner.

18
00:01:11,200 --> 00:01:16,040
We don't want to kind of wait until the end of
the week for that. So keep tuned for that.

19
00:01:18,760 --> 00:01:19,840
That out of the way,

20
00:01:19,920 --> 00:01:20,800
now I'm gonna

21
00:01:21,120 --> 00:01:24,960
This lecture's called command-line
environment and we're

22
00:01:25,160 --> 00:01:28,440
going to cover a few different topics. So the

23
00:01:28,990 --> 00:01:30,990
main topics we're gonna

24
00:01:32,040 --> 00:01:34,520
cover, so you can keep track,

25
00:01:34,680 --> 00:01:36,400
it's probably better here,

26
00:01:36,400 --> 00:01:37,720
keep track of what I'm talking.

27
00:01:37,920 --> 00:01:41,560
The first is gonna be job control.

28
00:01:42,040 --> 00:01:44,280
The second one is going to be

29
00:01:44,600 --> 00:01:46,600
terminal multiplexers.

30
00:01:51,720 --> 00:01:57,360
Then I'm going to explain what dotfiles
are and how to configure your shell.

31
00:01:57,360 --> 00:02:03,240
And lastly, how to efficiently work with
remote machines. So if things are not

32
00:02:05,110 --> 00:02:07,589
fully clear, kind of keep the structure.

33
00:02:08,200 --> 00:02:12,320
They all kind of interact in some
way, of how you use your terminal,

34
00:02:12,880 --> 00:02:17,280
but they are somewhat separate
topics, so keep that in mind.

35
00:02:17,600 --> 00:02:23,800
So let's go with job control. So far we have
been using the shell in a very, kind of

36
00:02:24,800 --> 00:02:27,720
mono-command way. Like, you
execute a command and then

37
00:02:27,840 --> 00:02:31,800
the command executes, then you get some output,
and that's all about what you can do.

38
00:02:32,200 --> 00:02:36,520
And if you want to run several
things, it's not clear

39
00:02:36,540 --> 00:02:41,099
how you will do it. Or if you want to stop
the execution of a program, it's again,

40
00:02:41,099 --> 00:02:43,768
like how do I know how to stop a program?

41
00:02:44,650 --> 00:02:47,940
Let's showcase this with a command called sleep.

42
00:02:48,160 --> 00:02:50,320
Sleep is a command that takes an argument,

43
00:02:50,320 --> 00:02:54,360
and that argument is going to be an
integer number, and it will sleep.

44
00:02:54,360 --> 00:02:58,440
It will just kind of be there, on the
background, for that many seconds.

45
00:02:58,440 --> 00:03:03,539
So if we do something like sleep 20, this process
is gonna be sleeping for 20 seconds.

46
00:03:03,539 --> 00:03:07,720
But we don't want to wait 20 seconds
for the command to complete.

47
00:03:08,040 --> 00:03:10,800
So what we can do is type "Ctrl+C".

48
00:03:10,840 --> 00:03:12,580
By typing "Ctrl+C"

49
00:03:12,580 --> 00:03:17,840
We can see that, here, the terminal let us know,

50
00:03:18,880 --> 00:03:22,840
and it's part of the syntax that we covered
in the editors / Vim lecture,

51
00:03:23,000 --> 00:03:27,200
that we typed "Ctrl+C" and it stopped
the execution of the process.

52
00:03:27,640 --> 00:03:29,640
What is actually going on here

53
00:03:29,880 --> 00:03:34,840
is that this is using a UNIX communication
mechanism called signals.

54
00:03:35,120 --> 00:03:37,360
When we type "Ctrl+C",

55
00:03:37,800 --> 00:03:42,080
what the terminal did for us,
or the shell did for us,

56
00:03:42,160 --> 00:03:45,960
is send a signal called SIGINT,

57
00:03:45,960 --> 00:03:51,320
that stands for SIGnal INTerrupt, that
tells the program to stop itself.

58
00:03:51,680 --> 00:03:57,520
And there are many, many, many signals
of this kind. If you do man signal,

59
00:03:58,880 --> 00:04:05,060
and just go down a little bit,
here you have a list of them.

60
00:04:05,060 --> 00:04:07,040
They all have number identifiers,

61
00:04:07,520 --> 00:04:10,640
they have kind of a short name
and you can find a description.

62
00:04:10,960 --> 00:04:16,400
So for example, the one I have just
described is here, number 2, SIGINT.

63
00:04:16,520 --> 00:04:22,200
This is the signal that a terminal will send to a
program when it wants to interrupt its execution.

64
00:04:22,520 --> 00:04:25,840
A few more to be familiar with

65
00:04:26,460 --> 00:04:28,530
is SIGQUIT, this is

66
00:04:29,229 --> 00:04:34,409
again, if you work from a terminal and you
want to quit the execution of a program.

67
00:04:34,409 --> 00:04:37,720
For most programs it will do the same thing,

68
00:04:37,720 --> 00:04:41,120
but we're gonna showcase now a program
which will be different,

69
00:04:41,440 --> 00:04:43,760
and this is the signal that will be sent.

70
00:04:44,680 --> 00:04:49,229
It can be confusing sometimes. Looking at
these signals, for example, the SIGTERM is

71
00:04:50,080 --> 00:04:54,100
for most cases equivalent to SIGINT and SIGQUIT

72
00:04:54,480 --> 00:04:58,380
but it's just when it's not
sent through a terminal.

73
00:04:59,680 --> 00:05:01,680
A few more that we're gonna

74
00:05:01,900 --> 00:05:06,209
cover is SIGHUP, it's when there's
like a hang-up in the terminal.

75
00:05:06,210 --> 00:05:10,199
So for example, when you are in your
terminal, if you close your terminal

76
00:05:10,199 --> 00:05:13,348
and there are still things
running in the terminal,

77
00:05:13,480 --> 00:05:17,000
that's the signal that the program is gonna send

78
00:05:17,000 --> 00:05:19,960
to all the processes to tell
that they should close,

79
00:05:19,960 --> 00:05:25,080
like there was a hang-up in the
command line communication

80
00:05:25,080 --> 00:05:26,800
and they should close now.

81
00:05:28,400 --> 00:05:34,260
Signals can do more things than just stopping, interrupting
programs and asking them to finish.

82
00:05:34,260 --> 00:05:36,840
You can for example use the

83
00:05:37,520 --> 00:05:43,840
SIGSTOP to pause the execution of the
program, and then you can use the

84
00:05:44,480 --> 00:05:50,160
SIGCONT command for continuing, to continue the execution
of the program at a point later in time.

85
00:05:51,160 --> 00:05:55,440
Since all of this might be slightly too
abstract, let's see a few examples.

86
00:05:58,040 --> 00:06:00,560
First, let's showcase a

87
00:06:01,960 --> 00:06:06,240
Python program. I'm going to very
quickly go through the program.

88
00:06:06,440 --> 00:06:08,360
This is a Python program,

89
00:06:08,720 --> 00:06:10,760
that like most python programs,

90
00:06:11,520 --> 00:06:13,960
is importing this signal library and

91
00:06:14,960 --> 00:06:20,400
is defining this handler here.
And this handler is writing,

92
00:06:20,440 --> 00:06:23,040
"Oh, I got a SIGINT, but
I'm not gonna stop here".

93
00:06:23,480 --> 00:06:24,960
And after that,

94
00:06:24,960 --> 00:06:30,720
we tell Python that we want this program,
when it gets a SIGINT, to stop.

95
00:06:31,120 --> 00:06:34,880
The rest of the program is a very silly program
that is just going to be printing numbers.

96
00:06:35,060 --> 00:06:37,540
So let's see this in action.

97
00:06:37,560 --> 00:06:39,560
We do Python SIGINT.

98
00:06:39,880 --> 00:06:44,970
And it's counting. We try doing
"Ctrl+C", this sends a SIGINT,

99
00:06:44,970 --> 00:06:50,000
but the program didn't actually stop. This
is because we have a way in the program of

100
00:06:50,400 --> 00:06:54,600
dealing with this exception,
and we didn't want to exit.

101
00:06:54,760 --> 00:06:57,600
If we send a SIGQUIT, which is done through

102
00:06:57,800 --> 00:07:03,680
"Ctrl+\", here, we can see that since the program
doesn't have a way of dealing with SIGQUIT,

103
00:07:03,730 --> 00:07:06,269
it does the default operation, which is

104
00:07:06,820 --> 00:07:08,800
terminate the program.

105
00:07:09,080 --> 00:07:11,460
And you could use this, for example,

106
00:07:11,880 --> 00:07:15,880
if someone Ctrl+C's your program, and your
program is supposed to do something,

107
00:07:16,040 --> 00:07:19,320
like you maybe want to save the intermediate
state of your program

108
00:07:19,320 --> 00:07:21,520
to a file, so you can recover it for later.

109
00:07:21,600 --> 00:07:25,640
This is how you could write a handler like this.

110
00:07:29,520 --> 00:07:30,720
Can you repeat the question?

111
00:07:30,880 --> 00:07:32,280
What did you type right now, when it stopped?

112
00:07:32,480 --> 00:07:34,480
So I...

113
00:07:34,630 --> 00:07:38,880
So what I typed is, I type
"Ctrl+C" to try to stop it

114
00:07:38,880 --> 00:07:42,869
but it didn't, because SIGINT is captured
by the program. Then I type

115
00:07:43,120 --> 00:07:48,040
"Ctrl+\", which sends a SIGQUIT,
which is a different signal,

116
00:07:49,000 --> 00:07:51,720
and this signal is not captured by the program.

117
00:07:52,090 --> 00:07:54,869
It's also worth mentioning
that there is a couple of

118
00:07:54,970 --> 00:07:59,970
signals that cannot be captured by software.
There is a couple of signals

119
00:08:00,820 --> 00:08:02,820
like SIGKILL

120
00:08:03,940 --> 00:08:06,600
that cannot be captured. Like that, it will

121
00:08:06,660 --> 00:08:09,300
terminate the execution of the
process, no matter what.

122
00:08:09,300 --> 00:08:12,000
And it can be sometimes harmful.
You do not want to be using it by

123
00:08:12,000 --> 00:08:16,460
default, because this can leave for example an
orphan child, orphaned children processes.

124
00:08:16,470 --> 00:08:20,940
Like if a process has other small children
processes that it started, and you

125
00:08:21,400 --> 00:08:25,470
SIGKILL it, all of those will
keep running in there,

126
00:08:25,760 --> 00:08:30,800
but they won't have a parent, and you can maybe
have a really weird behavior going on.

127
00:08:32,040 --> 00:08:35,680
What signal is given to the
program if we log off?

128
00:08:35,800 --> 00:08:37,440
If you log off?

129
00:08:37,920 --> 00:08:41,920
That would be... so for example, if you're in an
SSH connection and you close the connection,

130
00:08:41,920 --> 00:08:45,600
that is the hang-up signal,

131
00:08:45,600 --> 00:08:51,200
SIGHUP, which I'm gonna cover in an example.
So this is what would be sent up.

132
00:08:51,560 --> 00:08:56,360
And you could write for example, if you want
the process to keep working even if you close

133
00:08:56,960 --> 00:09:02,560
that, you can write a wrapper around
that to ignore that signal.

134
00:09:04,720 --> 00:09:09,760
Let's display what we could do
with the stop and continue.

135
00:09:09,980 --> 00:09:16,389
So, for example, we can start a really long process.
Let's sleep a thousand, we're gonna take forever.

136
00:09:16,960 --> 00:09:18,920
We can control-c,

137
00:09:18,920 --> 00:09:20,360
"Ctrl+Z", sorry,

138
00:09:20,360 --> 00:09:25,280
and if we do "Ctrl+Z" we can see that the
terminal is saying "it's suspended".

139
00:09:25,400 --> 00:09:31,520
What this actually meant is that this process
was sent a SIGSTOP signal and now is

140
00:09:31,900 --> 00:09:36,900
still there, you could continue its execution, but right
now it's completely stopped and in the background

141
00:09:38,580 --> 00:09:41,720
and we can launch a different program.

142
00:09:41,720 --> 00:09:43,680
When we try to run this program,

143
00:09:43,680 --> 00:09:46,620
please notice that I have included
an "&" at the end.

144
00:09:46,820 --> 00:09:52,380
This tells bash that I want this program
to start running in the background.

145
00:09:52,560 --> 00:09:55,660
This is kind of related to all these

146
00:09:55,660 --> 00:09:59,720
concepts of running programs in
the shell, but backgrounded.

147
00:10:00,350 --> 00:10:04,359
And what is gonna happen is
the program is gonna start

148
00:10:04,720 --> 00:10:07,580
but it's not gonna take over my prompt.

149
00:10:07,580 --> 00:10:11,540
If I just ran this command without
this, I could not do anything.

150
00:10:11,540 --> 00:10:15,820
I would have no access to the prompt
until the command either finished

151
00:10:16,060 --> 00:10:19,380
or I ended it abruptly. But if I do this,

152
00:10:19,520 --> 00:10:23,080
it's saying "there's a new
process which is this".

153
00:10:23,080 --> 00:10:25,180
This is the process identifying number,

154
00:10:25,180 --> 00:10:26,940
we can ignore this for now.

155
00:10:27,800 --> 00:10:32,919
If I type the command "jobs", I get the
output that I have a suspended job

156
00:10:32,920 --> 00:10:35,800
that is the "sleep 1000" job.

157
00:10:36,040 --> 00:10:38,100
And then I have another running job,

158
00:10:38,120 --> 00:10:42,200
which is this "NOHUP sleep 2000".

159
00:10:42,640 --> 00:10:45,660
Say I want to continue the first job.

160
00:10:45,660 --> 00:10:48,520
The first job is suspended,
it's not executing anymore.

161
00:10:48,640 --> 00:10:52,600
I can continue that doing "BG %1"

162
00:10:53,870 --> 00:10:58,359
That "%" is referring to the fact that
I want to refer to this specific

163
00:11:00,280 --> 00:11:04,280
process. And now, if I do that
and I look at the jobs,

164
00:11:04,300 --> 00:11:06,460
now this job is running again. Now

165
00:11:06,460 --> 00:11:08,940
both of them are running.

166
00:11:09,300 --> 00:11:13,820
If I wanted to stop these all,
I can use the kill command.

167
00:11:14,040 --> 00:11:16,060
The kill command

168
00:11:16,220 --> 00:11:18,620
is for killing jobs,

169
00:11:19,180 --> 00:11:22,080
which is just stopping them, intuitively,

170
00:11:22,120 --> 00:11:23,760
but actually it's really useful.

171
00:11:23,860 --> 00:11:28,200
The kill command just allows you
to send any sort of Unix signal.

172
00:11:28,360 --> 00:11:32,220
So here for example, instead
of killing it completely,

173
00:11:32,220 --> 00:11:34,640
we just send a stop signal.

174
00:11:34,640 --> 00:11:39,160
Here I'm gonna send a stop signal, which
is gonna pause the process again.

175
00:11:39,160 --> 00:11:41,280
I still have to include the identifier,

176
00:11:41,600 --> 00:11:46,480
because without the identifier the shell wouldn't know
whether to stop the first one or the second one.

177
00:11:47,480 --> 00:11:52,480
Now it's said this has been suspended,
because there was a signal sent.

178
00:11:52,620 --> 00:11:57,360
If I do "jobs", again, we can see
that the second one is running

179
00:11:57,460 --> 00:12:00,740
and the first one has been stopped.

180
00:12:01,420 --> 00:12:04,300
Going back to one of the questions,

181
00:12:04,300 --> 00:12:06,980
what happens when you close
the cell, for example,

182
00:12:06,980 --> 00:12:12,860
and why sometimes people will say that
you should use this NOHUP command

183
00:12:12,860 --> 00:12:15,960
before your run jobs in a remote session.

184
00:12:16,220 --> 00:12:23,120
This is because if we try to send
a hung up command to the first job

185
00:12:23,560 --> 00:12:27,820
it's gonna, in a similar fashion
as the other signals,

186
00:12:27,820 --> 00:12:32,280
it's gonna hang it up and that's
gonna terminate the job.

187
00:12:32,800 --> 00:12:35,960
And the first job isn't there anymore

188
00:12:36,320 --> 00:12:39,140
whereas we have still the second job running.

189
00:12:39,400 --> 00:12:42,920
However, if we try to send the
signal to the second job

190
00:12:42,920 --> 00:12:46,060
what will happen if we close
our terminal right now

191
00:12:47,040 --> 00:12:48,660
is it's still running.

192
00:12:48,660 --> 00:12:52,480
Like NOHUP, what it's doing
is kind of encapsulating

193
00:12:52,480 --> 00:12:54,480
whatever command you're executing and

194
00:12:54,740 --> 00:12:58,720
ignoring wherever you get a hang up signal,

195
00:12:58,900 --> 00:13:03,680
and just ignoring that so it can keep running.

196
00:13:05,060 --> 00:13:08,500
And if we send the "kill"
signal to the second job,

197
00:13:08,500 --> 00:13:12,820
that one can't be ignored and that
will kill the job, no matter what.

198
00:13:13,280 --> 00:13:15,780
And we don't have any jobs anymore.

199
00:13:17,000 --> 00:13:22,540
That kind of completes the
section on job control.

200
00:13:22,740 --> 00:13:27,100
Any questions so far? Anything
that wasn't fully clear?

201
00:13:29,040 --> 00:13:30,400
What does BG do?

202
00:13:30,960 --> 00:13:31,800
So BG...

203
00:13:31,800 --> 00:13:36,860
There are like two commands. Whenever you
have a command that has been backgrounded

204
00:13:37,200 --> 00:13:41,820
and is stopped you can use
BG (short for background)

205
00:13:41,820 --> 00:13:44,180
to continue that process running
on the background.

206
00:13:44,440 --> 00:13:47,400
That's equivalent of just kind of sending it

207
00:13:47,680 --> 00:13:50,820
a continue signal, so it keeps running.

208
00:13:50,820 --> 00:13:54,820
And then there's another one which
is called FG, if you want to

209
00:13:54,860 --> 00:13:59,580
recover it to the foreground and you want
to reattach your standard output.

210
00:14:04,760 --> 00:14:06,760
Okay, good.

211
00:14:07,120 --> 00:14:11,420
Jobs are useful and in general, I
think knowing about signals can be

212
00:14:11,420 --> 00:14:14,360
really beneficial when dealing
with some part of Unix

213
00:14:14,360 --> 00:14:19,420
but most of the time what you actually want
to do is something along the lines of

214
00:14:19,670 --> 00:14:24,099
having your editor in one side and then
the program in another, and maybe

215
00:14:24,720 --> 00:14:28,280
monitoring what the resource
consumption is in our tab.

216
00:14:28,680 --> 00:14:33,640
We could achieve this using probably
what you have seen a lot of the time,

217
00:14:33,640 --> 00:14:35,200
which is just opening more windows.

218
00:14:35,200 --> 00:14:37,200
We can keep opening terminal windows.

219
00:14:37,320 --> 00:14:41,280
But the fact is there are kind of more
convenient solutions to this and

220
00:14:41,280 --> 00:14:43,800
this is what a terminal multiplexer does.

221
00:14:44,080 --> 00:14:48,520
A terminal multiplexer like tmux

222
00:14:48,840 --> 00:14:52,160
will let you create different workspaces
that you can work in,

223
00:14:52,640 --> 00:14:54,280
and quickly kind of,

224
00:14:54,280 --> 00:14:56,960
this has a huge variety of functionality,

225
00:14:57,320 --> 00:15:02,760
It will let you rearrange the environment and
it will let you have different sessions.

226
00:15:03,400 --> 00:15:05,400
There's another more...

227
00:15:05,600 --> 00:15:07,640
older command, which is called "screen",

228
00:15:07,640 --> 00:15:09,360
that might be more readily available.

229
00:15:09,360 --> 00:15:12,200
But I think the concept kind
of extrapolates to both.

230
00:15:12,600 --> 00:15:15,400
We recommend tmux, that you go and learn it.

231
00:15:15,400 --> 00:15:17,480
And in fact, we have exercises on it.

232
00:15:17,480 --> 00:15:20,240
I'm gonna showcase a different
scenario right now.

233
00:15:20,320 --> 00:15:22,000
So whenever I talked...

234
00:15:22,320 --> 00:15:24,880
Oh, let me make a quick note.

235
00:15:25,200 --> 00:15:28,800
There are kind of three core concepts
in tmux, that I'm gonna go through and

236
00:15:30,110 --> 00:15:33,130
the main idea is that there are what is called

237
00:15:35,180 --> 00:15:37,180
"sessions".

238
00:15:37,760 --> 00:15:40,510
Sessions have "windows" and

239
00:15:42,019 --> 00:15:44,019
windows have "panes".

240
00:15:45,709 --> 00:15:49,539
It's gonna be kind of useful to
keep this hierarchy in mind.

241
00:15:50,760 --> 00:15:57,280
You can pretty much equate "windows" to what
"tabs" are in other editors and others,

242
00:15:57,280 --> 00:16:00,720
like for example your web browser.

243
00:16:01,280 --> 00:16:06,440
I'm gonna go through the features, mainly
what you can do at the different levels.

244
00:16:07,000 --> 00:16:10,480
So first, when we do tmux, that starts a session.

245
00:16:11,360 --> 00:16:14,960
And here right now it seems like nothing changed

246
00:16:14,960 --> 00:16:20,360
but what's happening right now is we're within a shell
that is different from the one we started before.

247
00:16:20,640 --> 00:16:24,840
So in our shell we started
a process, that is tmux

248
00:16:24,840 --> 00:16:28,840
and that tmux started a different process,
which is the shell we're currently in.

249
00:16:28,980 --> 00:16:30,400
And the nice thing about this is that

250
00:16:30,580 --> 00:16:34,740
that tmux process is separate from
the original shell process.

251
00:16:34,860 --> 00:16:36,860
So

252
00:16:40,580 --> 00:16:44,460
here, we can do things.

253
00:16:44,480 --> 00:16:48,600
We can do "ls -la", for example, to
tell us what is going on in here.

254
00:16:48,920 --> 00:16:53,960
And then we can start running our program,
and it will start running in there

255
00:16:54,160 --> 00:16:57,880
and we can do "Ctrl+A d", for example, to detach

256
00:17:12,760 --> 00:17:15,960
to detach from the session.

257
00:17:16,140 --> 00:17:19,120
And if we do "tmux a"

258
00:17:19,160 --> 00:17:21,560
that's gonna reattach us to the session.

259
00:17:21,560 --> 00:17:22,300
So the process,

260
00:17:22,300 --> 00:17:25,180
we abandon the process counting numbers.

261
00:17:25,180 --> 00:17:28,300
This really silly Python program
that was just counting numbers,

262
00:17:28,340 --> 00:17:30,160
we left it running there.

263
00:17:30,200 --> 00:17:31,720
And if we tmux...

264
00:17:31,720 --> 00:17:33,760
Hey, the process is still running there.

265
00:17:33,780 --> 00:17:37,820
And we could close this entire
terminal and open a new one and

266
00:17:37,880 --> 00:17:41,860
we could still reattach because this
tmux session is still running.

267
00:17:43,340 --> 00:17:45,340
Again, we can...

268
00:17:46,640 --> 00:17:48,640
Before I go any further.

269
00:17:48,920 --> 00:17:53,740
Pretty much... Unlike Vim, where
you have this notion of modes,

270
00:17:53,960 --> 00:17:58,180
tmux will work in a more emacsy way, which is

271
00:17:58,180 --> 00:18:04,140
every command, pretty much every command in tmux,

272
00:18:04,220 --> 00:18:06,020
you could enter it through the...

273
00:18:06,020 --> 00:18:08,160
it has a command line, that we could use.

274
00:18:08,240 --> 00:18:11,320
But I recommend you to get familiar
with the key bindings.

275
00:18:11,880 --> 00:18:15,080
It can be somehow non intuitive at first,

276
00:18:15,300 --> 00:18:17,880
but once you get used to them...

277
00:18:22,140 --> 00:18:23,020
"Ctrl+C", yeah

278
00:18:24,440 --> 00:18:30,760
When you get familiar with them, you will be much faster
just using the key bindings than using the commands.

279
00:18:31,280 --> 00:18:35,980
One note about the key bindings: all the
key bindings have a form that is like

280
00:18:36,140 --> 00:18:39,840
you type a prefix and then some key.

281
00:18:40,060 --> 00:18:44,000
So for example, to detach we
do "Ctrl+A" and then "D".

282
00:18:44,160 --> 00:18:50,140
This means you press "Ctrl+A" first, you release
that, and then press "D" to detach.

283
00:18:50,380 --> 00:18:54,200
On default tmux, the prefix is "Ctrl+B",

284
00:18:54,200 --> 00:18:58,780
but you will find that most people
will have this remapped to "Ctrl+A"

285
00:18:58,780 --> 00:19:02,680
because it's a much more ergonomic
type on the keyboard.

286
00:19:02,700 --> 00:19:06,420
You can find more about how to do these
things in one of the exercises,

287
00:19:06,960 --> 00:19:12,780
where we link you to the basics and how to do some
kind of quality of life modifications to tmux.

288
00:19:13,380 --> 00:19:16,720
Going back to the concept of sessions,

289
00:19:16,960 --> 00:19:22,120
we can create a new session just
doing something like tmux new

290
00:19:22,320 --> 00:19:24,540
and we can give sessions names.

291
00:19:24,760 --> 00:19:27,220
So we can do like "tmux new -t foobar"

292
00:19:27,220 --> 00:19:30,900
and this is a completely different
session, that we have started.

293
00:19:32,240 --> 00:19:36,360
We can work here, we can detach from it.

294
00:19:36,360 --> 00:19:40,000
"tmux ls" will tell us that we
have two different sessions:

295
00:19:40,000 --> 00:19:43,460
the first one is named "0", because
I didn't give it a name,

296
00:19:43,500 --> 00:19:45,820
and the second one is called "foobar".

297
00:19:46,580 --> 00:19:51,020
I can attach the foobar session

298
00:19:51,020 --> 00:19:53,700
and I can end it.

299
00:19:54,680 --> 00:19:56,340
And it's really nice because

300
00:19:56,340 --> 00:20:00,139
having this you can kind of work
in completely different projects.

301
00:20:00,140 --> 00:20:04,340
For example, having two different
tmux sessions and different

302
00:20:04,480 --> 00:20:08,440
editor sessions, different processes running...

303
00:20:10,160 --> 00:20:15,100
When you are within a session, we
start with the concept of windows.

304
00:20:15,100 --> 00:20:21,160
Here we have a single window, but we
can use "Ctrl+A c" (for "create")

305
00:20:21,160 --> 00:20:23,720
to open a new window.

306
00:20:24,000 --> 00:20:26,340
And here nothing is executing.

307
00:20:26,380 --> 00:20:29,420
What it's doing is, tmux has
opened a new shell for us

308
00:20:30,360 --> 00:20:34,840
and we can start running another
one of these programs here.

309
00:20:35,460 --> 00:20:42,460
And to quickly jump between the tabs,
we can do "Ctrl+A" and "previous",

310
00:20:42,460 --> 00:20:44,520
"p" for "previous",

311
00:20:45,220 --> 00:20:48,020
and that will go up to the previous window.

312
00:20:48,020 --> 00:20:50,920
"Ctrl+A" "next", to go to the next window.

313
00:20:51,260 --> 00:20:56,060
You can also use the numbers. So if we
start opening a lot of these tabs,

314
00:20:56,200 --> 00:21:00,160
we could use "Ctrl+A 1", to
specifically jump to the

315
00:21:00,240 --> 00:21:04,400
to the window that is number "1".

316
00:21:04,780 --> 00:21:08,620
And, lastly, it's also pretty
useful to know sometimes

317
00:21:08,660 --> 00:21:10,400
that you can rename them.

318
00:21:10,400 --> 00:21:13,380
For example here I'm executing
this Python process,

319
00:21:13,580 --> 00:21:16,800
but that might not be really
informative and I want...

320
00:21:16,880 --> 00:21:21,160
I maybe want to have something like
execution or something like that and

321
00:21:21,740 --> 00:21:26,840
that will rename the name of that window so
you can have this really neatly organized.

322
00:21:27,080 --> 00:21:33,500
This still doesn't solve the need when you want to
have two things at the same time in your terminal,

323
00:21:33,680 --> 00:21:35,740
like in the same display.

324
00:21:35,740 --> 00:21:38,320
This is what panes are for. Right now, here

325
00:21:38,420 --> 00:21:40,420
we have a window with a single pane

326
00:21:40,420 --> 00:21:43,540
(all the windows that we have opened
so far have a single pane).

327
00:21:43,640 --> 00:21:50,800
But if we do 'Ctrl+A "'

328
00:21:51,040 --> 00:21:56,540
this will split the current display
into two different panes.

329
00:21:56,540 --> 00:22:01,400
So, you see, the one we open below is a different
shell from the one we have above,

330
00:22:01,640 --> 00:22:05,440
and we can run any process that we want here.

331
00:22:05,620 --> 00:22:09,900
We can keep splitting this, if we do "Ctrl+A %"

332
00:22:10,080 --> 00:22:15,000
that will split vertically. And you can kind of

333
00:22:15,000 --> 00:22:18,220
rearrange these tabs using a
lot of different commands.

334
00:22:18,220 --> 00:22:22,620
One that I find very useful, when you are
starting and it's kind of frustrating,

335
00:22:23,540 --> 00:22:26,000
rearranging them.

336
00:22:26,160 --> 00:22:30,160
Before I explain that, to move
through these panes, which is

337
00:22:30,300 --> 00:22:32,280
something you want to be doing all the time

338
00:22:32,460 --> 00:22:37,060
You just do "Ctrl+A" and the arrow
keys, and that will let you quickly

339
00:22:37,460 --> 00:22:43,960
navigate through the different
windows, and execute again...

340
00:22:44,340 --> 00:22:46,300
I'm doing a lot of "ls -a"

341
00:22:47,340 --> 00:22:52,780
I can do "HTOP", that we'll explain in
the debugging and profiling lecture.

342
00:22:53,540 --> 00:22:55,920
And we can just navigate through them, again

343
00:22:55,920 --> 00:22:59,040
like to rearrange there's
another slew of commands,

344
00:22:59,080 --> 00:23:01,080
you will go through some in the Exercises

345
00:23:02,400 --> 00:23:07,160
"Ctrl+A" space is pretty neat, because it
will kind of equispace the current ones

346
00:23:07,160 --> 00:23:10,260
and let you through different layouts.

347
00:23:11,480 --> 00:23:14,260
Some of them are too small for my current

348
00:23:14,840 --> 00:23:19,220
terminal config, but that covers,
I think, most of it.

349
00:23:19,440 --> 00:23:21,440
Oh, there's also,

350
00:23:22,660 --> 00:23:29,200
here, for example, this Vim execution
that we have started,

351
00:23:29,200 --> 00:23:33,380
is too small for what the current tmux pane is.

352
00:23:33,720 --> 00:23:38,240
So one of the things that really is
much more convenient to do in tmux,

353
00:23:39,180 --> 00:23:42,500
in contrast to having multiple
terminal windows, is that

354
00:23:42,560 --> 00:23:48,400
you can zoom into this, you can ask
by doing "Ctrl+A z", for "zoom".

355
00:23:48,400 --> 00:23:52,960
It will expand the pane to
take over all the space,

356
00:23:52,960 --> 00:23:56,660
and then "Ctrl+A z", again will go back to it.

357
00:24:02,760 --> 00:24:08,080
Any questions for terminal multiplexers,
or like, tmux concretely?

358
00:24:14,140 --> 00:24:16,780
Is it running all the same thing?

359
00:24:18,680 --> 00:24:22,700
Like, is there any difference in execution
between running it in different windows?

360
00:24:24,880 --> 00:24:28,640
Is it really just doing it all the
same, so that you can see it?

361
00:24:28,800 --> 00:24:34,900
Yeah, it wouldn't be any different from having
two terminal windows open in your computer.

362
00:24:34,920 --> 00:24:39,220
Like both of them are gonna be running.
Of course, when it gets to the CPU,

363
00:24:39,220 --> 00:24:41,400
this is gonna be multiplexed again.

364
00:24:41,460 --> 00:24:44,400
Like there's like a timesharing
mechanism going there

365
00:24:44,480 --> 00:24:45,920
but there's no difference.

366
00:24:46,040 --> 00:24:52,260
tmux is just making this much more convenient
to use by giving you this visual layout

367
00:24:52,560 --> 00:24:55,020
that you can quickly manipulate through.

368
00:24:55,020 --> 00:24:59,860
And one of the main advantages will come
when we reach the remote machines

369
00:24:59,860 --> 00:25:05,300
because you can leave one of these, we can
detach from one of these tmux systems,

370
00:25:05,300 --> 00:25:09,120
close the connection and even
if we close the connection and

371
00:25:09,120 --> 00:25:11,640
and the terminal is gonna send a hang-up signal,

372
00:25:11,680 --> 00:25:15,420
that's not gonna close all the
tmux's that have been started.

373
00:25:17,110 --> 00:25:19,110
Any other questions?

374
00:25:23,620 --> 00:25:27,980
Let me disable the key-caster.

375
00:25:33,580 --> 00:25:38,040
So now we're gonna move into the topic
of dotfiles and, in general,

376
00:25:38,040 --> 00:25:42,460
how to kind of configure your shell
to do the things you want to do

377
00:25:42,460 --> 00:25:45,580
and mainly how to do them quicker
and in a more convenient way.

378
00:25:46,360 --> 00:25:49,260
I'm gonna motivate this using aliases first.

379
00:25:49,380 --> 00:25:51,060
So what an alias is,

380
00:25:51,060 --> 00:25:54,260
is that by now, you might be
starting to do something like

381
00:25:54,920 --> 00:26:01,680
a lot of the time, I just want to LS a directory and
I want to display all the contents into a list format

382
00:26:02,180 --> 00:26:05,040
and in a human readable thing.

383
00:26:05,260 --> 00:26:07,400
And it's fine. Like it's not
that long of a command.

384
00:26:07,400 --> 00:26:10,300
But as you start building longer
and longer commands,

385
00:26:10,320 --> 00:26:14,440
it can become kind of bothersome having
to retype them again and again.

386
00:26:14,440 --> 00:26:17,540
This is one of the reasons
why aliases are useful.

387
00:26:17,540 --> 00:26:21,740
Alias is a command that will
be a built-in in your shell,

388
00:26:21,960 --> 00:26:23,680
and what it will do is

389
00:26:23,680 --> 00:26:27,540
it will remap a short sequence of
characters to a longer sequence.

390
00:26:27,780 --> 00:26:31,500
So if I do, for example, here

391
00:26:31,500 --> 00:26:36,840
alias ll="ls -lah"

392
00:26:37,440 --> 00:26:42,520
If I execute this command, this is gonna call
the "alias" command with this argument

393
00:26:42,520 --> 00:26:44,320
and the LS is going to update

394
00:26:44,540 --> 00:26:49,040
the environment in my shell
to be aware of this mapping.

395
00:26:49,320 --> 00:26:52,920
So if I now do LL,

396
00:26:52,920 --> 00:26:57,520
it's executing that command without me
having to type the entire command.

397
00:26:57,720 --> 00:27:01,180
It can be really handy for many, many reasons.

398
00:27:01,180 --> 00:27:04,740
One thing to note before I go any further is that

399
00:27:05,000 --> 00:27:09,960
here, alias is not anything special
compared to other commands,

400
00:27:09,960 --> 00:27:11,400
it's just taking a single argument.

401
00:27:11,680 --> 00:27:15,600
And there is no space around
this equals and that's

402
00:27:16,020 --> 00:27:18,720
because alias takes a single argument

403
00:27:18,720 --> 00:27:21,640
and if you try doing

404
00:27:21,960 --> 00:27:25,120
something like this, that's giving
it more than one argument

405
00:27:25,120 --> 00:27:28,360
and that's not gonna work because
that's not the format it expects.

406
00:27:29,520 --> 00:27:33,680
So other use cases that work for aliases,

407
00:27:34,720 --> 00:27:36,549
as I was saying,

408
00:27:36,549 --> 00:27:39,920
for some things it may be much more convenient,

409
00:27:40,040 --> 00:27:41,020
like

410
00:27:41,020 --> 00:27:43,200
one of my favorites is git status.

411
00:27:43,200 --> 00:27:47,500
It's extremely long, and I don't like typing
that long of a command every so often,

412
00:27:47,560 --> 00:27:48,960
because you end up taking a lot of time.

413
00:27:49,120 --> 00:27:53,000
So GS will replace for doing the git status

414
00:27:53,820 --> 00:27:58,620
You can also use them to alias
things that you mistype often,

415
00:27:58,620 --> 00:28:01,160
so you can do "sl=ls",

416
00:28:01,160 --> 00:28:02,540
that will work.

417
00:28:05,800 --> 00:28:10,620
Other useful mappings are,

418
00:28:10,680 --> 00:28:15,460
you might want to alias a command to itself

419
00:28:15,740 --> 00:28:17,520
but with a default flag.

420
00:28:17,520 --> 00:28:21,100
So here what is going on is I'm creating an alias

421
00:28:21,100 --> 00:28:23,100
which is an alias for the move command,

422
00:28:23,300 --> 00:28:29,780
which is MV and I'm aliasing it to the
same command but adding the "-i" flag.

423
00:28:29,980 --> 00:28:34,460
And this "-i" flag, if you go through the man page
and look at it, it stands for "interactive".

424
00:28:34,780 --> 00:28:39,880
And what it will do is it will prompt
me before I do an overwrite.

425
00:28:39,880 --> 00:28:44,420
So once I have executed this,
I can do something like

426
00:28:44,700 --> 00:28:47,360
I want to move "aliases" into "case".

427
00:28:47,700 --> 00:28:53,140
By default "move" won't ask, and if "case"
already exists, it will be over.

428
00:28:53,160 --> 00:28:55,780
That's fine, I'm going to overwrite
whatever that's there.

429
00:28:56,020 --> 00:28:58,580
But here it's now expanded,

430
00:28:58,580 --> 00:29:01,660
"move" has been expanded into this "move -i"

431
00:29:01,660 --> 00:29:03,540
and it's using that to ask me

432
00:29:03,540 --> 00:29:07,400
"Oh, are you sure you want to overwrite this?"

433
00:29:07,700 --> 00:29:11,780
And I can say no, I don't want to lose that file.

434
00:29:12,180 --> 00:29:15,820
Lastly, you can use "alias move"

435
00:29:15,820 --> 00:29:18,520
to ask for what this alias stands for.

436
00:29:19,100 --> 00:29:22,060
So it will tell you so you can quickly make sure

437
00:29:22,080 --> 00:29:25,400
what the command that you
are executing actually is.

438
00:29:27,040 --> 00:29:31,400
One inconvenient part about, for example,
having aliases is how will you go about

439
00:29:31,760 --> 00:29:35,340
persisting them into your current environment?

440
00:29:35,500 --> 00:29:38,120
Like, if I were to close this terminal now,

441
00:29:38,280 --> 00:29:40,160
all these aliases will go away.

442
00:29:40,160 --> 00:29:43,020
And you don't want to be kind
of retyping these commands

443
00:29:43,020 --> 00:29:46,760
and more generally, if you start configuring
your shell more and more,

444
00:29:46,860 --> 00:29:50,880
you want some way of bootstrapping
all this configuration.

445
00:29:51,380 --> 00:29:56,780
You will find that most shell command programs

446
00:29:56,880 --> 00:30:01,440
will use some sort of text
based configuration file.

447
00:30:01,440 --> 00:30:06,740
And this is what we usually call "dotfiles", because
they start with a dot for historical reasons.

448
00:30:07,060 --> 00:30:13,160
So for bash in our case, which is a shell,

449
00:30:13,160 --> 00:30:15,560
we can look at the bashrc.

450
00:30:16,180 --> 00:30:19,840
For demonstration purposes,
here I have been using ZSH,

451
00:30:19,900 --> 00:30:24,460
which is a different shell, and I'm going
to be configuring bash, and starting bash.

452
00:30:24,640 --> 00:30:29,640
So if I create an entry here and I say

453
00:30:29,940 --> 00:30:31,960
SL maps to LS

454
00:30:32,600 --> 00:30:36,020
And I have modified that, and now I start bash.

455
00:30:36,540 --> 00:30:40,660
Bash is kind of completely unconfigured,
but now if I do SL...

456
00:30:41,360 --> 00:30:44,040
Hm, that's unexpected.

457
00:30:46,280 --> 00:30:48,000
Oh, good. Good getting that.

458
00:30:48,300 --> 00:30:52,200
So it matters where you config file is,

459
00:30:52,200 --> 00:30:55,260
your config file needs to be in your home folder.

460
00:30:55,640 --> 00:31:00,940
So your configuration file for
bash will live in that "~",

461
00:31:00,940 --> 00:31:03,940
which will expand to your home directory,

462
00:31:03,940 --> 00:31:05,560
and then bashrc.

463
00:31:06,160 --> 00:31:08,840
And here we can create the alias

464
00:31:12,040 --> 00:31:15,840
and now we start a bash session and we do SL.

465
00:31:15,840 --> 00:31:21,500
Now it has been loaded, and this is
loaded at the beginning when this

466
00:31:22,300 --> 00:31:24,300
bash program is started.

467
00:31:24,700 --> 00:31:31,200
All this configuration is loaded and you can, not only use
aliases, they can have a lot of parts of configuration.

468
00:31:31,390 --> 00:31:35,729
So for example here, I have a prompt
which is fairly useless.

469
00:31:35,730 --> 00:31:38,429
It has just given me the name
of the shell, which is bash,

470
00:31:38,640 --> 00:31:43,820
and the version, which is 5.0. I don't
want this to be displayed and

471
00:31:44,360 --> 00:31:48,540
as with many things in your shell, this
is just an environment variable.

472
00:31:48,600 --> 00:31:53,120
So the "PS1" is just the prompt string

473
00:31:53,710 --> 00:31:55,480
for your prompt and

474
00:31:55,480 --> 00:32:02,520
we can actually modify this
to just be a "> " symbol.

475
00:32:02,520 --> 00:32:08,280
and now that has been modified, and we have
that. But if we exit and call bash again,

476
00:32:08,620 --> 00:32:15,059
that was lost. However, if we add this
entry and say, oh we want "PS1"

477
00:32:15,760 --> 00:32:17,230
to be

478
00:32:17,230 --> 00:32:19,179
this and

479
00:32:19,179 --> 00:32:24,689
we call bash again, this has been persisted.
And we can keep modifying this configuration.

480
00:32:25,090 --> 00:32:27,209
So maybe we want to include

481
00:32:27,880 --> 00:32:29,880
where the

482
00:32:30,370 --> 00:32:32,939
working directory that we are is in, and

483
00:32:34,140 --> 00:32:37,380
that's telling us the same information
that we had in the other shell.

484
00:32:37,380 --> 00:32:40,480
And there are many, many options,

485
00:32:40,780 --> 00:32:45,060
shells are highly, highly configurable, and

486
00:32:45,700 --> 00:32:49,920
it's not only cells that are configured
through these files,

487
00:32:50,590 --> 00:32:55,740
there are many other programs. As we saw for
example in the editors lecture, Vim is also

488
00:32:55,840 --> 00:33:02,900
configured this way. We gave you this vimrc
file and told you to put it under your

489
00:33:03,460 --> 00:33:06,380
home/.vimrc

490
00:33:06,380 --> 00:33:11,800
and this is the same concept, but just
for Vim. It's just giving it a set of

491
00:33:12,160 --> 00:33:18,340
instructions that it should load when it's started,
so you can keep a configuration that you want.

492
00:33:19,140 --> 00:33:21,240
And even non...

493
00:33:21,580 --> 00:33:27,140
kind of a lot of programs will support this. For instance,
my terminal emulator, which is another concept,

494
00:33:27,260 --> 00:33:30,159
which is the program that is

495
00:33:30,159 --> 00:33:35,459
running the shell, in a way, and displaying
this into the screen in my computer.

496
00:33:35,950 --> 00:33:38,610
It can also be configured this way, so

497
00:33:39,940 --> 00:33:43,620
if I modify this I can

498
00:33:46,510 --> 00:33:53,279
change the size of the font. Like right now, for
example, I have increased the font size a lot

499
00:33:53,279 --> 00:33:55,768
for demonstration purposes, but

500
00:33:56,440 --> 00:34:00,360
if I change this entry and make it for example

501
00:34:01,320 --> 00:34:06,820
28 and write this value, you see that
the size of the font has changed,

502
00:34:06,820 --> 00:34:12,920
because I edited this text file that specifies
how my terminal emulator should work.

503
00:34:19,480 --> 00:34:20,900
Any questions so far?

504
00:34:20,900 --> 00:34:22,280
With dotfiles.

505
00:34:28,040 --> 00:34:35,940
Okay, it can be a bit daunting knowing that there
is like this endless wall of configurations,

506
00:34:35,940 --> 00:34:40,600
and how do you go about learning
about what can be configured?

507
00:34:42,020 --> 00:34:44,300
The good news is that

508
00:34:44,640 --> 00:34:48,900
we have linked you to really good
resources in the lecture notes.

509
00:34:48,960 --> 00:34:56,440
But the main idea is that a lot of people really like
just configuring these tools and have uploaded

510
00:34:56,640 --> 00:35:01,140
their configuration files to GitHub, another
different kind of repositories online.

511
00:35:01,140 --> 00:35:03,300
So for example, here we are on GitHub,

512
00:35:03,300 --> 00:35:06,640
we search for dotfiles, and
can see that there are like

513
00:35:06,780 --> 00:35:12,540
thousands of repositories of people sharing
their configuration files. We have also...

514
00:35:12,540 --> 00:35:15,460
Like, the class instructors
have linked our dotfiles.

515
00:35:15,460 --> 00:35:19,420
So if you really want to know how
any part of our setup is working

516
00:35:19,420 --> 00:35:22,220
you can go through it and try to figure it out.

517
00:35:22,220 --> 00:35:24,220
You can also feel free to ask us.

518
00:35:24,380 --> 00:35:27,060
If we go for example to this repository here

519
00:35:27,210 --> 00:35:30,649
we can see that there's many, many
files that you can configure.

520
00:35:30,650 --> 00:35:37,520
For example, there is one for bash, the first couple of ones
are for git, that will be probably be covered in the

521
00:35:38,610 --> 00:35:40,819
version control lecture tomorrow.

522
00:35:41,400 --> 00:35:48,500
If we go for example to the bash profile, which is
a different form of what we saw in the bashrc,

523
00:35:49,400 --> 00:35:52,900
it can be really useful because
you can learn through

524
00:35:53,940 --> 00:35:58,320
just looking at the manual page, but the
manual pages is, a lot of the time

525
00:35:58,480 --> 00:36:03,520
just kind of like a descriptive explanation
of all the different options

526
00:36:03,520 --> 00:36:04,880
and sometimes it's more helpful

527
00:36:04,880 --> 00:36:09,600
going through examples of what people have done
and trying to understand why they did it

528
00:36:09,600 --> 00:36:12,200
and how it's helping their workflow.

529
00:36:12,960 --> 00:36:17,300
We can say here that this person has
done case-insensitive globbing.

530
00:36:17,320 --> 00:36:21,220
We covered globbing as this
kind of filename expansion

531
00:36:22,100 --> 00:36:25,760
trick in the shell scripting and tools.

532
00:36:25,900 --> 00:36:28,800
And here you say no, I don't want this to matter,

533
00:36:28,800 --> 00:36:30,760
whether using uppercase and lowercase,

534
00:36:30,760 --> 00:36:32,760
and just setting this option in the shell
for these things to work this way

535
00:36:35,360 --> 00:36:38,140
Similarly, there is for example aliases.

536
00:36:38,140 --> 00:36:42,220
Here you can see a lot of aliases that this
person is doing. For example, "d" for

537
00:36:44,200 --> 00:36:47,400
"d" for "Dropbox", sorry, because
that's just much shorter.

538
00:36:47,400 --> 00:36:49,200
"g" for "git"...

539
00:36:49,740 --> 00:36:54,560
Say we go, for example, with vimrc. It
can be actually very, very informative,

540
00:36:54,560 --> 00:36:58,860
going through this and trying
to extract useful information.

541
00:36:59,000 --> 00:37:06,420
We do not recommend just kind of getting one huge blob
of this and copying this into your config files,

542
00:37:07,110 --> 00:37:12,439
because maybe things are prettier, but you might
not really understand what is going on.

543
00:37:15,150 --> 00:37:19,579
Lastly one thing I want to mention
about dotfiles is that

544
00:37:20,460 --> 00:37:23,390
people not only try to push these

545
00:37:24,660 --> 00:37:28,849
files into GitHub just so other
people can read it, that's

546
00:37:29,400 --> 00:37:33,319
one reason. They also make really sure they can

547
00:37:34,140 --> 00:37:39,440
reproduce their setup. And to do that
they use a slew of different tools.

548
00:37:39,440 --> 00:37:41,280
Oops, went a little too far.

549
00:37:41,280 --> 00:37:44,840
So GNU Stow is, for example, one of them

550
00:37:45,720 --> 00:37:49,060
and the trick that they are doing is

551
00:37:50,280 --> 00:37:54,520
they are kind of putting all their
dotfiles in a folder and they are

552
00:37:55,200 --> 00:37:59,520
faking to the system, using
a tool called symlinks,

553
00:37:59,520 --> 00:38:02,440
that they are actually what
they're not. I'm gonna

554
00:38:03,150 --> 00:38:05,150
draw really quick what I mean by that.

555
00:38:05,790 --> 00:38:10,939
So a common folder structure might look
like you have your home folder and

556
00:38:11,670 --> 00:38:14,300
in this home folder you might have your

557
00:38:16,050 --> 00:38:21,380
bashrc, that contains your bash configuration,
you might have your vimrc and

558
00:38:22,500 --> 00:38:25,760
it would be really great if you could
keep this under version control.

559
00:38:26,580 --> 00:38:29,300
But the thing is, you might not
want to have a git repository,

560
00:38:29,300 --> 00:38:31,300
which will be covered tomorrow,

561
00:38:31,300 --> 00:38:32,300
in your home folder.

562
00:38:32,300 --> 00:38:37,360
So what people usually do is they
create a dotfiles repository,

563
00:38:38,280 --> 00:38:42,160
and then they have entries here for their

564
00:38:43,050 --> 00:38:47,239
bashrc and their vimrc. And
this is where actually

565
00:38:47,820 --> 00:38:49,820
the files are

566
00:38:50,100 --> 00:38:52,400
and what they are doing is they're just

567
00:38:53,460 --> 00:38:56,510
telling the OS to forward, whenever anyone

568
00:38:56,760 --> 00:39:01,849
wants to read this file or write to this file,
just forward this to this other file.

569
00:39:03,000 --> 00:39:05,719
This is a concept called symlinks

570
00:39:06,690 --> 00:39:08,630
and it's useful in this scenario,

571
00:39:08,630 --> 00:39:12,600
but it in general it's a really
useful tool in UNIX

572
00:39:12,700 --> 00:39:14,700
that we haven't covered so far in the lectures

573
00:39:14,960 --> 00:39:16,740
but you might be...

574
00:39:16,740 --> 00:39:18,740
that you should be familiar with.

575
00:39:19,100 --> 00:39:22,840
And in general, the syntax will be "ln -s"

576
00:39:22,840 --> 00:39:29,980
for specifying a symbolic link and then
you will put the path to the file

577
00:39:30,570 --> 00:39:33,049
that you want to create and then the

578
00:39:33,780 --> 00:39:35,780
symlink that you want to create.

579
00:39:39,390 --> 00:39:41,390
And

580
00:39:41,880 --> 00:39:45,619
All these all these kind of fancy tools
that we're seeing here listed,

581
00:39:45,810 --> 00:39:52,159
they all amount to doing some sort of this trick, so
that you can have all your dotfiles neat and tidy

582
00:39:52,680 --> 00:39:57,829
into a folder, and then they can be
version-controlled, and they can be

583
00:39:58,349 --> 00:40:02,689
symlinked so the rest of the programs can
find them in their default locations.

584
00:40:06,720 --> 00:40:09,020
Any questions regarding dotfiles?

585
00:40:13,200 --> 00:40:20,200
Do you need to have the dotfiles in your home folder,
and then also dotfiles in the version control folder?

586
00:40:20,780 --> 00:40:24,640
So what you will have is,
pretty much every program,

587
00:40:24,640 --> 00:40:26,180
for example bash,

588
00:40:26,180 --> 00:40:29,560
will always look for "home/.bashrc".

589
00:40:29,560 --> 00:40:33,480
That's where the program is going to look for.

590
00:40:33,820 --> 00:40:40,200
What you do when you do a symlink
is, you place your "home/.bashrc"

591
00:40:40,200 --> 00:40:44,900
it's just a file that is kind
of a special file in UNIX,

592
00:40:45,150 --> 00:40:49,609
that says oh, whenever you want to read
this file go to this other file.

593
00:40:51,500 --> 00:40:53,440
There's no content, like there is no...

594
00:40:53,600 --> 00:40:58,099
your aliases are not part of this dotfile. That file
is just kind of like a pointer, saying now you should

595
00:40:58,100 --> 00:40:59,400
go that other way.

596
00:40:59,400 --> 00:41:02,600
And by doing that you can have your other file

597
00:41:02,600 --> 00:41:04,400
in that other folder.

598
00:41:04,560 --> 00:41:06,360
If version controlling is not useful, think about

599
00:41:06,360 --> 00:41:10,740
what if you want to have them in your Dropbox
folder, so they're synced to the cloud,

600
00:41:10,759 --> 00:41:15,019
for example. That's kind of another use case
where like symlinks could be really useful

601
00:41:16,240 --> 00:41:21,040
So you don't need the folder dotfiles
to be in the home directory, right?

602
00:41:21,040 --> 00:41:23,820
Because you can just use the symlink,
that points somewhere else.

603
00:41:23,960 --> 00:41:29,760
As long as you have a way for the default path
to resolve wherever you have it, yeah.

604
00:41:35,100 --> 00:41:38,000
Last thing I want to cover in the lecture...

605
00:41:38,000 --> 00:41:40,380
Oh, sorry, any other questions about dotfiles?

606
00:41:49,200 --> 00:41:52,580
Last thing I want to cover in the lecture
is working with remote machines,

607
00:41:52,580 --> 00:41:55,549
which is a thing that you will run into,

608
00:41:55,559 --> 00:41:56,900
sooner or later.

609
00:41:56,900 --> 00:42:02,238
And there are a few things that will make your life
much easier when dealing with remote machines

610
00:42:03,180 --> 00:42:05,180
if you know about them.

611
00:42:05,220 --> 00:42:08,380
Right now maybe because you are
using the Athena cluster,

612
00:42:08,380 --> 00:42:10,740
but later on, during your programming career,

613
00:42:10,740 --> 00:42:11,960
it's pretty sure that

614
00:42:11,960 --> 00:42:15,400
there is a fairly ubiquitous
concept of having your

615
00:42:15,400 --> 00:42:20,380
local working environment and then having some
production server that is actually running the

616
00:42:20,970 --> 00:42:23,239
code, so it is really good to get familiar

617
00:42:24,480 --> 00:42:26,749
about how to work in/with remote machines.

618
00:42:27,420 --> 00:42:35,180
So the main command for working
with remote machines is SSH.

619
00:42:37,760 --> 00:42:43,900
SSH is just like a secure shell, it's
just gonna take the responsibility for

620
00:42:43,900 --> 00:42:46,540
reaching wherever we want or tell it to go

621
00:42:47,560 --> 00:42:50,700
and trying to open a session there.

622
00:42:50,700 --> 00:42:52,400
So here the syntax is:

623
00:42:53,130 --> 00:42:56,660
"JJGO" is the user that I want
to use in the remote machine,

624
00:42:56,660 --> 00:42:58,430
and this is because the user is

625
00:42:58,529 --> 00:43:03,460
different from the one I have my local machine,
which will be the case a lot of the time,

626
00:43:03,460 --> 00:43:07,400
then the "@" is telling the
terminal that this separates

627
00:43:07,400 --> 00:43:12,540
what the user is from what the address is.

628
00:43:12,540 --> 00:43:16,540
And here I'm using an IP address because
what I'm actually doing is

629
00:43:16,540 --> 00:43:20,500
I have a virtual machine in my computer,

630
00:43:20,500 --> 00:43:23,240
that is the one that is remote right now.

631
00:43:23,240 --> 00:43:26,400
And I'm gonna be SSH'ing into it. This is the

632
00:43:26,580 --> 00:43:27,880
URL that I'm using,

633
00:43:27,880 --> 00:43:29,860
sorry, the IP that I'm using,

634
00:43:29,860 --> 00:43:32,280
but you might also see things like

635
00:43:32,360 --> 00:43:36,820
oh I want to SSH as "JJGO"

636
00:43:36,820 --> 00:43:39,840
at "foobar.mit.edu"

637
00:43:39,840 --> 00:43:42,960
That's probably something more
common, if you are using some

638
00:43:42,960 --> 00:43:47,260
remote server that has a DNS name.

639
00:43:48,180 --> 00:43:51,860
So going back to a regular command,

640
00:43:53,220 --> 00:43:56,580
we try to SSH, it asks us for a password,

641
00:43:56,580 --> 00:43:58,180
really common thing.

642
00:43:58,190 --> 00:43:59,480
And now we're there. We have...

643
00:43:59,480 --> 00:44:02,629
we're still in our same terminal emulator

644
00:44:02,630 --> 00:44:09,529
but right now SSH is kind of forwarding the
entire virtual display to display what the

645
00:44:09,869 --> 00:44:14,358
remote shell is displaying. And
we can execute commands here and

646
00:44:15,630 --> 00:44:17,630
we'll see the remote files

647
00:44:18,390 --> 00:44:22,819
A couple of handy things to know about
SSH, that were briefly covered in the

648
00:44:23,220 --> 00:44:27,080
data wrangling lecture, is that
SSH is not only good for just

649
00:44:28,280 --> 00:44:33,760
opening connections. It will also let
you just execute commands remotely.

650
00:44:33,770 --> 00:44:36,979
So for example, if I do that, it's gonna ask me

651
00:44:37,710 --> 00:44:39,020
what is my password?, again.

652
00:44:39,020 --> 00:44:41,059
And it's executing this command

653
00:44:41,279 --> 00:44:43,420
then coming back to my terminal

654
00:44:43,420 --> 00:44:47,420
and piping the output of what that
command was, in the remote machine,

655
00:44:47,420 --> 00:44:50,480
through the standard output in my current cell.

656
00:44:50,480 --> 00:44:53,940
And I could have this in...

657
00:44:58,100 --> 00:45:00,480
I could have this in a pipe, and

658
00:45:00,980 --> 00:45:03,580
this will work and we'll just

659
00:45:03,600 --> 00:45:06,100
drop all this output and then have a local pipe

660
00:45:06,100 --> 00:45:07,879
where I can keep working.

661
00:45:08,640 --> 00:45:12,140
So far, it has been kind of inconvenient,
having to type our password.

662
00:45:12,630 --> 00:45:14,820
There's one really good trick for this.

663
00:45:14,820 --> 00:45:16,880
It's we can use something called "SSH keys".

664
00:45:17,140 --> 00:45:20,660
SSH keys just use public key encryption

665
00:45:20,660 --> 00:45:24,980
to create a pair of SSH keys, a public
key and a private key, and then

666
00:45:25,170 --> 00:45:29,320
you can give the server the
public part of the key.

667
00:45:29,320 --> 00:45:32,810
So you copy the public key and
then whenever you try to

668
00:45:33,390 --> 00:45:37,129
authenticate instead of using your password,
it's gonna use the private key to

669
00:45:37,820 --> 00:45:40,800
prove to the server that you are
actually who you say you are.

670
00:45:43,860 --> 00:45:48,020
We can quickly showcase how you will go

671
00:45:48,020 --> 00:45:49,400
about doing this.

672
00:45:49,400 --> 00:45:53,180
Right now I don't have any SSH keys,
so I'm gonna create a couple of them.

673
00:45:53,940 --> 00:45:58,250
First thing, it's just gonna ask
me where I want this key to live.

674
00:45:58,980 --> 00:46:00,640
Unsurprisingly, it's doing this.

675
00:46:00,640 --> 00:46:04,820
This is my home folder and then
it's using this ".ssh" path,

676
00:46:05,460 --> 00:46:08,750
which refers back to the same concept
that we covered earlier about having

677
00:46:08,850 --> 00:46:12,439
dotfiles. Like ".ssh" is a folder
that contains a lot of the

678
00:46:13,320 --> 00:46:16,540
configuration files for how
you want SSH to behave.

679
00:46:17,060 --> 00:46:19,420
So it will ask us a passphrase.

680
00:46:19,680 --> 00:46:23,120
The passphrase is to encrypt
the private part of the key

681
00:46:23,120 --> 00:46:27,160
because if someone gets your private key,
if you don't have a password protected

682
00:46:27,920 --> 00:46:29,580
private key, if they get that key

683
00:46:29,580 --> 00:46:32,240
they can use that key to impersonate
you in any server.

684
00:46:32,310 --> 00:46:34,360
Whereas if you add a passphrase,

685
00:46:34,360 --> 00:46:37,640
they will have to know what the passphrase
is to actually use the key.

686
00:46:40,800 --> 00:46:51,740
It has created a keeper. We can check that
these two files are now under ssh.

687
00:46:51,740 --> 00:46:53,920
And we can see...

688
00:46:57,720 --> 00:47:02,960
We have these two files: we have
the 25519 and the public key.

689
00:47:03,320 --> 00:47:06,300
And if we "cat" through the output,

690
00:47:06,300 --> 00:47:09,760
that key is actually not like
any fancy binary file, it's

691
00:47:15,430 --> 00:47:20,760
just a text file that has the contents
of the public key and some

692
00:47:23,050 --> 00:47:26,729
alias name for it, so we can
know what this public key is.

693
00:47:26,950 --> 00:47:32,220
The way we can tell the server that
we're authorized to SSH there

694
00:47:32,260 --> 00:47:38,400
is by just actually copying this file,
like copying this string into a file,

695
00:47:38,400 --> 00:47:41,540
that is ".ssh/authorized_keys".

696
00:47:42,100 --> 00:47:46,160
So here what I'm doing is I'm

697
00:47:46,960 --> 00:47:49,770
catting the output of this file

698
00:47:49,800 --> 00:47:53,920
which is just this line of
text that we want to copy

699
00:47:53,920 --> 00:47:57,440
and I'm piping that into SSH and then remotely

700
00:47:57,960 --> 00:48:02,080
I'm asking "tee" to dump the contents
of the standard input

701
00:48:02,080 --> 00:48:05,220
into ".ssh/authorized_keys".

702
00:48:05,440 --> 00:48:10,360
And if we do that, obviously it's
gonna ask us for a password.

703
00:48:14,800 --> 00:48:18,740
It was copied, and now we
can check that if we try

704
00:48:19,690 --> 00:48:21,690
to SSH again,

705
00:48:21,960 --> 00:48:24,840
It's going to first ask us for a passphrase

706
00:48:24,840 --> 00:48:29,100
but you can arrange that so that
it's saved in the session

707
00:48:29,460 --> 00:48:34,840
and we didn't actually have to
type the key for the server.

708
00:48:34,840 --> 00:48:36,840
And I can kind of show that again.

709
00:48:45,820 --> 00:48:47,540
More things that are useful.

710
00:48:47,540 --> 00:48:49,040
Oh, we can do...

711
00:48:49,220 --> 00:48:51,880
If that command seemed a little bit janky,

712
00:48:51,980 --> 00:48:55,000
you can actually use this command
that is built for this,

713
00:48:55,000 --> 00:49:00,640
so you don't have to kind of
craft this "ssh tee" command.

714
00:49:00,640 --> 00:49:03,800
That is just called "ssh-copy-id".

715
00:49:05,000 --> 00:49:08,080
And we can do the same

716
00:49:08,080 --> 00:49:09,660
and it's gonna copy the key.

717
00:49:09,660 --> 00:49:14,280
And now, if we try to SSH,

718
00:49:14,500 --> 00:49:18,320
we can SSH without actually
typing any key at all,

719
00:49:18,860 --> 00:49:20,320
or any password.

720
00:49:20,660 --> 00:49:21,520
More things.

721
00:49:21,520 --> 00:49:23,520
We will probably want to copy files.

722
00:49:23,740 --> 00:49:25,310
You cannot use "CP"

723
00:49:25,310 --> 00:49:29,720
but you can use "SCP", for "SSH copy".

724
00:49:29,720 --> 00:49:34,500
And here we can specify that we want
to copy this local file called notes

725
00:49:34,500 --> 00:49:36,880
and the syntax is kind of similar.

726
00:49:36,880 --> 00:49:39,760
We want to copy to this remote and

727
00:49:39,920 --> 00:49:44,020
then we have a semicolon to separate
what the path is going to be.

728
00:49:44,020 --> 00:49:45,040
And then we have

729
00:49:45,040 --> 00:49:46,620
oh, we want to copy this as notes

730
00:49:46,620 --> 00:49:51,000
but we could also copy this as foobar.

731
00:49:51,740 --> 00:49:55,600
And if we do that, it has been executed

732
00:49:55,780 --> 00:49:59,280
and it's telling us that all the
contents have been copied there.

733
00:49:59,540 --> 00:50:02,200
If you're gonna be copying a lot of files,

734
00:50:02,200 --> 00:50:05,100
there is a better command
that you should be using

735
00:50:05,100 --> 00:50:07,740
that is called "RSYNC". For example, here

736
00:50:07,900 --> 00:50:10,780
just by specifying these three flags,

737
00:50:10,820 --> 00:50:15,960
I'm telling RSYNC to kind of preserve
all the permissions whenever possible

738
00:50:16,240 --> 00:50:19,740
to try to check if the file
has already been copied.

739
00:50:19,740 --> 00:50:24,100
For example, SCP will try to copy
files that are already there.

740
00:50:24,200 --> 00:50:26,440
This will happen for example
if you are trying to copy

741
00:50:26,440 --> 00:50:29,060
and the connection interrupts
in the middle of it.

742
00:50:29,120 --> 00:50:32,060
SCP will start from the very beginning,
trying to copy every file,

743
00:50:32,080 --> 00:50:36,600
whereas RSYNC will continue
from where it stopped.

744
00:50:37,240 --> 00:50:38,440
And here,

745
00:50:39,060 --> 00:50:42,760
we ask it to copy the entire folder and

746
00:50:43,780 --> 00:50:46,560
it's just really quickly
copied the entire folder.

747
00:50:48,080 --> 00:50:54,100
One of the other things to know about SSH is that

748
00:50:54,320 --> 00:50:59,860
the equivalent of the dot file
for SSH is the "SSH config".

749
00:50:59,860 --> 00:51:06,340
So if we edit the SSH config to be

750
00:51:13,120 --> 00:51:17,940
If I edit the SSH config to
look something like this,

751
00:51:17,940 --> 00:51:22,900
instead of having to, every
time, type "ssh jjgo",

752
00:51:23,040 --> 00:51:27,760
having this really long string so I can
like refer to this specific remote,

753
00:51:27,760 --> 00:51:30,140
I want to refer, with the specific user name,

754
00:51:30,140 --> 00:51:32,760
I can have something here that says

755
00:51:33,160 --> 00:51:35,680
this is the username, this
is the host name, that this

756
00:51:36,860 --> 00:51:40,540
host is referring to and you should
use this identity file.

757
00:51:41,460 --> 00:51:43,960
And if I copy this,

758
00:51:43,960 --> 00:51:46,100
this is right now in my local folder,

759
00:51:46,100 --> 00:51:49,000
I can copy this into ssh.

760
00:51:49,600 --> 00:51:53,520
Now, instead of having to do this really
long command, I can just say

761
00:51:53,520 --> 00:51:57,100
I just want to SSH into the host called VM.

762
00:51:58,260 --> 00:52:03,220
And by doing that, it's grabbing all that
configuration from the SSH config

763
00:52:03,220 --> 00:52:05,220
and applying it here.

764
00:52:05,240 --> 00:52:10,060
This solution is much better than something
like creating an alias for SSH,

765
00:52:10,360 --> 00:52:13,360
because other programs like SCP and RSYNC

766
00:52:13,360 --> 00:52:19,440
also know about the dotfiles for SSH and
will use them whenever they are there.

767
00:52:22,820 --> 00:52:30,400
Last thing I want to cover about remote machines is
that here, for example, we'll have tmux and we can,

768
00:52:31,760 --> 00:52:35,780
like I was saying before, we
can start editing some file

769
00:52:39,160 --> 00:52:44,500
and we can start running some job.

770
00:52:54,200 --> 00:52:56,180
For example, something like HTOP.

771
00:52:56,180 --> 00:52:58,720
And this is running here, we can

772
00:52:59,320 --> 00:53:01,320
detach from it,

773
00:53:01,430 --> 00:53:03,430
close the connection and

774
00:53:03,740 --> 00:53:07,780
then SSH back. And then, if you do "tmux a",

775
00:53:07,780 --> 00:53:11,340
everything is as you left it, like
nothing has really changed.

776
00:53:11,340 --> 00:53:15,220
And if you have things executing there in
the background, they will keep executing.

777
00:53:17,500 --> 00:53:23,300
I think that, pretty much, ends
all I have to say for this tool.

778
00:53:23,300 --> 00:53:26,420
Any questions related to remote machines?

779
00:53:32,860 --> 00:53:36,780
That's a really good question.
So what I do for that,

780
00:53:38,700 --> 00:53:39,460
Oh, yes, sorry.

781
00:53:39,460 --> 00:53:44,880
So the question is, how do you deal with
trying to use tmux in your local machine,

782
00:53:44,880 --> 00:53:47,640
and also trying to use tmux
in the remote machine?

783
00:53:48,400 --> 00:53:50,760
There are a couple of tricks
for dealing with that.

784
00:53:50,760 --> 00:53:53,220
The first one is changing the prefix.

785
00:53:53,360 --> 00:53:55,340
So what I do, for example, is

786
00:53:55,340 --> 00:54:00,020
in my local machine the prefix I have
changed from "Ctrl+B" to "Ctrl+A" and

787
00:54:00,220 --> 00:54:02,580
then in remove machines this is still "Ctrl+B".

788
00:54:02,800 --> 00:54:05,580
So I can kind of swap between,

789
00:54:05,580 --> 00:54:09,840
if I want to do things to the
local tmux I will do "Ctrl+A"

790
00:54:09,840 --> 00:54:13,460
and if I want to do things to the
remote tmux I would do "Ctrl+B".

791
00:54:15,080 --> 00:54:19,900
Another thing is that you
can have separate configs,

792
00:54:20,080 --> 00:54:24,100
so I can do something like this, and then...

793
00:54:27,260 --> 00:54:31,040
Ah, because I don't have my own ssh config, yeah.

794
00:54:32,240 --> 00:54:33,000
But if you...

795
00:54:33,000 --> 00:54:34,420
Um, I can SSH "VM".

796
00:54:36,820 --> 00:54:38,900
Here, what you see,

797
00:54:38,900 --> 00:54:41,000
the difference between these
two bars, for example,

798
00:54:41,000 --> 00:54:43,680
is because the tmux config is different.

799
00:54:44,380 --> 00:54:48,500
As you will see in the exercises,
the tmux configuration is in

800
00:54:50,320 --> 00:54:53,780
the tmux.conf

801
00:54:56,720 --> 00:54:58,140
And in tmux.conf,

802
00:54:58,140 --> 00:55:02,020
here you can do a lot of things like changing
the color depending on the host you are

803
00:55:02,210 --> 00:55:06,879
so you can get like quick visual
feedback about where you are, or

804
00:55:06,880 --> 00:55:10,240
if you have a nested session. Also, tmux will,

805
00:55:10,520 --> 00:55:15,280
if you're in the same host and you
try to tmux within a tmux session,

806
00:55:15,290 --> 00:55:18,759
it will kind of prevent you from doing
it so you don't run into issues.

807
00:55:21,700 --> 00:55:25,400
Any other questions related, to kind
of all the topics we have covered.

808
00:55:29,100 --> 00:55:32,720
Another answer to that question is
also, if you type the prefix twice,

809
00:55:32,880 --> 00:55:35,760
it sends it once to the underlying shell.

810
00:55:35,920 --> 00:55:40,100
So the local binding is "Ctrl+A" and
the remote binding is "Ctrl+A",

811
00:55:40,100 --> 00:55:45,260
You could type "Ctrl+A", "Ctrl+A" and then "D", for
example, detaches from the remote, basically.

812
00:55:52,480 --> 00:55:59,660
I think that ends the class for today, there's a bunch
of exercises related to all these main topics and

813
00:56:00,380 --> 00:56:05,410
we're gonna be holding office hours today, too.
So feel free to come and ask us any questions.