1
00:00:00,084 --> 00:00:02,470
The terminal is a text interface.

2
00:00:02,470 --> 00:00:05,870
By default,
terminals run a program called a shell.

3
00:00:05,870 --> 00:00:08,130
There are many different
shell programs available,

4
00:00:08,130 --> 00:00:13,870
most of them with names ending in SH,
like ZSH, KSH, and so on.

5
00:00:13,870 --> 00:00:17,310
Most operating systems today
run a shell called Bash, and

6
00:00:17,310 --> 00:00:19,330
that's what we're running here.

7
00:00:19,330 --> 00:00:21,910
All the different shells
work very similarly, so

8
00:00:21,910 --> 00:00:25,450
the things you'll learn in Bash will
be applicable in the other shells too.

9
00:00:26,570 --> 00:00:30,450
You can see a bunch of text here,
ending in a dollar sign.

10
00:00:30,450 --> 00:00:35,040
This is the shell prompt, the shell
is prompting you to type something.

11
00:00:35,040 --> 00:00:38,800
Most shell prompts end with a dollar sign,
like this.

12
00:00:38,800 --> 00:00:42,300
The blinking box following
the dollar sign is the cursor,

13
00:00:42,300 --> 00:00:44,870
it's the place the text
you type will appear.

14
00:00:44,870 --> 00:00:49,070
It mostly works like the cursors you've
seen in word processors and web forms, but

15
00:00:49,070 --> 00:00:51,030
with a few exceptions.

16
00:00:51,030 --> 00:00:53,702
You can type text with the letter
keys on your keyboard, and

17
00:00:53,702 --> 00:00:56,557
you can delete it with the backspace key.

18
00:00:56,557 --> 00:00:57,650
You can move back and

19
00:00:57,650 --> 00:01:02,100
forth within the text you've typed on this
line with the left and right arrow keys.

20
00:01:02,100 --> 00:01:06,270
But you can only type on this one line,
you can't move off of it.

21
00:01:06,270 --> 00:01:07,250
If you press the up and

22
00:01:07,250 --> 00:01:11,830
down arrow keys, it will instead cycle
through entries you've made previously.

23
00:01:11,830 --> 00:01:14,900
Here you can see it bringing
up commands I entered before.

24
00:01:14,900 --> 00:01:18,680
This is called command history, and we'll
talk about it more in an upcoming video.

25
00:01:19,950 --> 00:01:23,645
If I hit the Enter key without typing
anything, it won't really do anything,

26
00:01:23,645 --> 00:01:25,340
it'll just display another prompt.

27
00:01:26,640 --> 00:01:31,401
We can run commands at the prompt to
execute other programs inside the shell.

28
00:01:31,401 --> 00:01:34,890
The output of these commands
will be shown in the terminal.

29
00:01:34,890 --> 00:01:38,720
Because the shell offers you a single
line of text where you enter commands,

30
00:01:38,720 --> 00:01:41,200
this is often referred
to as the command line.

31
00:01:42,300 --> 00:01:46,950
Let's try running a program called ls,
which is used for listing files.

32
00:01:46,950 --> 00:01:49,820
I type ls and
press the Enter key to run the command.

33
00:01:50,830 --> 00:01:55,660
The program runs, and its output appears
on the terminal below the command line.

34
00:01:55,660 --> 00:01:59,110
The program prints out
the names of several files.

35
00:01:59,110 --> 00:02:03,130
Then the ls program finishes, and
we're returned to our shell prompt.

36
00:02:03,130 --> 00:02:05,380
The shell is ready for
us to type another command.

37
00:02:06,480 --> 00:02:08,310
Let's try running another program.

38
00:02:08,310 --> 00:02:10,390
This time we'll run the whoami command,

39
00:02:10,390 --> 00:02:12,440
which prints the name of
the current user account.

40
00:02:13,640 --> 00:02:16,610
It looks like we're logged in
as a user named treehouse.

41
00:02:17,640 --> 00:02:20,830
Once again, the program completes and
we're returned to the shell prompt.

42
00:02:21,890 --> 00:02:25,190
Now I'll run a program called cat,
which concatenates or

43
00:02:25,190 --> 00:02:27,200
joins the contents of files together.

44
00:02:28,760 --> 00:02:32,330
Normally, you'd provide the names of one
or more files you want cat to print out.

45
00:02:32,330 --> 00:02:36,230
But since I didn't provide any, the cat
program sits there waiting for input.

46
00:02:38,090 --> 00:02:41,770
I don't want to use this right now,
so I'm going to stop the cat program.

47
00:02:41,770 --> 00:02:46,520
To do this, I hold down the Ctrl key
on my keyboard and press the C key.

48
00:02:46,520 --> 00:02:50,580
This special key combination sends
a signal to the program telling it that I

49
00:02:50,580 --> 00:02:51,170
want to quit.

50
00:02:52,500 --> 00:02:55,070
Any time a terminal program
appears to be stuck or

51
00:02:55,070 --> 00:03:00,020
isn't doing what you want, you can
press Ctrl+C to send it this signal.

52
00:03:00,020 --> 00:03:03,470
Most of the time, the program will quit
and return you to the shell prompt, so

53
00:03:03,470 --> 00:03:05,530
you can run another command.

54
00:03:05,530 --> 00:03:08,250
By the way, you may be wondering
what's up with these crazy command

55
00:03:08,250 --> 00:03:10,550
names like ls and cat.

56
00:03:10,550 --> 00:03:11,950
When you're working in the terminal,

57
00:03:11,950 --> 00:03:14,040
there are certain commands
you'll be using a lot.

58
00:03:15,040 --> 00:03:17,820
You don't wanna have to type
the word list over and over, so

59
00:03:17,820 --> 00:03:20,800
the command name is abbreviated to ls.

60
00:03:20,800 --> 00:03:22,970
You don't wanna type
concatenated all the time, so

61
00:03:22,970 --> 00:03:25,080
the name is shortened to cat, and so on.

62
00:03:26,230 --> 00:03:29,830
The abbreviations take a little extra
time when you're learning the commands.

63
00:03:29,830 --> 00:03:33,350
But believe me, they'll save you
some typing in the long run.

64
00:03:33,350 --> 00:03:35,300
Let me run one more program, clear.

65
00:03:36,870 --> 00:03:39,930
The clear program clears output
from the terminal screen,

66
00:03:39,930 --> 00:03:42,020
moving the prompt up to the top.

67
00:03:42,020 --> 00:03:45,280
By default, Bash shell also
supports a keyboard shortcut that

68
00:03:45,280 --> 00:03:48,930
does the same thing,
just hold the Ctrl key and press L.

69
00:03:50,240 --> 00:03:52,750
You don't have to remember
this key combination,

70
00:03:52,750 --> 00:03:55,300
it's not as important as Ctrl+C.

71
00:03:55,300 --> 00:03:57,690
But if you see me clear
the screen during this course,

72
00:03:57,690 --> 00:04:00,930
you'll know I did it by pressing Ctrl+L.

73
00:04:00,930 --> 00:04:04,120
Before we move on, I should point out
a couple more aspects of the prompt.

74
00:04:05,260 --> 00:04:08,488
This prompt shows the name of
the current user, treehouse.

75
00:04:10,627 --> 00:04:16,690
Then it shows the directory or folder that
we're in, ~/workspace, or just workspace.

76
00:04:17,780 --> 00:04:19,880
I can change to a different directory, and

77
00:04:19,880 --> 00:04:23,640
the directory name will be updated
when the new prompt is shown.

78
00:04:23,640 --> 00:04:27,540
We'll talk more about directories
and the cd command later.

79
00:04:27,540 --> 00:04:28,610
As I mentioned before,

80
00:04:28,610 --> 00:04:32,450
the end of the prompt is usually marked
with a dollar sign for normal users.

81
00:04:32,450 --> 00:04:36,390
This could be changed, but
it's conventional to use a dollar sign.

82
00:04:36,390 --> 00:04:37,860
The prompt is customizable, so

83
00:04:37,860 --> 00:04:41,070
don't worry too much if the prompt
on your system shows different info.

84
00:04:42,390 --> 00:04:44,670
Now you know how to enter
commands in the shell.

85
00:04:44,670 --> 00:04:47,900
Up next, we'll look at ways to change
the behavior of those commands.