1
00:00:00,000 --> 00:00:01,949
[No audio]

2
00:00:01,949 --> 00:00:05,789
Do While scripts. Do while scripts are

3
00:00:05,789 --> 00:00:09,299
very similar to for loop scripts.

4
00:00:09,299 --> 00:00:11,279
[No audio]

5
00:00:11,279 --> 00:00:13,979
The do while script or statement

6
00:00:13,979 --> 00:00:17,249
continually executes a block of

7
00:00:17,249 --> 00:00:19,679
statements while a particular condition

8
00:00:19,679 --> 00:00:23,219
is true or met. For example, if you are

9
00:00:23,219 --> 00:00:25,049
running a script and you create it in a

10
00:00:25,049 --> 00:00:29,249
loop, it will run until a certain

11
00:00:29,549 --> 00:00:32,609
variable is met. For example, if you

12
00:00:32,639 --> 00:00:35,099
have, if you want to run the script

13
00:00:35,129 --> 00:00:41,099
until August 2015, to 2pm, then you

14
00:00:41,099 --> 00:00:44,609
will define that in do while script. And

15
00:00:44,639 --> 00:00:47,369
a lot of times, the scripts or the

16
00:00:47,399 --> 00:00:50,459
daemons, the process that never dies, that

17
00:00:50,459 --> 00:00:52,049
keep running and running and running,

18
00:00:52,289 --> 00:00:54,659
they always have do while scripts

19
00:00:54,659 --> 00:00:57,959
because they are running continuously

20
00:00:58,229 --> 00:01:05,069
until a certain condition is met. So for

21
00:01:05,069 --> 00:01:07,979
example, run a script until 2pm. As soon

22
00:01:07,979 --> 00:01:11,039
as the 2pm hits, you are done, exit out.

23
00:01:12,029 --> 00:01:16,676
While, condition, do, command1, command2,

24
00:01:16,676 --> 00:01:18,749
command3. And once all these

25
00:01:18,749 --> 00:01:21,299
commands are done, and the condition is

26
00:01:21,299 --> 00:01:25,739
done, then you are done. You are done

27
00:01:25,769 --> 00:01:28,859
with your script. So let's look at our

28
00:01:28,859 --> 00:01:33,648
Linux machine, and let's try out a do while script.

29
00:01:33,648 --> 00:01:36,935
[No audio]

30
00:01:36,935 --> 00:01:39,029
Let's clear the screen, where we

31
00:01:39,029 --> 00:01:41,249
are, we are in myscripts directory, which

32
00:01:41,249 --> 00:01:45,089
is this directory we want to be in, and

33
00:01:45,389 --> 00:01:47,129
this time we're going to create a new

34
00:01:47,129 --> 00:01:49,049
script, and we are going to call it

35
00:01:49,439 --> 00:01:52,534
script-dowhile.

36
00:01:53,534 --> 00:01:56,339
Again, it's just the

37
00:01:56,339 --> 00:01:57,389
name I'm picking, you could pick

38
00:01:57,389 --> 00:02:00,689
anything you want. Hit enter, you are in

39
00:02:00,689 --> 00:02:03,959
vi mode, you hit insert, and you start

40
00:02:03,959 --> 00:02:05,579
typing. What's the first thing that you

41
00:02:05,579 --> 00:02:11,399
type, you type hash, bang, /bin/bash, which

42
00:02:11,399 --> 00:02:15,119
defines your shell environment. And if

43
00:02:15,119 --> 00:02:17,399
you wanted to put a comment, you could

44
00:02:17,399 --> 00:02:26,832
say, This script is created by Imran Afzal

45
00:02:26,832 --> 00:02:32,669
on 2018. Yeah, that's fine. And if you

46
00:02:32,669 --> 00:02:34,349
want to put a description of the script,

47
00:02:34,349 --> 00:02:36,269
you could do that. But let's get into

48
00:02:36,269 --> 00:02:38,789
the script. I have already written down

49
00:02:38,789 --> 00:02:41,099
a script, and I'm just gonna go in and

50
00:02:41,099 --> 00:02:43,019
copy it, there are two scripts in my

51
00:02:43,019 --> 00:02:45,599
handout, I'm going to take the second

52
00:02:45,599 --> 00:02:47,129
one, I want you to do the first one

53
00:02:47,129 --> 00:02:49,349
yourself, I'm just going to copy it, and

54
00:02:49,349 --> 00:02:52,559
I'm going to paste it real quick. Let's

55
00:02:52,559 --> 00:02:55,079
see what the script does. The script is

56
00:02:55,079 --> 00:02:57,359
doing, of course, the first one is

57
00:02:57,389 --> 00:03:00,089
defining the shell which we already

58
00:03:00,089 --> 00:03:01,949
have. So we're going to take it out by

59
00:03:02,009 --> 00:03:05,969
hitting dd, and then it's telling us

60
00:03:05,969 --> 00:03:09,149
that the count is zero, the number is

61
00:03:09,149 --> 00:03:13,619
10. While the count is less than 10, do

62
00:03:14,219 --> 00:03:16,829
echo number of seconds left to stop this

63
00:03:16,829 --> 00:03:19,589
process. And the process is the variable

64
00:03:20,009 --> 00:03:21,299
which is $1.

65
00:03:21,299 --> 00:03:28,980
[No audio]

66
00:03:28,980 --> 00:03:32,670
And echo, it's just an empty space, empty line,

67
00:03:32,820 --> 00:03:37,800
sleep, sleep is a command that will wait

68
00:03:37,800 --> 00:03:39,810
for the number of seconds that is

69
00:03:39,810 --> 00:03:44,070
defined after the sleep command, then it

70
00:03:44,070 --> 00:03:46,770
has a few number of expressions. These

71
00:03:46,770 --> 00:03:48,240
are the expressions you could get it

72
00:03:48,240 --> 00:03:51,330
anywhere online, I have that expression

73
00:03:51,330 --> 00:03:54,390
for a while that I tried out many times

74
00:03:54,390 --> 00:03:55,830
in my work environment, and works

75
00:03:55,830 --> 00:03:58,110
perfectly. And if you want to use it in

76
00:03:58,110 --> 00:04:00,120
your work environment you are more than

77
00:04:00,120 --> 00:04:02,430
welcome to do. So the next one is the

78
00:04:02,460 --> 00:04:04,980
echo, and then it says echo $1,

79
00:04:04,980 --> 00:04:09,690
process is stopped!!!!, and echo again, it is

80
00:04:09,690 --> 00:04:12,900
telling it that it's giving an empty

81
00:04:12,900 --> 00:04:15,960
line. So let's run the script and let's

82
00:04:15,960 --> 00:04:20,220
see what it does. Give it an executable

83
00:04:20,220 --> 00:04:25,200
permissions. It says 10 seconds left to

84
00:04:25,200 --> 00:04:33,990
stop this process, 9, 8, 7, 6, 5, 4, 3, 2, 1, and done,

85
00:04:33,990 --> 00:04:37,830
process is stopped!!!! You see that? So

86
00:04:37,830 --> 00:04:42,480
these do while scripts are created for a

87
00:04:42,480 --> 00:04:49,500
certain value or certain time to be met.

88
00:04:49,890 --> 00:04:53,430
And once that variable is met, they will

89
00:04:53,460 --> 00:04:57,450
stop the process and exit out of it. I

90
00:04:57,450 --> 00:04:59,580
want you to create a new script in

91
00:04:59,580 --> 00:05:02,130
you're in environment, and this is the

92
00:05:02,130 --> 00:05:04,380
script. Again, this is also in the

93
00:05:04,380 --> 00:05:06,900
handouts. You could copy and paste this

94
00:05:06,900 --> 00:05:09,150
script, create a new script, and run it.

95
00:05:09,630 --> 00:05:13,380
You could also be my guest to go online

96
00:05:13,650 --> 00:05:16,800
and just type do while script examples

97
00:05:16,800 --> 00:05:19,500
there are tons and tons of do while

98
00:05:19,680 --> 00:05:22,920
scripts that you could try and get, get

99
00:05:22,920 --> 00:05:28,560
a low exposure to do while scripts. I'm

100
00:05:28,560 --> 00:05:30,600
sure by the time you will run at least

101
00:05:30,600 --> 00:05:32,940
five or six scripts you know exactly

102
00:05:33,210 --> 00:05:35,946
what this statement do.

103
00:05:35,946 --> 00:05:40,139
[No audio]