1
00:00:06,660 --> 00:00:10,260
- In this video, we are going
to explore the ls utility.

2
00:00:10,260 --> 00:00:12,960
So what is the ls utility?

3
00:00:12,960 --> 00:00:16,620
Well, you should start by using pwd to

4
00:00:16,620 --> 00:00:18,690
to find the name of the current directory

5
00:00:18,690 --> 00:00:21,270
and then you want to
investigate what's inside.

6
00:00:21,270 --> 00:00:23,490
And that is what ls is doing.

7
00:00:23,490 --> 00:00:26,140
ls is used to list files and directories

8
00:00:27,439 --> 00:00:30,360
and ls has a couple of
useful options like ls-a

9
00:00:30,360 --> 00:00:33,261
which will show hidden
files as well, or ls-L

10
00:00:33,261 --> 00:00:35,850
which provides a long listing

11
00:00:35,850 --> 00:00:39,090
providing many details about your files.

12
00:00:39,090 --> 00:00:40,980
Now you will notice,
and I will demonstrate

13
00:00:40,980 --> 00:00:43,800
that if you use ls -l on a directory

14
00:00:43,800 --> 00:00:45,840
now you see the contents
of that directory.

15
00:00:45,840 --> 00:00:49,140
If that's not what you
wanna see, use ls -ld

16
00:00:49,140 --> 00:00:50,550
that will show you the properties

17
00:00:50,550 --> 00:00:52,950
and not the contents of the directory.

18
00:00:52,950 --> 00:00:54,557
And there is ls -lrt

19
00:00:54,557 --> 00:00:57,780
which shows a time sorted list of files.

20
00:00:57,780 --> 00:00:59,940
That's a lot of options together

21
00:00:59,940 --> 00:01:02,190
but I'm putting them here
on the slide together

22
00:01:02,190 --> 00:01:06,000
because this is how normally
you would use a command.

23
00:01:06,000 --> 00:01:09,900
Ls -lrt is showing the last modified file

24
00:01:09,900 --> 00:01:11,280
last in the list.

25
00:01:11,280 --> 00:01:12,780
And that's the awesome solution.

26
00:01:12,780 --> 00:01:15,870
If you are trying to find
out what exactly has changed

27
00:01:15,870 --> 00:01:19,050
while you were doing a
certain manipulation.

28
00:01:19,050 --> 00:01:22,200
If you know which directory use ls -lrt

29
00:01:22,200 --> 00:01:25,563
and you will find the
last modified file last.

30
00:01:26,640 --> 00:01:27,573
Let me show you.

31
00:01:30,496 --> 00:01:31,329
All right.

32
00:01:31,329 --> 00:01:33,360
We have already seen ls -l.

33
00:01:33,360 --> 00:01:36,120
Here is ls -l again showing a list

34
00:01:36,120 --> 00:01:40,680
of directories in this case,
including their properties.

35
00:01:40,680 --> 00:01:44,370
Let me use CD without arguments
to get to my home directory.

36
00:01:44,370 --> 00:01:46,830
And in the home directory I'm using ls.

37
00:01:46,830 --> 00:01:50,760
This is what we see, just a
couple of directories mainly.

38
00:01:50,760 --> 00:01:52,500
If you use ls -a

39
00:01:52,500 --> 00:01:55,800
then we can see the hidden files as well.

40
00:01:55,800 --> 00:01:59,700
These are mostly configuration
files that are stored to

41
00:01:59,700 --> 00:02:02,640
determine how our environment is shaped.

42
00:02:02,640 --> 00:02:05,430
We'll explore these
configuration files later.

43
00:02:05,430 --> 00:02:08,460
I would like to show you ls -lrt.

44
00:02:08,460 --> 00:02:12,123
And I would like to show you
in the var log directory.

45
00:02:12,123 --> 00:02:15,570
Why? Because the var log
directory is a directory

46
00:02:15,570 --> 00:02:18,360
where different processes
are writing logs too.

47
00:02:18,360 --> 00:02:19,752
And if I wanna see which
log is the most used,

48
00:02:19,752 --> 00:02:24,752
well use ls -lrt, and you can
see the last modified file is

49
00:02:26,460 --> 00:02:30,270
mentioned last, which is messages 1405.

50
00:02:30,270 --> 00:02:33,185
Notice that this is
something for sent to us.

51
00:02:33,185 --> 00:02:36,388
If you do the same on Ubuntu,
shall we do it on Ubuntu?

52
00:02:36,388 --> 00:02:41,388
On Ubuntu, we go to var
log and I use ls -lrt.

53
00:02:43,320 --> 00:02:44,280
And what do we see?

54
00:02:44,280 --> 00:02:48,210
We see that on the Ubuntu
system, the name is syslog.

55
00:02:48,210 --> 00:02:51,570
It is also one of the biggest files,

56
00:02:51,570 --> 00:02:53,497
that also says something.

57
00:02:53,497 --> 00:02:55,500
One more thing that I want to show you

58
00:02:55,500 --> 00:02:58,410
and that is ls /etc or

59
00:02:58,410 --> 00:03:00,874
ls -l /etc.

60
00:03:00,874 --> 00:03:02,490
What is that doing?

61
00:03:02,490 --> 00:03:06,180
This is showing me contents
of the etc directory.

62
00:03:06,180 --> 00:03:07,860
Now, what if I don't want

63
00:03:07,860 --> 00:03:10,020
to see contents of the etc directory

64
00:03:10,020 --> 00:03:12,240
but just the properties of the directory.

65
00:03:12,240 --> 00:03:16,643
While in that case, I'm
adding a d, ls -ld /etc

66
00:03:16,643 --> 00:03:20,400
and now we can see the
properties of the directory

67
00:03:20,400 --> 00:03:23,970
and this ls -ld is going
to be very important,

68
00:03:23,970 --> 00:03:26,520
once you are going to manage permissions

69
00:03:26,520 --> 00:03:30,150
because permissions are
set often on directories.

70
00:03:30,150 --> 00:03:32,190
And if you want to see
the current settings,

71
00:03:32,190 --> 00:03:35,223
ls -ld on the directory will help you.