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- Okay, the next thing
that we should talk about,

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which is related to
files is using wildcards,

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also known as globbing.

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So, most file-oriented commands
support using wildcards,

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as in ls a*, which is showing all files

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that have a name starting
with an a, or ls a?*.

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The question mark stands
for one single character

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one single character, any character,

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and the star is an unlimited number

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of unspecified characters.

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So, this will show you all files that have

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a name of at least two characters.

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Then, we have ls a and then [nm].

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The nm between square
bracket means either or,

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so either an m or an n.

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And what do you think of ls a[a-e],

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for anything between the a and the e.

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Also useful, is that many commands

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also support working
with groups and ranges,

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as in touch file{1..100}.

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What is that doing?

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That is creating 100 files
in one single command.

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Or what do you think of
mkdir /data/{sales,account}

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which creates two directories in one.

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Let me demonstrate this.

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In order to demonstrate, I'm
getting into the etc directory

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and in the etc directory I'm using ls b*.

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So what do we see?

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We see that it's showing files

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that have a name starting with a b,

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but then something weird is happening.

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It's also showing matching directory names

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and for matching directory names,

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it shows all the files it
found in the directory.

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Now, that is exactly this
thing that I just talked about.

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If you use ls -d b*,

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then we see directory names
instead of directory contents.

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So that's probably so much better.

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Now let's use ls -d b*.?.

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Now, what is that?

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Well, let's try to understand ls b*.

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The star is for any character,
but then there is a dot.

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That means that we need a
dot in the name of the file.

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And then there is a question mark,

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which means that behind the dot

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we need one single character.

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And that is why we see
bash_completion.d and binfnt.d

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because these are the only
ones that have one character

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after the dot.

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So let's have a look at another example,

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ls [ab]???, and what is that showing, huh?

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It is showing files.

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And do these files match the pattern?

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00:03:01,890 --> 00:03:03,810
Hey, everybody,

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take a second to think about
what is happening here.

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You know what is happening?

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This is happening. Let's do ls -d.

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You remember what ls is doing

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when it finds the directory
that matches the pattern?

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It doesn't show the name of the directory.

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It shows the contents of the directory.

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And if we put a -d in front of it,

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then we can see that it actually
did what we asked it to do.

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ls -d [ab] plus ??? is looking for

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items that have a name
consisting of four letters

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starting with an a or a b.

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The only matching item
is alsa and without a -d,

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we see the contents of this alsa thing,

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and not really what we were looking for.

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As you can see, the output of ls

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sometimes is pretty confusing.

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Now, let me use ls [a-e]*,

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which is an easy one,

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as long as we don't forget to use the -d.

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00:04:02,700 --> 00:04:04,890
Hey, that's also something
we haven't seen before.

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I'm using the -d to the end.

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Can we do that? Yes, we can.

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Linux is a pretty
flexible operating system

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and command line options
can often be specified

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on the end of the command line as well,

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as we can see right here.

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Now, let's also talk about these ranges,

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and in order to do so, I'm
going back to my home directory.

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I am using touch file one up to many.

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Should I do that many?

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No, Let me just make the
point and let me use 100.

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And there we can see that it
easily created 100 empty files.

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Use any number that you
want, but be careful.

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00:04:46,680 --> 00:04:51,000
And maybe you wanna use rm
after it to removed that.

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I'm not sure if I should
be talking about it

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because we haven't talked
about rm yet, but rm is remove.

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And in this case, I think
it's useful to do that.

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And what do you think of mkdir?

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00:05:02,395 --> 00:05:06,783
Mkdir /data/{sales,account}.

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Now, this is an interesting one

96
00:05:10,920 --> 00:05:13,350
and you should know, everybody,
that every now and then

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I like to show you things that go wrong.

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And as you can see, this is going wrong.

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Why is it going wrong?

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00:05:20,580 --> 00:05:23,970
Well, not for one, but
even for two reasons.

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Reason number one is that it is trying

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to create a complete directory
path and we cannot do that.

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00:05:31,200 --> 00:05:32,623
The error message that I'm getting here

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00:05:32,623 --> 00:05:35,640
is that it is trying to
create directory sales

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00:05:35,640 --> 00:05:39,630
in the directory data but
directory data does not exist.

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00:05:39,630 --> 00:05:41,433
So, let me modify the command.

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Notice again that my cursor

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is at the end of the command line.

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I'm using control a to move my cursor

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to the start of the command line

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so that I can put a -p behind.

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Why am I doing that?

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I can do -p at the end
of the command line.

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Yeah, I know, but for
some reason I like it

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if my options come
directly after the command,

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and there we go and uh-oh,

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different error message,
permission denied.

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Of course we get a permission denied.

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We need sudo if you want to write

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into the root of the file system

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but with this command,
it should be working

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after we enter, of
course, the sudo password.

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There we go.

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And if I use ls /data, then we can see,

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and this time I wanted to see that

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we can see the content
of the /data directly

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containing account and sales,

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and that's exactly what I wanted.