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- In this video, we are
going to talk about man.

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What is man?

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Man is the System Programmers Manual.

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And you know, it goes all the
way back to the early 1970s

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when the first Unix
systems were introduced

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and the developers created
the man pages actually

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on a typewriter.

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And if you ever go to
Mountain View in California

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you can still see them in the
Museum of Computer Science.

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Very interesting.

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Nowadays, it's not printed pages anymore.

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It's an online system that you can use

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by accessing the man command.

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The man command is very important.

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You should make sure that you
are very familiar with it.

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And that is because the
man command is the main

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but not the only source

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for getting information
about Linux command usage.

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Now, the thing is that
Linux is open source

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and in open source, you have
people who do what they want.

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The result is that very
frequently in Linux

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you will see different
solutions for the main problem.

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But if one solution is really
better than the other ones

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it will become the dominant solution.

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And that is what has
happened with with man.

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So man is the main source

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for information about
Linux command line usage.

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And you use it to get information

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about commands,
configuration files and more.

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Before I show you all the
information on the next slide

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let me already give you an impression

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of what man is all about.

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So here we are.

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And let me, let me type man who am I.

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I'm starting with a simple command.

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And what do we see?

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We see a man page that
actually fits on one page.

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And there's not many of them
as you will discover later.

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So what do we see?

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First line, this is the header line.

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And isn't that surprising?

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Do you remember what I said

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about Linux being case sensitive?

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Well, from that perspective,
it's kind of weird

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that the first line is the header line

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and we see the command in uppercase.

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And that is so for all the items
that are documented in man.

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That's a tribute to history.

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The original man pages were
created on a typewriter

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and on the typewriter,
the author used uppercase

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for the command on the first line.

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Behind the command, who am
I we can see the number one.

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Number one is about the man section.

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Man is organized in sections

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and we should try to
understand these sections

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but we'll do that later.

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For now, let's have a quick glimpse

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of what we see right here.

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So we have name.

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That's the name of the command

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including a short summary of
what the command is used for.

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Now, we have the synopsis.

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The synopsis is the name

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of the command followed by option.

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Now look at the way,
how option is written.

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Option is written between square brackets.

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If in men output or in
help, output in general

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anything is between
square brackets that means

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that it is optional.

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Which means that you can use it.

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You don't have to use it.

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It's not mandatory.

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So you can use options

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and the options are listed right here.

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It's not very much in the who am I command

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as we have seen before.

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Behind the option, we have dot dot dot.

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Dot dot dot is a modifier of
what you see before the option.

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It means that you can
have multiple of them.

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So you can use who am I with one option

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or with many options.

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And then you get the additional
information, the author,

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the reporting books, the
copyright, and also the see also

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which is telling you that this
is not the real information.

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You should use the info command

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to get access to the real information.

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I'll tell you about that later.

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For now, I want to show
you another man page.

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And that is man, man.

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Oh, yes, man itself
has a man page as well.

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It's a little bit more complicated.

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And I want you to understand what we see.

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It starts with the synopsis

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and in the synopsis you can
see the different uses of man.

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So we can use man with man
options, which are optional

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which specific sections and pages

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in which section is optional to the page

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in which you can have multiple

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of them and multiple of
the preceding item as well.

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Wow, is that difficult to read?

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I think it is, but this
is the man page of man.

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And I would say

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if you wanna know more about
it, just continue reading.

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You will find the explanation
in the description.

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What you also need to know is

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that here we have different use cases.

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So you can use man minus lowercase
K, man minus uppercase K,

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minus F, minus L, minus w.

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And all of these are documented
further in the man page.

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Hey, this is an interesting one.

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We should explore this one as well.

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So minus w in lowercase,
as well as uppercase.

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What is this construction with
the pipe sign in the middle?

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Well, this construction with the pipe sign

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in the middle means that you
need to select one of them.

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You can't use both.

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So it's either minus lowercase w

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or minus uppercase w to do
whatever you want to do.

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You will also notice that this
minus w is sometimes written

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with curly braces around it.

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So man curly brace minus w pipe
minus w closing curly brace.

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It's exactly the same.

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Now, the reason that we are really here is

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because of the section numbers.

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Here, we have the sections.

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How should you see that?

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See it as chapters in a book

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and every chapter is
defining its own things.

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Here we have section number one, which is

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for executable programs or shell commands.

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Section number one.

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This is commands that you
can use as an ordinary user.

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There is section number eight.

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That's the other one
that is very important

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which is about sys admin commands.

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So what does that mean?

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That means if you see a man page

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with an eight in the header line

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that you better prepare your sudo session

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because what is documented

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in section number eight
requires sudo superpowers.

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And there is section number five

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which is about file
formats and conventions.

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Now, what is this file
formats and conventions?

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Well, very simple.

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That's about configuration files.

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One, five, and eight.

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These are the most important ones.

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And in case you want more
information about everything else

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have a look at what you see here.

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This is what is explaining
how man is actually used

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and how these placeholders and the options

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and all the different
alternatives are actually used.

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Let me use Q.

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Q to get out of here.

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Q for quit.

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Q for quit is a very generic Linux command

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to get out of surf.

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And let's get back to the slides

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because I have some more information

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about man on the next slide.

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So here is what is on the slide.

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So in a man page

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you will find a command summary.

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Command summary, it's showing
you how to use a command.

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And we have seen the items
between brackets are optional.

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And if you see curly braces, a pipe b

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you must choose and as discussed

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sometimes the curly braces are missing.

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And dot dot dot means

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that you may have more
of the preceding item.

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Now we have seen in the sections.

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That we have seen that section
one is for end user commands.

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Section eight is

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for administrator
commands or root commands.

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Anything that requires
you to type sudo in front.

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And then there is section five

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which is for configuration files.

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Many man pages have examples near the end.

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And that is pretty awesome.

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It makes working with Linux a lot easier

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especially if the command
is becoming more complex.

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You will see that simple commands
don't have these examples.

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More complex commands do.

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And otherwise they will have related items

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near the end as well.

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And that is convenient if you
are looking for a command.

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You were in a man page

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but it's just not the right command.

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Then you will have look
at the related items

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to find the actual command
that you needed to use.

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In man pages you can search.

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So slash some text will
search for some text.

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And you can use Q to
get out of the man page.

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Before we are moving
on one more small demo

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about these man pages.

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So this time I'm having
a look at man LV create.

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At this point, we totally do not care

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about the LV create command.

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The thing that I want to
show you here is the nice way

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how it is formatting all of its output.

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Like this highlighted line,
for instance, which is

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about the command line option
minus a or alternatively minus

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minus activate, and these

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or regardless which
one you are using, have

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a yes, a no, or an all yes,
separated by pipes again.

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So I'm using the space
bar to move forward.

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And there we go.

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We have some usage examples
about this lvcreate.

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Usage or examples.

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It's really basically the same.

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But lvcreate is so big a command

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that they included the separate
section with the name usage.

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And look at that.

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We even have some advanced usage.

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Just giving you an impression

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of how rich this environment is.

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And there we go, the examples.

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Examples is what you find

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in more complex man pages.

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And if you go further,
what else do we have?

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We have see also.

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If lvcreate happens to be
not exactly what you need

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then see also is giving an
overview of related commands.

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You might find what you
need right in there.

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Okay, now I'm going to use the G key.

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G for go all the way to the
top, because I want to show you

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and look at the lower left corner.

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I want to show you how you can search

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for text in a man page.

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So I'm using slash
write, which will search

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for the text write in the man page.

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And there you see,

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that the first occurrence
of the word is highlighted.

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If you need to see the next press N

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and N and N until you found
what you were looking for

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and once you are ready
press Q to get out of here.

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That's how you use man.

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Let's continue with the next topic.