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- So we have seen men, we have seen pinfo,

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and do you believe it? There's more.

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So what else is there?

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Let me show you an
overview of help systems.

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Man is the primary source
for getting information,

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and I would always advise
use man, not Google.

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The thing with Google
is that often you find

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outdated information or information

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that was written for a
different distribution.

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Don't use it, man has been
developed for your distribution,

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so it should always be accurate.

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We have seen pinfo, and
earlier we have already seen

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command --help, which provides
short usage information.

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What I would advise, if you
already know the command,

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and you are just looking
for the appropriate option,

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use command --help.

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If you don't know the command,

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and you want to investigate
what it is doing, use man.

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Apart from that, there is /usr/share/doc.

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/usr/share/doc contains
additional help for some commands.

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In some cases, it is very useful.

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In other cases, it is relatively useless,

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and it's only giving you some legal stuff.

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And then there is tldr,

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which is relatively new, and
it shows commands use examples.

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Let's have a look at these last two,

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because we haven't seen them yet.

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Of these additional help systems,

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we have already seen man,
pinfo, and command --help.

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Let's have a quick look at /usr/share/doc.

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So what do we find in /usr/share/doc?

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Well, we find subdirectories.

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Subdirectories for additional
packages and programs.

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So, if I am picking out anything
random, lzo for instance,

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what is lzo? I have no idea.

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And the thing is that if
you look at the contents

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of this /usr/share/doc,

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it's not going to help
us very much either.

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These are just some mandatory files

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with authors, news, and thanks.

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The news typically will show you, well,

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news about the package. Use
get if you want to read it,

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and there you can see it's a change log.

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Now, is there anything else
that we can check right here?

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Let me see. Let's have a look
at dos2unix, for instance.

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And what do we see in dos2unix?

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Hey, that's an interesting
one, we see a file

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with the name htm, .htm.

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ls -l, ls -l in this case is convenient

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because it shows me file size.
34 kilobyte in an html file.

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That means that it is
very likely that this one

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contains some useful
additional documentation,

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and that is the reason
why I wanted to show you

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this /usr/share/doc.

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In some cases, it contains
useful additional information.

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And I would say, if you're desperate,

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you really don't know how to
use this command, check it out.

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Maybe it contains something,
no promises though.

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The other command is
tldr, let me type tldr,

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and oh no, I'm getting
tldr command not found.

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Why is that? That is
because it's relatively new.

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Now, I can give it a try and
use sudo dnf install tldr

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to install the package

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if it is available from the repositories.

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And, oh boy on CentOS,
it's not available at all.

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How about Ubuntu?

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On Ubuntu also, you will
probably have to install it.

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Sudo apt install tldr,

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And there we go.

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And we can see that on this Ubuntu system,

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it was already available.

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And the thing in this tldr
is that tldr can help you

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providing additional documentation.

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The problem is that the
additional documentation

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must have been written.

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So let me use tldr on ss,
ss is for socket statistics,

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and the idea is that if
you have a valid entry,

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you get command line usage.

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But here I'm just getting no tldr entry,

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and that is probably
because this Ubuntu version

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is pre release.

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Don't rely on tldr too much,

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but if it exists it can be very useful.

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So go check it out, but
continue and use man

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as your primary source of information.