- So we have seen men, we have seen pinfo,
and do you believe it? There's more.
So what else is there?
Let me show you an overview of help systems.
Man is the primary source for getting information,
and I would always advise use man, not Google.
The thing with Google is that often you find
outdated information or information
that was written for a different distribution.
Don't use it, man has been developed for your distribution,
so it should always be accurate.
We have seen pinfo, and earlier we have already seen
command --help, which provides short usage information.
What I would advise, if you already know the command,
and you are just looking for the appropriate option,
use command --help.
If you don't know the command,
and you want to investigate what it is doing, use man.
Apart from that, there is /usr/share/doc.
/usr/share/doc contains additional help for some commands.
In some cases, it is very useful.
In other cases, it is relatively useless,
and it's only giving you some legal stuff.
And then there is tldr,
which is relatively new, and it shows commands use examples.
Let's have a look at these last two,
because we haven't seen them yet.
Of these additional help systems,
we have already seen man, pinfo, and command --help.
Let's have a quick look at /usr/share/doc.
So what do we find in /usr/share/doc?
Well, we find subdirectories.
Subdirectories for additional packages and programs.
So, if I am picking out anything random, lzo for instance,
what is lzo? I have no idea.
And the thing is that if you look at the contents
of this /usr/share/doc,
it's not going to help us very much either.
These are just some mandatory files
with authors, news, and thanks.
The news typically will show you, well,
news about the package. Use get if you want to read it,
and there you can see it's a change log.
Now, is there anything else that we can check right here?
Let me see. Let's have a look at dos2unix, for instance.
And what do we see in dos2unix?
Hey, that's an interesting one, we see a file
with the name htm, .htm.
ls -l, ls -l in this case is convenient
because it shows me file size. 34 kilobyte in an html file.
That means that it is very likely that this one
contains some useful additional documentation,
and that is the reason why I wanted to show you
this /usr/share/doc.
In some cases, it contains useful additional information.
And I would say, if you're desperate,
you really don't know how to use this command, check it out.
Maybe it contains something, no promises though.
The other command is tldr, let me type tldr,
and oh no, I'm getting tldr command not found.
Why is that? That is because it's relatively new.
Now, I can give it a try and use sudo dnf install tldr
to install the package
if it is available from the repositories.
And, oh boy on CentOS, it's not available at all.
How about Ubuntu?
On Ubuntu also, you will probably have to install it.
Sudo apt install tldr,
And there we go.
And we can see that on this Ubuntu system,
it was already available.
And the thing in this tldr is that tldr can help you
providing additional documentation.
The problem is that the additional documentation
must have been written.
So let me use tldr on ss, ss is for socket statistics,
and the idea is that if you have a valid entry,
you get command line usage.
But here I'm just getting no tldr entry,
and that is probably because this Ubuntu version
is pre release.
Don't rely on tldr too much,
but if it exists it can be very useful.
So go check it out, but continue and use man
as your primary source of information.