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At this point, we are about
ready to use the command line.

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Let's talk about a
couple of command line essentials.

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First thing to realize is
that Linux is case sensitive.

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So if you see lowercase, you type lowercase
because if you type uppercase it won't work.

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Also, you should realize that there is
an exception to any generic statement on Linux.

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Linux is open source, and because
of the decentralized development of different Linux

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components, there are always exceptions to
things that you consider to be true.

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Let's use an example of how to
quit an interactive interface. Sometimes you need

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control C, sometimes you need Q, sometimes
you need to type quit. It all

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depends on the discretion of the
open source developer behind the project.

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Now, while you are working with
commands, commands are often used with options.

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And these options can
be specified as long options.

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And long options start
with double hyphen. So Uname

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Help is printing help
for the Uname command.

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There's also short options, and short options start
with a single hyphen and they can be

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defined. So instead of using LS l r
minus T, you can also type LS lrt.

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Linux commands typically
have many options.

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If you want to know about these many options, you
use Help on any command to learn how to use it.

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Let me
show you.

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Let's use the LS command as an example.
If I type ls, then it works. If I

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type LS in uppercase, then I'm getting command
not found. But fortunately my shell is friendly enough

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to tell me that it knows about
similar commands, which is LS in all lowercase.

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Now how
about these options?

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LS Help is giving me a list of all of the options
and oh my goodness, that doesn't fit on the screen now does it?

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If I scroll up a little bit, I can see all
these options and as you can see, it's an entire Alphabet.

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Now if you look at the l
option, there we go. L uses a long

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listing format, and it's kind of funny,
L only exists as a short option.

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There are also options like
k for kibibytes that exist

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as a short option as
well as a long option.

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So LS l K will show
you kibibytes for all of the valves,

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but you can also use LS
l kibibytes to show the kibibytes value.

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For now, I
think that's enough.

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Let's explore some more commands
in the next couple of.