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Before I start, I'm gonna make sure
that I'm in my workspace directory.

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In the shell there are a variety of
symbols that have special meanings.

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We've already seen a couple
special symbols, dot and dot-dot,

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which are used to indicate the current and
parent directories.

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This video will look at those
symbols a little closer.

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We'll also look at the tilde symbol,

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which represents the user
account's home directory.

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Dot indicates the current directory.

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It may not seem that useful at first.

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Cd dot just changes to the same directory.

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You can use dot in the paths of files,
like cat ./bird.txt.

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But cat bird.txt does the same thing.

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It takes two fewer keystrokes.

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There are a few situations in
which dot is very useful, however.

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One is in running executable programs.

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Let me change to a directory where
I have an executable stored,

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cd offices/web_agency/mcgavren/.

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Let me list the files that are here.

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Here I have an executable
file named hello.sh.

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The sh is short for shell script.

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If you come from Windows,

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you're probably used to executable
files all ending in .exe.

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But on a Linux system like this one,

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executable files can have
any extension you want.

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On Unix-like systems, as a safety feature,

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you can't run an executable
file just by typing its name.

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You have to provide the executable's
name as part of a path.

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Using only what we've learned so
far, that would mean you have to

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change to the parent directory and
then type the name of the directory that

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contains the executable, a slash,
and the name of the executable file.

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But that's a pain if you're already in
the same directory as the executable.

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So you can form a path by using dot to
represent the current directory, a slash,

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and the name of the executable,
./hello.sh.

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Executable files are outside
the scope of this course,

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but if you'd like to know more about them,
see the teacher's notes.

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Another special symbol
we've seen is dot-dot,

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which represents the parent directory.

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We've already make extensive use of
cd dot-dot to change up a directory.

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You can also use dot-dot as
an argument for commands.

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For example,

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you can list then contents of the parent
directory by running ls dot-dot.

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You can also use dot-dot
as part of a path.

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Suppose we wanna change to the dentist
directory that's within the parent

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directory.

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We don't have to cd dot-dot and
then cd dentist.

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Instead, we can type cd ../dentist.

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The operating system will realize
this means the parent directory's

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dentist's subdirectory and
change directly to it.

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Now for a symbol we haven't
looked at thoroughly, the tilde.

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Like dot and dot-dot,
tilde is a reference to a directory,

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your user account's home directory.

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We can type cd ~ to go to that home
directory from anywhere on our system.

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You can see that the directory path in the
prompt changes to just a tilde character.

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That's not the real
path of this directory.

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To see the real path we can run pwd.

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You can see we're actually in
a directory named treehouse,

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which is in a directory called home,
which is the root directory.

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The name of the treehouse directory
matches the name of the user account we're

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logged in as.

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We can see that account name
if we run the whoami command.

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Each user account has its own
subdirectory under the home directory.

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Windows and Mac machines have equivalents
to the home directory at different paths.

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See the teacher's notes
if you'd like more info.

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If we run ls/home, we'll see there's
only the treehouse directory.

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That's because the treehouse account
is the only one that's been created on

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this system.

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If there were other users,
they'd have directories here too.

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So what's so
special about your home directory?

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Why is there a special shortcut for it?

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For ordinary users,

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the home directory is really the only one
on the system you should make changes to.

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The root directory is filled with
a dozen subdirectories or more.

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Each one of these directories
is filled with files that

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the operating system relies on to run.

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If you went around making
changes in these directories,

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you could render your
operating system unusable.

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Don't worry, Unix-like machines are set up
so that ordinary users simply get an error

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message if they try to make
changes in the root directory.

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Your home directory is the only
directory on your system that's

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specifically intended for
you to work in and make changes.

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And that's why there's a convenient
tilde shortcut to help you access it.

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Just like dot and dot-dot, you can use
tilde as part of a file or directory path.

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To change of the workspace
directory within your home folder,

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you can run cd ~/workspace/.

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This will work no matter
where you are on your system.

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For example, I could change to the /etc
directory within the root directory again.

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And if I run cd ~/workspace/, I'll be
taken directly to the workspace directory.

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You don't have to type out
the whole directory name.

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That's because tab completion works with
paths that start with tilde too, so I

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can say cd ~/wo tab and it'll complete the
name of the workspace directory for me.

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These are not absolute
paths that I'm showing you

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because the home directory is in
different places for different users.

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Still, using tilde does
work like an absolute path

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because it lets you reference files and

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subdirectories in your home directory
from anywhere on your system.

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Let's print out that Starbunks menu
one more time using a path relative

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to the home directory,
cat ~/workspace/mall/starbunks/menu.txt.