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Absolute Paths

4:56 with Jay McGavren

The paths we saw in the previous video were relative paths. A relative path that works in one directory may not work if you change to a different directory. In this video, we're going to look at absolute paths, which stay the same no matter what directory you're in.

  • If I change up to the parent directory enough times, eventually I'll reach a directory where I can't go any further.
    • This is the root directory. If you imagine the file system like a tree, with directories as branches, the root directory would be the base that all the other branches spring out of.
    • The root directory doesn't have a name.
    • Its path is just a single slash (/).
treehouse:~/workspace$ pwd
/home/treehouse/workspace
treehouse:~/workspace$ cd ..
treehouse:~$ pwd
/home/treehouse
treehouse:~$ cd ..
treehouse:/home$ pwd
/home
treehouse:/home$ cd ..
treehouse:/$ pwd
/
treehouse:/$ cd ..
treehouse:/$ pwd
/
  • Now let me show you a simpler way to get to the root directory.
    • We started out in the home/treehouse/workspace directory. Let me change back there: cd home/treehouse/workspace/
    • Instead of typing cd .. a bunch of times, I can type cd / to jump to the root directory: cd /
    • This works no matter what directory I'm in.
treehouse:/$ cd home/treehouse/workspace/
treehouse:~/workspace$ cd /
treehouse:/$ pwd
/
treehouse:/$ cd home/treehouse/
treehouse:~$ cd /
treehouse:/$ pwd
/
  • An absolute path is one that starts at the root directory.
  • A slash by itself is the simplest absolute path; it takes you straight to the root directory, no matter where you are on the file system.
    • Let's find a different directory to go to: ls
    • I'll change to this bin directory: cd bin/
    • And now I'll change back to the root directory: cd /
  • Absolute paths start at the root directory, but like other paths, you can then join other directory names onto them.
    • Suppose I was in the bin directory: cd bin/
    • And I wanted to change to the dev directory.
    • I couldn't do it with a relative path, because it assumes I mean a dev directory that exists within the bin directory: cd dev
    • But there is a dev directory within the root directory. So if I start my path with the root directory, it will work: cd /dev
    • Suppose I now want to change to the etc directory within the root directory. I don't have to change back to the root directory and then change to etc, I can just cd /etc to jump directly there.
treehouse:/$ cd /
treehouse:/$ cd bin/
treehouse:/bin$ cd dev
bash: cd: dev: No such file or directory
treehouse:/bin$ cd /dev
treehouse:/dev$ cd /etc
treehouse:/etc$
  • Now let's try a longer absolute path.
    • We started out in the home/treehouse/workspace directory. Let's see if we can use an absolute path to get back there, starting from the etc directory.
    • The home directory is within the root directory, so we start with the root: /home/treehouse/workspace
    • We're taken straight there: pwd
    • I can also jump straight back to the /etc directory, or any other directory, by using its absolute path: cd /etc 
treehouse:/etc$ cd /home/treehouse/workspace
treehouse:~/workspace$ pwd
/home/treehouse/workspace
treehouse:~/workspace$ cd /etc
treehouse:/etc$
  • Absolute paths work with files, too.
    • Let's suppose I want to print that Starbunks menu again, but I don't want to leave the /etc directory.
    • I can type the cat command name: cat...
    • Then I can type the absolute path of the menu.txt file.
    • It's a long path, so I'm going to use tab completion to help me remember all the directory names.
    • [hom, Tab, tr, Tab, wo, Tab, mal, Tab, st, Tab, men, Tab.]
    • There it is, the complete absolute path of the menu.txt file, starting at the root directory.
    • And when I run the command, the cat program finds the file and prints its contents.
    • All without leaving the /etc directory: pwd 
treehouse:/etc$ cat /home/treehouse/workspace/mall/starbunks/menu.txt
Venti Iced Mocha Soy Latte (with Whip): $29.99
Grande Hot Americano: $34.99
Tall Hot Chocolate: $24.99
treehouse:/etc$ pwd
/etc
  • Absolute paths are a bit less convenient than relative paths.
    • If you're currently in or near the same directory as a file, you can use the file's absolute path to access it.
    • But it would probably be more convenient to use a relative path.
  • But when you're nowhere near the file or directory you want to access, or if you don't even know where you are relative to your target, you should use its absolute path. Absolute paths eliminate all confusion about where a file or directory is within the file system.

The paths we saw in the previous video were relative paths. 0:00
A relative path that works in one directory may not work if you change to 0:03
a different directory. 0:07
In this video, we're going to look at absolute paths which stay the same no 0:09
matter what directory you're in. 0:12
If I change up to the parent directory enough times, 0:15
eventually I'll reach a directory where I can't go any further. 0:17
So I'll say cd dot dot. 0:20
That will change me to my home directory. 0:22
CD dot, dot again. 0:25
That will change me to the slash home directory. 0:28
And CD dot dot one more time. 0:31
And this changes me to yet another directory. 0:37
If I try typing CD dot dot in this directory, it won't go anywhere. 0:40
If you imagine the file system like a tree with directories as branches, 0:45
the root directory would be the base that all the other branches spring out of. 0:49
The root directory doesn't have a name. 0:53
Its path is just a single slash. 0:56
Now, let me show you a simpler way to get to the root directory. 0:58
We started out in the home slash treehouse slash workspace directory. 1:03
Let me change back there. 1:07
CD, and I'll use tab completion here, home slash treehouse slash workspace. 1:08
Instead of typing CD dot dot, a bunch of times, 1:16
I can type CD slash to jump straight to the root directory. 1:19
This works no matter what directory I'm in. 1:23
Let's change to the home slash treehouse directory. 1:27
CD home slash treehouse. 1:29
Without the workspace directory on the end. 1:31
Once again, cd slash will take me back to the root directory. 1:36
An absolute path is one that starts at the root directory. 1:42
A slash by itself is the simplest absolute path. 1:47
It takes you straight to the root directory, 1:50
no matter where you are on the file system. 1:52
Let's find a different directory to go to. 1:55
I'll run ls to list the contents of this root directory. 1:58
And I'll change to this bin directory, cd bin slash. 2:01
Again, the slash is optional. 2:06
And now, I'll change back to the brief directory, cd slash. 2:09
Absolute paths start at the route directory. 2:11
But like other paths, you can then join other directory names onto them. 2:15
So suppose I was in the bin directory. 2:20
Cd bin. 2:22
And I want to change to the dev directory. 2:23
I couldn't do it with a relative path because it assumes I mean a dev directory 2:26
that exists within the bin directory. 2:30
But there is a dev directory within the root directory. 2:34
So if I start my path with the root directory, it will work. 2:37
Cd slash dev. 2:40
Suppose I now want to change to the etc directory within the root directory. 2:43
I don't have to change back to the root directory and then change to etc. 2:47
I can just cd slash etc to jump directly there. 2:51
Now, let's try a longer absolute path. 2:56
We started out in the home slash treehouse slash workspace directory. 2:58
Let's see if we can use an absolute path to get back there, 3:03
starting from the etc directory. 3:05
The home directory is within the root directory. 3:08
So we start with the root, slash, then type home slash treehouse. 3:10
And I'll start using tab completion now. 3:16
And workspace. 3:18
We're taken straight there. 3:21
I can also jump straight back to the etc directory, or any other directory, 3:24
by using it's absolute path, cd slash etc. 3:28
Absolute paths work with files, too. 3:32
Let's suppose I wanna print that starbunks menu again, but 3:35
I don't wanna leave the slash etc directory. 3:38
I can type the cat command name, and 3:40
then I can type the absolute path of the menu dot txt file. 3:43
It's a long path, so 3:46
I'm going to use tab completion to help me remember all the directory names. 3:47
I'm gonna start with slash h-o-m tab. 3:51
completes the home directory name. 3:55
T-r, that completes treehouse. 3:57
W-o completes workspace. 4:00
M-a-l completes mall. 4:04
S-t-tab completes starbunks. 4:06
And m-e-n-tab completes menu dot text. 4:09
There it is, the complete absolute path of the menu dot text files, 4:14
starting at the root directory. 4:17
And when I run the command, the program finds the file and prints its contents, 4:19
all without leaving the etc directory. 4:24
Absolute paths are bit less convenient than relative paths. 4:27
If you're currently in or near the same directory as a file, 4:31
you can use the file's absolute path to access it. 4:34
But it would probably be more convenient to use a relative path. 4:37
But when you're nowhere near the file or directory you want to access, 4:41
or if you don't even know where you are relative to your target, 4:44
you should use its absolute path. 4:48
Absolute paths eliminate all confusion about where a file or 4:50
a directory is within the file system. 4:53

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