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Based on the question: How to make using command prompt less painful, what are the . and .. entries in the most voted answer? I see it when I do a dir command but it isn't visible to the user in the form of a file.

In case you dont know what I mean here's an example:

.
..
Su.exe
Sup.txt
SuperUser.COM
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4 Answers

up vote 30 down vote accepted

The . is the current directory, while .. signifies the parent directory. It makes things quicker at the command line as well so you don't need to type out full paths.

example:

go up 2 directories:

cd ..\..\

or on a UNIX based system, to run executable binaries in the current directory:

./program

A lot of UNIX scripts will also utilize . to represent the current directory, in order to scan for files for example (Perl):

#!/usr/bin/perl

opendir ( DIR, "." ) || die "Error opening current directory\n";
while( ($f = readdir(DIR))){
     print("$f\n");
}
closedir(DIR);

It is much more portable if you wish to move the script around to different directories or systems since a directory name is not hard-coded.

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It's little known, but the Windows command line extends this further. . = this directory .. = parent directory ... = parent's parent directory 3 dots is sometimes useful, much more than that and it's just too hard to deal with. –  salmonmoose Sep 9 '09 at 3:57
3  
3 dots does not work for me, using Vista –  Kevin Panko Sep 13 '09 at 0:21
    
nor me on Windows 7 64 bit RTM. Sounds like a myth to me. what's wrong with ..\.. anyway? –  AdamV May 26 '10 at 14:45
1  
@salmonmoose: Doesn't work for me on XP either. –  Simon P Stevens May 26 '10 at 14:59
1  
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The .. is used to navigate up the hierarchy of the file system. It's useful when you don't want to type a long path, or when writing a script/program that doesn't know where exactly it will be installed but it knows that ../media/ should hold all the images/videos/icons etc.

The single dot . is useful in linux where you want to run an executable in the current directory so you type ./a.out because the command shell by default doesn't search the current directory for executable files (for security reasons).

The single dot . is also used if you want to pass the current directory as an argument to a command.

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+1 for practical examples of use –  hyperslug Sep 8 '09 at 4:18
    
PowerShell also doesn't include . in the path list for searching executables. –  Joey Sep 8 '09 at 5:16
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The . is the current directory. You rarely need to use this; most commands will assume the current directory. The .. is the next level up; this is a rather useful shortcut. If you are in C:\foo\bar and you want to go to C:\foo\bar2 you can say

cd ..\bar2

and you will be in C:\foo\bar2. If you don't want to go to bar2 but only want to run C:\foo\bar.exe, then you can say

..\bar.exe

or ..\bar to run it without going back up to the parent directory. Of course, this is more useful when you are it represents a longer path that C:\foo (such as "C:\Users\Daniel\My Dropbox\".

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I find . to be quite useful at times, especially when copying or moving files to the current location (copy F:\*.foo .) or referring to it otherwise (start . opens the Explorer in the current directory, for example). –  Joey Sep 8 '09 at 5:17
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They stand for:

.

The current dir

..

Represents the parent dir

So if you have the executable "su.exe" in:

  • Your Path environment variable ( let say C:\MyExecutables\su.exe )
  • Your current dir
  • Your parent dir.

You could execute each one like this:

 su.exe

Executes the one in the Path

.\su.exe

Executes the one in the current dir

..\su.exe

Executes the one in the parent dir.

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