Why does readdir() list ".." as one of the files?

Question

I am just not able to understand that why readdir() lists ".." as one of the files in the directory.
Following is my code snippet

while((dir = readdir(d)) != NULL)  
{  
    printf("%s \n", dir->d_name);  //It displayed .. once and rest of the time file names
}

`..` is the file that represents the parent directory, it is present in all directories. — mshildt, Oct 04 '13 at 00:53
@epicbrew I could be wrong, but I think it's usually present in the root as well; it is just a loop in the tree that points to itself. totally irrelevant, carry on. — mfsiega, Oct 04 '13 at 00:56

score 3 · Answer 1 · answered Oct 04 '13 at 00:57

3

.. is not actually a file it is a directory of the *nix file system. It represents the parent directory of the current directory. Similarly . is the representation of the current dirrectory. This is relevant for moving around the file tree and relative directory representations.

Take a look at this article on changing directories:

A cd .. tells your system to go up to the directory immediately above the one in which you are currently working

answered Oct 04 '13 at 00:57

CoderDake

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Actually a directory is a file in *nix. Everything is a file in *nix. See [here for more details](http://www.tldp.org/LDP/intro-linux/html/sect_03_01.html) – mshildt Oct 04 '13 at 01:03
@epicbrew: Yes, but directory *entries* are not files; rather, they refer to files. – Keith Thompson Oct 04 '13 at 01:13

mshildt · Accepted Answer · 2013-10-04T01:27:01.197

3

The . and .. represent the current and parent directory and are present in all directories (see footnote below). readdir() does not filter them out as they are valid entries within a directory. You can do the following to filter them out yourself.

while((dir = readdir(d)) != NULL)  
{
    if (strcmp(dir->d_name, ".") == 0 || strcmp(dir->d_name, "..") == 0) {
        continue;
    }
    printf("%s \n", dir->d_name);
}

_{Note: Technically, SUSv3 does not require that . and .. actually be present in all directories, but does require that the OS implementation correctly interpret them when encountered within a path.}

edited Oct 04 '13 at 01:27

answered Oct 04 '13 at 01:00

mshildt

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ya I already did strcmp seeing it somewhere on stackoverflow. But was not knowing the explanation of .. and . . Thanks for clarifying. – SPB Oct 04 '13 at 01:09

score 1 · Answer 3 · edited May 23 '17 at 12:29

1

It seems readdir() does not ignore '..' & '.'. So you have to filter the two files by yourself. This post might be helpful How to recursively list directories in C on LINUX

edited May 23 '17 at 12:29

Community

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answered Oct 04 '13 at 01:08

AlexInTown

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score 0 · Answer 4 · answered Oct 04 '13 at 06:24

0

readdir() reads the next directory entry. .. is a directory entry.

answered Oct 04 '13 at 06:24

alk

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Why does readdir() list ".." as one of the files?

4 Answers4