displaying files from directory

Question

I have a directory name called dir. It contain following files in order

I wrote following C program to display all the files from the directory dir

code :

#include <stdio.h>
#include <string.h>
#include <dirent.h>
int main (int argc, char *argv[])
{
    DIR *directory;
    struct dirent *file;     
    directory = opendir (argv[1]);
    if (directory != NULL){
        while (file = readdir (directory))
              printf("FILE : %s \n",file->d_name);

        (void) closedir (directory);
        }
   else
        printf("Not able to open the directory\n");
   return 0;
}

Above code give the actual output as

FILE : 14.07.2013 
FILE : 13.07.2013 
FILE : 17.07.2013 
FILE : . 
FILE : 15.07.2013 
FILE : .. 
FILE : 12.07.2013 
FILE : 16.07.2013

but i expected output in proper order like below

FILE : 12.07.2013 
FILE : 13.07.2013 
FILE : 14.07.2013 
FILE : 15.07.2013 
FILE : 16.07.2013 
FILE : 17.07.2013

When i directly see the files in directory it arranges & diplaying the files in proper order.

Then why above C code not reading file in proper order, i mean randomly reading the file.

Working environment : Linux(ubuntu12.04), gcc compiler

Thanks

score 3 · Accepted Answer · answered Jul 17 '13 at 18:11

3

It's not randomly reading the files, it's just reading the directory listing in the order it's stored in the directory file itself. When you "directly see the files in directory", I presume that means you're using ls, but ls is sorting the results before output. If you want matching output you need to do the same.

answered Jul 17 '13 at 18:11

Carl Norum

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.. and `readdir()` doesn't exclude file names starting with `.` so you see `.` and `..` like in `ls -a` – Ingo Leonhardt Jul 17 '13 at 18:15
Thanks for your response.@carl : you mentioned "it's stored in the directory file itself" what it mean. – sujin Jul 17 '13 at 18:17
1

@sujin, directories are files, too. They just happen to contain lists of references to other files instead of being an image or a text file or a database or something else. – Carl Norum Jul 17 '13 at 18:17
@CarlNorum : is there any command to list the files in order, which my code display. – sujin Jul 17 '13 at 18:19
You mean is there a way to sort them? Probably lots. If you want standard C, look into `qsort`. – Carl Norum Jul 17 '13 at 18:21
no. you mentioned "order it's stored in the directory file itself". so is there any standard command to see the order you mentioned. – sujin Jul 17 '13 at 18:23
1

Yes - `ls -1aU` should do it for your case. – Carl Norum Jul 17 '13 at 18:25
Shouldn't `.` and `..` always be the first 2 entries read with `readdir()`? How could other been moved before them? – ott-- Jul 17 '13 at 18:34
@ott--, filesystem implementation detail, I guess. – Carl Norum Jul 17 '13 at 18:35
@ott-- if the filesystem uses a directory format optimized for fast lookups (like ext[234] with `dir_index` enabled) the order of names in a directory has little or no relationship to the order of their creation, so `.` and `..` can be anywhere. – Jul 17 '13 at 19:26

displaying files from directory

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