Using stat.h and listing directory contents...

smoothdogg00 · #1 13-Mar-2006, 18:58

Currently, I have a program that lists the contents of a directory. What I need to do (as I've sort of started) is to use the stat structure to print such things as date modified, etc. like the "ls" program does. My code is as follows:

CPP / C++ / C Code:

#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <dirent.h>
#include <string.h>

int main()
{
   char complete_filename[512];
   struct dirent **namelist;
   struct stat buf;
   int n = scandir("./", &namelist, 0, alphasort);
   int i;

   for ( i = 0; i < n; i++ )
   { 
      char *file_name = namelist[i]->d_name;

      strcpy(complete_filename, "./");
      strcat(complete_filename, "/");
      strcat(complete_filename, file_name);
 
      printf("%s\n", file_name);
   }
   
   return 0;
}

Basically, what I'm wondering is how I can use the stat structure to print such information. Can anyone help me out or at least point me in the right direction? (And the man pages are not much help for me).

If someone could just touch up my code so that it would print the date modified or something, so I could follow by example, that would be great.

#2 14-Mar-2006, 06:52

Quote:

Originally Posted by smoothdogg00

Currently, I have a program that lists the contents of a directory. What I need to do (as I've sort of started) is to use the stat structure to print such things as date modified, etc. like the "ls" program does. My code is as follows:

<snipped>

Basically, what I'm wondering is how I can use the stat structure to print such information. Can anyone help me out or at least point me in the right direction? (And the man pages are not much help for me).

If someone could just touch up my code so that it would print the date modified or something, so I could follow by example, that would be great.

Try man 2 stat and man 3 asctime. Hopefully this will get you going with stat-ing your file information...

CPP / C++ / C Code:

#include <sys/types.h>
#include <sys/stat.h>
#include <dirent.h>
#include <unistd.h>
#include <string.h>
#include <time.h>

int main()
{
    char complete_filename[2048] = {0};
    struct dirent **namelist;
    struct stat file_info;
    int n = scandir("./", &namelist, 0, alphasort);
    int i;
    struct tm last_modified;

    for( i = 0; i < n; i++ )
    {
        char *file_name = namelist[i]->d_name;

        strcpy(complete_filename, "./");
        strcat(complete_filename, "/");
        strcat(complete_filename, file_name);

        //printf("%s\n", file_name);
        if( strlen( file_name ) > 0 )
        {
            stat( &complete_filename[0], &file_info );
            localtime_r( &file_info.st_mtime, &last_modified );
            printf( "Filename: %s\nModified: %s\n\n", file_name, asctime( &last_modified ) );
        }
    }

    return 0;
}

// output:

Filename: .
Modified: Tue Mar 14 04:25:11 2006


Filename: ..
Modified: Tue Mar 14 04:21:49 2006


Filename: dirstat
Modified: Tue Mar 14 04:25:11 2006


Filename: dirstat.o
Modified: Tue Mar 14 04:25:11 2006

ls -la produces:

drwxrwxr-x  2 davis davis 4096 Mar 14 04:25 .
drwxr-xr-x  3 davis davis 4096 Mar 14 04:21 ..
-rwxrwxr-x  1 davis davis 8320 Mar 14 04:25 dirstat
-rw-rw-r--  1 davis davis 4284 Mar 14 04:25 dirstat.o

...I created a simple C app called "dirstat" and compiled it. This is the output of the "Debug" directory that my Linux editor (www.slickedit.com) creates whenever I make a "GCC Project" that it manages. I ran the executable "dirstat" from that directory on the files that it contained. You can see that the output of the program corresponds to what ls tells me about the files.

If I run the program from the directory above it:

Code:


$ ./Debug/dirstat

Filename: .
Modified: Tue Mar 14 04:21:49 2006


Filename: ..
Modified: Tue Mar 14 04:09:24 2006


Filename: Debug
Modified: Tue Mar 14 04:25:11 2006


Filename: dirstat.c
Modified: Tue Mar 14 04:25:10 2006


Filename: dirstat.mak
Modified: Tue Mar 14 04:10:07 2006


Filename: dirstat.vpj
Modified: Tue Mar 14 04:10:06 2006


Filename: dirstat.vpw
Modified: Tue Mar 14 04:09:26 2006


Filename: dirstat.vpwhistu
Modified: Tue Mar 14 04:10:07 2006


Filename: dirstat.vtg
Modified: Tue Mar 14 04:25:10 2006


ls outputs:

drwxr-xr-x   3 davis davis  4096 Mar 14 04:21 .
drwxr-xr-x  12 davis davis  4096 Mar 14 04:09 ..
drwxrwxr-x   2 davis davis  4096 Mar 14 04:25 Debug
-rw-rw-r--   1 davis davis  1596 Mar 14 04:25 dirstat.c
-rw-rw-r--   1 davis davis  1606 Mar 14 04:10 dirstat.mak
-rw-rw-r--   1 davis davis  4980 Mar 14 04:10 dirstat.vpj
-rw-rw-r--   1 davis davis   196 Mar 14 04:09 dirstat.vpw
-rw-rw-r--   1 davis davis   115 Mar 14 04:10 dirstat.vpwhistu
-rw-r--r--   1 davis davis 90112 Mar 14 04:25 dirstat.vtg

You can see that you'll want to modify your formatting, but this should get you a few more steps down the road to your "ls" program.

Note that I made your buffer a lot larger. I figured that eventually you were going to recurse directories. However, you should probably use strncat and strncpy to ensure that you never exceed the bounds of your char array.

:davis:

smoothdogg00 · #3 14-Mar-2006, 08:19

This is all very helpful, thanks a lot!

smoothdogg00 · #4 14-Mar-2006, 16:43

Ok, so I'm getting a pretty good understanding for this stuff now, but when I'm going to recurse the directories, how do I enter the next directory?

For example: Scandir is scanning the current directory and getting the files (and folders I'm assuming), but what call should be made in order to open the next directory down? Or maybe the question I need to ask, how can I recognize and open folders? Is it basically a "try scandir" and if it works, go with it, if not, try the next file?

mina_canada · #5 14-Mar-2006, 17:00

Thank you so much davis

#6 14-Mar-2006, 18:06

Quote:

Originally Posted by smoothdogg00

Or maybe the question I need to ask, how can I recognize and open folders?

Use the st_mode member of your stat struct and the S_ISDIR(m) macro where m = your st_mode member. It will return a value if the file mode is a directory. Then scandir it and other directories under it until you've recursed the entire world.

Check out section 8.6 in K&R (2nd Edition). They have an example of walking the directories.

:davis:

smoothdogg00 · #7 14-Mar-2006, 18:57

I was actually looking at that earlier, but I couldn't quite understand how to use it. Is there also some macro for determining if a file is "hidden" or not? Or should it just be determined by the "." in front?

<Edit>I got it under control, forget that question.<Edit>

smoothdogg00 · #8 14-Mar-2006, 20:32

I am now building an array within a while loop (of set size 500) that keeps track of all the directories within a directory. After those are added to the array, I am trying to copy the contents of that array to a new (smaller) array as follows:

Variables:

CPP / C++ / C Code:

char buf[255];
int i, dirs = 0;
int n = scandir(path, &namelist, 0, alphasort);
char * templist[n];

Code:

CPP / C++ / C Code:

for(code here)
{
    if(strncmp(file_name, ".", 1) && S_ISDIR(file_info.st_mode))
      {
          strcpy(templist[dirs], buf);
          dirs++;
      }
}

char * dirlist[dirs];

for(i = 0; i < dirs; i++)
    strcpy(dirlist[i], templist[i]);

I also already tried:

CPP / C++ / C Code:

templist[dirs] = buf;

But I obviously encountered pointer problems with that.

Note: All "if" statements, "for" loops and the "dir" counter work correctly.

#9 14-Mar-2006, 22:39

Quote:

Originally Posted by smoothdogg00

I was actually looking at that earlier, but I couldn't quite understand how to use it. Is there also some macro for determining if a file is "hidden" or not? Or should it just be determined by the "." in front?

<Edit>I got it under control, forget that question.<Edit>

You need to understand that the example in K&R is reentrant. The way to really do it is by hand coding the code into a separate program, building it and stepping through it with a debugger. All you really need to do is set a break-point at each function entry point so that you can track how the reentrancy works under any known directory "file" contents.

Try doing: "vi ." and, after it complains about "." being a directory, look at the contents of the file...or use "vi /usr/include" ...you'll get a lot of directory entries and a lot of "regular" file entries.

The more you understand about a "directory" mode file, the easier it will be to implement a solution that uses them. It helps to think about "how would I do it, if it wasn't already done." In other words, how you would implement a directory file so that when you did "dir" or "ls" that it would show the directories and regular files (and so forth) separately from each other? If you did "ls ." (which is the same as "ls"), you would use the CWD or current working directory for your input. We know that the CWD is implemented as a file named "."

If we view the contents of the file named "." we would see the subdirs and regular files under "." contained in it. When we mkdir, we create a "." dir entry named by the argument passed into mkdir. We cannot make a dir called "." as for any path that exists, it (".") will already be named.

The operating system is responsible for abstracting the IO subsystem such that it is represented as a file system to us with a C interface.

If you haven't read Tanenbaum's "Modern Operating Systems," you need to give it a quick look-through.

Let me know how it goes, if you want me to, I'll write a quick implementation to help you through it.

:davis:

smoothdogg00 · #10 14-Mar-2006, 23:58

Nevermind the last post.

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search
Rate This Thread
Rate This Thread:

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Listing directory information (C)	smoothdogg00	C Programming Language	1	10-Mar-2006 13:17
File listing of a directory	durrson	C Programming Language	2	17-Mar-2005 16:59
Denying directory listing and htaccess question	meet_raman	Apache Web Server Forum	11	01-Jul-2004 11:20
Apache2 config issues	monev	Apache Web Server Forum	2	28-Jun-2004 07:19
Can't view pages from another machine on the Intranet	aevans	Apache Web Server Forum	9	14-May-2004 03:26

Using stat.h and listing directory contents...

Re: Using stat.h and listing directory contents...

Re: Using stat.h and listing directory contents...

Re: Using stat.h and listing directory contents...

Re: Using stat.h and listing directory contents...

Re: Using stat.h and listing directory contents...

Re: Using stat.h and listing directory contents...

Re: Using stat.h and listing directory contents...

Re: Using stat.h and listing directory contents...

Re: Using stat.h and listing directory contents...