dirent, stat, compar & alphasort

Old_Spen · #1 04-May-2005, 04:12

I was trying yo modify the directory listing example in the man pages to sort the files by time but I just don't seem to get how to do it.

Problem is that I ain't no C pro.

Need help urgently..... My code is as follows:

CPP / C++ / C Code:


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

main(){

struct stat fnm1, fnm2;
struct dirent a, b;
struct dirent **namelist;

int compar(struct dirent **pa, struct dirent **pb)
        {
        struct dirent a, b;
        a = **pa; b = **pb;
        return -strcmp(a.d_name, b.d_name);
}

/*
int alphasort (struct dirent **pa, sturct dirent **pb)
{
return strcmp((*pa)->d_name, (*pb)->d_name);
}
*/

int n;

   n = scandir(".", &namelist, 0, *compar);

   if (n < 0)
       perror("scandir");
   else {
   if (stat("(n->d_name)", &fnm1)==0 && stat("(n->d_name)", &fnm2) == 0)
        {
        double tdiff = difftime(fnm1.st_time, fnm2.st_time);
        while(n--) {
           printf("%s\n", namelist[n]->d_name);
           free(namelist[n]);
        }
      }

       free(namelist);
   }

}

As you can see, I even tried using the alphasort option but to no avail. Was using Turbo C but now trying to migrate to Gnu C

Any help would be nice.

Thanks

Old_Spen

WaltP · #2 05-May-2005, 00:09

To the tune of Wagner's Ride of the Valkries
That's Elmer Fudd's "Kill the Wabbit" to you youngsters...
Read the Sticky -- Read the Sticky -- ...

You need to give us more information... We can't see anything if you don't tell us where to look.

Old_Spen · #3 06-May-2005, 14:13

Quote:

Originally Posted by WaltP

To the tune of Wagner's Ride of the Valkries
That's Elmer Fudd's "Kill the Wabbit" to you youngsters...
Read the Sticky -- Read the Sticky -- ...

You need to give us more information... We can't see anything if you don't tell us where to look.

Well actually my program does not result in anything as I keep getting a warning on the illegal typecasting of a pointer to an int.

The original program for listing the directory contents in the linux manpages is:

CPP / C++ / C Code:


       /* print files in current directory in reverse order */
       #include <dirent.h>
       main(){
	   struct dirent **namelist;
	   int n;

	   n = scandir(".", &namelist, 0, alphasort);
	   if (n < 0)
	       perror("scandir");
	   else {
	       while(n--) {
		   printf("%s\n", namelist[n]->d_name);
		   free(namelist[n]);
	       }
	       free(namelist);
	   }
       }

What I am trying to do is adapt the above manpage example to display the file names according to when they were last modified or accessed using the functions for time, stat alphasort and the same thing using compar.

I think this is supposed to be done with scandir if I am not mistaken.

Hope this clarifies my needs.

Cheers,

Old_Spen

WaltP · #4 06-May-2005, 16:11

Quote:

Originally Posted by Old_Spen

Well actually my program does not result in anything as I keep getting a warning on the illegal typecasting of a pointer to an int.

I hate to harp on the obvious, but read guideline 1.4b and 2.4. We can't help if we don't know where the error is....

Quote:

Originally Posted by Old_Spen

The original program for listing the directory contents in the linux manpages is:

CPP / C++ / C Code:


       /* print files in current directory in reverse order */
       #include <dirent.h>
       main(){
	   struct dirent **namelist;
	   int n;

	   n = scandir(".", &namelist, 0, alphasort);
	   if (n < 0)
	       perror("scandir");
	   else {
	       while(n--) {
		   printf("%s\n", namelist[n]->d_name);
		   free(namelist[n]);
	       }
	       free(namelist);
	   }
       }

1) Does that program work? If not, start by getting this one to work.
2) Is this the same as your program? If not, we obviously can't tell you what you did wrong in your program.

Quote:

Originally Posted by Old_Spen

What I am trying to do is adapt the above manpage example to display the file names according to when they were last modified or accessed using the functions for time, stat alphasort and the same thing using compar.

I think this is supposed to be done with scandir if I am not mistaken.

Since you didn't post any code using time(), stat(), alphasort(), nor compar() we can't tell what might be wrong.

Quote:

Originally Posted by Old_Spen

Hope this clarifies my needs.

Not a lot... Hope this clears up what we need to know to help you, though.

Old_Spen · #5 11-May-2005, 00:58

Quote:

Originally Posted by WaltP

I hate to harp on the obvious, but read guideline 1.4b and 2.4. We can't help if we don't know where the error is....

1) Does that program work? If not, start by getting this one to work.
2) Is this the same as your program? If not, we obviously can't tell you what you did wrong in your program.

Since you didn't post any code using time(), stat(), alphasort(), nor compar() we can't tell what might be wrong.

Not a lot... Hope this clears up what we need to know to help you, though.

The man page code is:

CPP / C++ / C Code:

#include <stdio.h>
#include <dirent.h>

main(){
 struct dirent **namelist;
   int n;
   n = scandir(".", &namelist, 0, alphasort);
   if (n < 0)
       perror("scandir");
   else {
       while(n--) {
           printf("%s\n", namelist[n]->d_name);
           free(namelist[n]);
       }
       free(namelist);
   }
}

It returns this:

t.c
t
scandir.c
scandir
gemgeh.c
gemgeh
fork1.c
fork.c
fork
dsin1.c
dsin.c
dsin
..
.

****************************

My code to return directory contents based on time last modified is:

CPP / C++ / C Code:

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

main(){

struct stat fnm1, fnm2;
struct dirent a, b;
struct dirent **namelist;

int compar(struct dirent **pa, struct dirent **pb)
        {
        struct dirent a, b;
        a = **pa; b = **pb;
        return -strcmp(a.d_name, b.d_name);
}

/*
int alphasort (struct dirent **pa, sturct dirent **pb)
{
return strcmp((*pa)->d_name, (*pb)->d_name);
}
*/

int n;

   n = scandir(".", &namelist, 0, *compar);

   if (n < 0)
       perror("scandir");
   else {
   if (stat("(n->d_name)", &fnm1)==0 && stat("(n->d_name)", &fnm2) == 0)
        {
        double tdiff = difftime(fnm1.st_time, fnm2.st_time);
        while(n--) {
           printf("%s\n", namelist[n]->d_name);
           free(namelist[n]);
        }
      }

       free(namelist);
   }


}

The error I get from my code is:

Quote:

cc dsin.c -o dsin
dsin.c: In function `main':
dsin.c:30: warning: passing arg 4 of `scandir' from incompatible pointer type
dsin.c:37: structure has no member named `st_time'
dsin.c:37: structure has no member named `st_time'
make: *** [dsin] Error 1

Dave Sinkula · #6 11-May-2005, 08:46

As the message states, st_time isn't there because it doesn't need to be.
http://www.opengroup.org/onlinepubs/...ys/stat.h.html

Code:

DESCRIPTION

    The <sys/stat.h> header shall define the structure of the data returned by the functions fstat(), lstat(), and stat().

    The stat structure shall contain at least the following members:

dev_t     st_dev     Device ID of device containing file. 
ino_t     st_ino     File serial number. 
mode_t    st_mode    Mode of file (see below). 
nlink_t   st_nlink   Number of hard links to the file. 
uid_t     st_uid     User ID of file. 
gid_t     st_gid     Group ID of file. 
[XSI][Option Start]
dev_t     st_rdev    Device ID (if file is character or block special). 
[Option End]
off_t     st_size    For regular files, the file size in bytes. 
                     For symbolic links, the length in bytes of the 
                     pathname contained in the symbolic link. 
[SHM][Option Start]
                     For a shared memory object, the length in bytes. 
[Option End]
[TYM][Option Start]
                     For a typed memory object, the length in bytes. 
[Option End]
                     For other file types, the use of this field is 
                     unspecified. 
time_t    st_atime   Time of last access. 
time_t    st_mtime   Time of last data modification. 
time_t    st_ctime   Time of last status change. 
[XSI][Option Start]
blksize_t st_blksize A file system-specific preferred I/O block size for 
                     this object. In some file system types, this may 
                     vary from file to file. 
blkcnt_t  st_blocks  Number of blocks allocated for this object. 
[Option End]

What compiler are you using? Its documentation ought to tell you what stuff is there.

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dirent, stat, compar & alphasort

Clarification