How should I approach this problem? r.e. How to use opendir()/scandir()

[Taylrl]

Hi,

I am currently writing a program but am beginning to see that I could have problems in the future due to the number of files that I may want to open with too many names to specify individually.

I have a series of .txt files. An unspecified number of them. I would like to open each of them in turn and read the data into my program. I am wondering whether I should copy the code each time I want to open a new file, changing the file specific parts or whether there is a more efficient way of going about it?

At the moment the program is only running on a set of test files but in the future I would be looking to expand it and could potentially have an huge number of files that I would be looking to open.

Also, is there a way of automatically detecting the filename and then using that as the name for say a vector or a variable in my program. I think I am going to really need the program to do this for me.

Thanks for your help! You people here are amazing! :-)

[Moschops]

You can feed the program a directory upon starting it, and have it read the contents of that directory, make a list of the contents, identify the files of interest by name, and then operate on each of those.

If you can nail down your requirements a bit more clearly, we can point you at helpful functions.

[Taylrl]

Great idea! That sounds ideal!! I'll have a little look into it :-)

Thanks!

[Taylrl]

Ok I think I need to use opendir(). I have found this piece of code but it is currently kicking out all kinds of errors. I was just wondering if someone might be so kind as to talk me through it somewhat. Here is what I have;

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

void scandir(char *dirname)
{
   DIR *dir;
   struct dirent *ent;

   printf("First pass on '%s':\n",dirname);
   if ((dir = opendir(dirname)) == NULL)
   {
     perror("Unable to open directory");
     exit(1);
   }
   while ((ent = readdir(dir)) != NULL)
     printf("%s\n",ent->d_name);

   printf("Second pass on '%s':\n",dirname);
   rewinddir(dir);
   while ((ent = readdir(dir)) != NULL)
     printf("%s\n",ent->d_name);
   if (closedir(dir) != 0)
     perror("Unable to close directory");
}

void main(int argc,char *argv[])
{
   if (argc != 2)
   {
     printf("usage: opendir dirname\n");
     exit(1);
   }
   scandir(argv[1]);
   exit(0);
}

I am currently replacing all the places where it says dirname with /directory1/directory2/ etc.

[Taylrl]

Ok I have got the code above to compile now, but what I would like it to be able to do is use it to open first, the first file in a directory. Then I have something I want to do to the data. I then want to move on to the next file and repeat the process.

Am I right in thinking that this code simply open a directory and not much more? I would like to be able to take the name of the first file in the directory and then open that file. Any Ideas how I might be able to achieve this?

Cheers! :-)

[coder777]

currently it's just printing the names on line 17. You could pass an array or better vector where you actually store the names.

I think the code from line 19 until 22 isn't necessary.

[Taylrl]

Wait this code is only printing on line 31 at the moment. I'll just check it.