opening multiple files c++

[prolink007]

I have never done this before and I am having trouble figuring out how to do this... here is the problem...

I need to be able to open a file, read in some values, then write those values to a different file. And i need to do this for about 100 files. These files are in several different sub directories of one parent directory.

What could i do to be able to have the program read in each file that is a child of the parent directory and a child of the sub directories of the parent directory?

The files are on a unix system.
The files have random names.
The files are all the same file type.
The files are all below a parent directory, but in sub directories of the parent.

Please assist me asap, THANKS in advance!!

[Duthomhas]

To get file names in a directory
http://linux.die.net/man/3/opendir
http://linux.die.net/man/3/readdir
http://linux.die.net/man/3/closedir

To get information about each file
http://linux.die.net/man/2/stat
For file type information, use the S_ISX() macros listed on the stat() man page.

Good luck!

[prolink007]

That actually helped a little bit, but here is a code snippet of what i have so far... as of right now, it is just going to the next level of directories and not going all the way through each directory, i need it to go through each subdirectory.

Also, i am not familiar with how to get it to list the files that are in that directory, i have been reading some about readdir(), but i am not familliar with it and having a hard time grasping how to use it.

Can someone please help me with this? Thanks in advance.

void GetFileListing(vector<string> &files, string dir, string filter)
{
    DIR *d;
    if ((d = opendir(dir.c_str())) == NULL) return;
    if (dir.at(dir.length() - 1) != '/') dir += "/";//maybe without the "-1"

    struct dirent *dent;
    struct stat st;

    while ((dent = readdir(d)) != NULL)
    {
    	string path = dir;

    	if (string(dent->d_name) != "." && string(dent->d_name) != "..")
    	{
    		path += string(dent->d_name);
    		const char *p = path.c_str();
    		lstat(p, &st);

    		if (S_ISDIR(st.st_mode))
    		{
    			GetFileListing(files, (path + string("/")).c_str(), filter);
    		}
    	}
    }
    closedir(d);
}

[PanGalactic]

You might have better luck with the Boost Filesystem library: http://www.boost.org/doc/libs/1_38_0/libs/filesystem/doc/index.htm

[Duthomhas]

Perhaps you are looking for something like the following:

#include <iostream>
#include <string>
#include <vector>

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

typedef std::vector <std::string> DirListing_t;

void GetDirListing( DirListing_t& result, const std::string& dirpath )
  {
  DIR* dir = opendir( dirpath.c_str() );
  if (dir)
    {
    struct dirent* entry;
    while ((entry = readdir( dir )))
      {
      struct stat entryinfo;
      std::string entryname = entry->d_name;
      std::string entrypath = dirpath + "/" + entryname;
      if (!stat( entrypath.c_str(), &entryinfo ))
        {
        if (S_ISDIR( entryinfo.st_mode ))
          {
          if      (entryname == "..");
          else if (entryname == "." ) result.push_back( dirpath + "/" );
          else                        GetDirListing( result, entrypath );
          }
        else
          {
          result.push_back( entrypath );
          }
        }
      }
    closedir( dir );
    }
  }

using namespace std;

int main( int argc, char* argv[] )
  {
  if (argc != 2)
    {
    cout << "usage:\n  " << argv[ 0 ] << " DIRPATH\n"
         << "Display the directory tree for the directory DIRPATH.\n";
    return 0;
    }

  DirListing_t dirtree;

  GetDirListing( dirtree, argv[ 1 ] );

  for (unsigned n = 0; n < dirtree.size(); n++)
    cout << dirtree[ n ] << endl;

  return 0;
  }

It is a little different than yours -- it also lists the directory names it finds due to the condition on line 28 (using "/" in liu of "/."). The "/.." entry is still omitted. So, for example, my first test produced:

D:\prog\cc\foo> g++ -Wall -pedantic a.cpp

D:\prog\cc\foo> a .
./
./a.cpp
./a.exe

D:\prog\cc\foo> _
(Of course, I also tested it for other directories with recursion, etc...)

It does not list directories or files for which the user does not have access permissions (which causes stat() to fail).

It also doesn't mess with the source path. Notice how I used a relative path? Here are three other runs and their results:

D:\prog\cc\foo> a D:\prog\cc\foo
D:\prog\cc\foo/
D:\prog\cc\foo/a.cpp
D:\prog\cc\foo/a.exe

D:\prog\cc\foo> a /prog/cc/foo
/prog/cc/foo/
/prog/cc/foo/a.cpp
/prog/cc/foo/a.exe

D:\prog\cc\foo> a ../a
../a/
../a/a.cpp
../a/a.exe

You may want to add in some normalization on the dirpath argument to convert "\" to "/", collapse "." and ".." entries, and even get the absolute pathname (which is often unnecessary).

One last feature possibility is to return results relative to the initial dirpath... this doesn't take too much extra work.

Hope this helps.

[prolink007]

Thanks for all the help, i actually got what i was aiming for completed. Now i have another question, i am going to open up a new topic for this one...