How to sequentially read all the files in a directory

Hi,
I've done a lot of searching and haven't found any good ideas about this. It must be simple. I'm not an experienced C++ programmer and I haven't quite grasped the concepts of data abstraction and classes, so I'm probably still thinking with the old "top-down" paradigm.

Admittedly, by getting some code from the "snippets" page and other internet sources, I'm trying to work with functions that I don't thoroughly understand.


Here's a description of what I want to do.

Loop (in a directory)
read file names in the directory into file_name[i] array
end of loop

Loop through input file_name[] array
open each input file
read about 250 lines of data into arrays
zero out math variables
do some math
perform some tests
if pass all tests?
output file_name[i] to a an output file
close file

end of loop

The following came from the snippets page and is used to read
all the filenames in the directory. It works.
I added the lines to load the file_name[] array which also works.
I could probably skip that step and do all my operations within the
while(FindNextFile....)loop, but keeping the steps separate is easier
for me to keep organized.

Code:

---

// read all the filenames in a directory
//************************************************************
WIN32_FIND_DATA FindFileData;
HANDLE hFind = INVALID_HANDLE_VALUE;
char DirSpec[MAX_PATH]; // directory specification

cout<<"Path: ";
cin.get(DirSpec, MAX_PATH);
cout<<"\n";
strncat(DirSpec, "\\*", 3);
hFind = FindFirstFile(DirSpec, &FindFileData);

        if(hFind == INVALID_HANDLE_VALUE)
        {
        cout<<"Error: invalid path\n";
        }


//
// Read the files in the directory and assign
// the filenames to the file_name[] array

int i;
string file_name[7000]; 
//yes, I need to learn how to handle a variable length string array!
//number of files could vary but will be around 6500

    i = 0;
    int file_count = 0;

        while(FindNextFile(hFind, &FindFileData) != 0)
        {
    file_name[i] = FindFileData.cFileName;
        //cout<<FindFileData.cFileName<<"\n";
        i++;
        file_count++;
        }


FindClose(hFind);

//output one example
cout<<"file 12 is "<<file_name [12]<<"\n\n";  //this works

//***********************************************************

---

After I fill the file_names[] array, I want to loop through the files, read
lines of data and perform operations. This is the part I haven't figured out.


I'm trying to use the following as the basis to loop through the files
My test files are consistent with the averaging routine here
but this is just a test:

Code:

---

//************************************************************
#include <iostream>
#include <fstream>  // needed for files
using namespace std;


int main(void)
  {
  fstream InFile;
  float Num, Total;
  int Count;

// I want to put the following into a loop and somehow replace "readfile.txt"
// with file_name[j]

  InFile.open("readfile.txt", ios::in);
  if (InFile.fail())
      {
      cout << "Could not open readfile.txt" << endl;
      exit(1);
      }

  Count = 0;
  Total = 0.0;

  InFile >> Num;

  while (! InFile.fail())
      {
      Total = Total + Num;
      Count++;
      InFile >> Num;
      }

  if (Count > 0)
      cout << "Average is " << Total / Count << endl;
  else
      cout << "No data given" << endl;

  InFile.close();
  return 0;
  }
//***********************************************************

---

I guess my real question is: Is the Infile.open("readfile.txt"....) line
extendable so that it could be used to loop through the file_name[] array?
Sort of like the following (this doesn't work, it's just to get the idea
of what I'm trying to do):

Code:

---

For ( j = 1; j <= file_count; j++)
        {
        InFile.open(file_name[j], ios::in);
        //read lines of data
        //perform operations
        InFile.close();
        }

---

Alternately, does anybody know a good C++ book where you can look up what you are trying to do and find some good examples of how to do it.

Thanks,
Rich

.open requires a char * (a/k/a a C-style string), not a std::string, for the first parameter. So you'll have to convert:

Code:

---

InFile.open(file_name[j].c_str(), ios::in);

---

Code:

---

#include <iostream>
#include <fstream>
using namespace std;

int main()
{
    const char* pString1 = "test.txt";
    const char* pString2 = "test2.txt";

    const char* file_name[] = {pString1, pString2};
    int file_count = sizeof(file_name) / sizeof(char*);

    for (int i = 0 ; i < file_count; i++)
    {
        float fValue = 0.0f;
        ifstream inFile(file_name[i]);
        while (!inFile.eof())
        {
            inFile >> fValue;
            cout << fValue << endl;
        }
        cout << endl << endl;
    }

    return 0;
}

---

Be sure to read this, as well, before making any more replies: http://cboard.cprogramming.com/cplus...ead-first.html

Code:

---

#include <iostream>

using namespace std;

int main()
{
    cout << "Thank you Elysia" << endl;
    cout << "This is much nicer!" << endl;
    return 0;
}

---