C / C++ / MFC

23-Feb-09 22:42

I want to open all files with a certain name and/or a certain type, but for that I need to know the contents of a directory first.
How do I see them?

Thanks.

«_Superman_»23-Feb-09 22:51

«_Superman_»

23-Feb-09 22:51

FindFirstFile and FindNextFile should do it.

«_Superman_»
I love work. It gives me something to do between weekends.

Hamid_RT23-Feb-09 23:18

Hamid_RT

23-Feb-09 23:18

See Code for finding out the total number of files & folders existing in a folder through VC++[^] it has some helpful info for you.

Of one Essence is the human race
thus has Creation put the base
One Limb impacted is sufficient
For all Others to feel the Mace
(Saadi )

Megidolaon24-Feb-09 2:21

24-Feb-09 2:21

Thanks.
I got something (I think) with FindFirstFile and FindNextFile.

Though, it doesn't quite work, this whole code is in a try catch block, but still throws a System.AccessViolationException (which is .NET specific and I can't use it or acces it) and does nothing:

try
{
   fstream file;
   vector<lpwin32_find_dataw> files;
   LPCTSTR namepointer;
   HANDLE handle;
   string line = "";
   int i = 0;
   int size;
   char directory [] = "C:\\Folder";
   char *stringpointer = directory ;
	
   files.assign(1, LPWIN32_FIND_DATAW());
   handle = FindFirstFile(namepointer, files[i]);
		
   while (handle != INVALID_HANDLE_VALUE)
   {
      FindNextFile(handle, files[i]);
      files.assign(1, LPWIN32_FIND_DATAW());
      i++;
   }	
   size = files.size();

   cout << files.size() << endl;
   for (int k = 0; k < size; k++)
   {
      cout << "Reading File:" << files[k]->cFileName << endl;
   }
   getchar();
   return 0;
}
catch (exception ex)
{
   cout << "An error has occurred." << endl;
   cout << ex.what() << endl;
}</lpwin32_find_dataw>

I want to read the filenames to check if they're txt files with the right kind of name and then read from them to process the text of each.

Thanks.

David Crow24-Feb-09 3:17

24-Feb-09 3:17

Megidolaon wrote:
...but still throws a System.AccessViolationException...

Where/when?

Why do you have a vector of WIN32_FIND_DATA structures? One is sufficient.

Megidolaon wrote:
handle = FindFirstFile(namepointer, files[i]);

What is the value of namepointer?

"Old age is like a bank account. You withdraw later in life what you have deposited along the way." - Unknown

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Megidolaon24-Feb-09 20:30

24-Feb-09 20:30

It throws the exception right at the start and does nothing else.

DavidCrow wrote:
Why do you have a vector of WIN32_FIND_DATA structures? One is sufficient.

FindFirstFile and FindNextFile seemed to return only as single file, so I assumed LPWIN32_FIND_DATAW represented a single file.
How does that work anyway?
The struct only has a few attributes that seem like file attributes, which wouldn't make much sense in a collection (like filename or creation date).

Originally I had

namepointer = stringpointer;

but that won't do.

I get an error that char* cannot be converted to LPCTSTR.
I must have deleted the line and didn't notice.
Though, it was done like that in the article Hamid posted (then again, I got 10 errors from that code).

David Crow25-Feb-09 3:16

25-Feb-09 3:16

Megidolaon wrote:
FindFirstFile and FindNextFile seemed to return only as single file, so I assumed LPWIN32_FIND_DATAW represented a single file.

It does, hence the need for a loop.

Look through this snippet to see where you went awry:

vector<string> files;
WIN32_FIND_DATA findData;
BOOL bFound = TRUE;
 
HANDLE handle = FindFirstFile("C:\\*.*", &findData);		   
if (handle != INVALID_HANDLE_VALUE)
{
    while (bFound)
    {
        files.push_back(findData.cFileName);
        bFound = FindNextFile(handle, &findData);      
    }	   
}
 
for (int k = 0; k < files.size(); k++)   
    cout << "Reading File:" << files[k].c_str() << endl;

Megidolaon25-Feb-09 21:31

25-Feb-09 21:31

Thanks, though this code stil throws 2 errors.

First one that I can't convert from const char[7] to LPCWSTR (in FindFirstFile).
Second one is that I can't convert from WCHR[260] to std::string & (files.push_back(findData.cFileName);).

David Crow26-Feb-09 2:43

26-Feb-09 2:43

Megidolaon wrote:
Thanks, though this code stil throws 2 errors.

That's because you are using Unicode. Change string to wstring and prepend the string literal with an L.

Megidolaon27-Feb-09 0:20

27-Feb-09 0:20

I see now it compiles.
But the program doesn't quite work.
It doesn't display anything and when setting a breakpoint it takes over a minute until it reaches it (first call of FindFirstFile)

After that line I get an error, saying that there is no cource code available for the current position.
I don't get any error or output if I don't use a breakpoint.

David Crow27-Feb-09 3:15

Re: How do I read the contents of a directory? [modified]

27-Feb-09 3:15

Megidolaon wrote:
It doesn't display anything...

Does the files vector contain anything?

What does your code look like?

Megidolaon1-Mar-09 20:36

1-Mar-09 20:36

vector<wstring> files;
	WIN32_FIND_DATA findData;
	BOOL bFound = TRUE;
	 
	HANDLE handle = FindFirstFile(L"C:\Dokumente und Einstellungen\Student\Eigene Dateien", &findData);		   
	if (handle != INVALID_HANDLE_VALUE)
	{
		while (bFound)
		{
			files.push_back(findData.cFileName);
			bFound = FindNextFile(handle, &findData);      
		}	   
	}
	 
	for (int k = 0; k < files.size(); k++)   
	{
		cout << "Reading File:" << files[k].c_str() << endl;   
	}

getchar();</wstring>

I copied your code and used wstring, then added an L to the filepath, as you said.
I used getchar(), to keep the console open.
I made a break point at the line of files.push_back(findData.cFileName);, but the program never reaches that line.
It simply does nothing, probably because when I put a breakpoint at the FindFirstFile line and then go the next line with F11, I get an error telling me that for the current position no source code is avaiable.

modified on Monday, March 2, 2009 5:23 AM

David Crow2-Mar-09 2:27

2-Mar-09 2:27

Megidolaon wrote:
HANDLE handle = FindFirstFile(L"C:\Dokumente und Einstellungen\Student\Eigene Dateien", &findData);

You need to use double backslashes.

What is the value of handle?

Megidolaon2-Mar-09 3:07

2-Mar-09 3:07

I have double backslashes, codeproject didn't display the code properly.
I tried it with this conde and with using \\*.* at the ne dof the filepath, but it's the same.
I get that error in both cases.

David Crow2-Mar-09 3:14

2-Mar-09 3:14

Megidolaon wrote:
I have double backslashes, codeproject didn't display the code properly.

CodeProject does not care if, or how many, backslashes are used.

Megidolaon wrote:
I get that error in both cases.

What error?

Have you checked the return value of FindFirstFile()? If it is INVALID_HANDLE_VALUE, have you called GetLastError()?

Megidolaon2-Mar-09 20:21

2-Mar-09 20:21

I cannot check the return value of FindFirstFile because if I set a breakpoint, I get the error that the code is unavalable for the current position at the line of the FindFirstFile function.

David Crow3-Mar-09 2:51

3-Mar-09 2:51

Megidolaon wrote:
I cannot check the return value of FindFirstFile...

What's keeping you from doing this:

vector<string> files;	
WIN32_FIND_DATA findData;	
BOOL bFound = TRUE;	 	
 
HANDLE handle = FindFirstFile(L"C:\\Dokumente und Einstellungen\\Student\\Eigene Dateien\\*.*", &findData);		   	
if (handle != INVALID_HANDLE_VALUE)	
{		
    while (bFound)		
    {			
        files.push_back(findData.cFileName);			
        bFound = FindNextFile(handle, &findData);      		
    }	   	
 
    for (int k = 0; k < files.size(); k++)   	
        cout << "Reading File:" << files[k].c_str() << endl;   	
}
else
    cout << GetLastError() << endl;;
 
getchar();

Megidolaon5-Mar-09 21:06

5-Mar-09 21:06

I use this, but I get this error when trying to read the names from the vector.

error C2664: 'void std::basic_ofstream<_Elem,_Traits>::open(const wchar_t *,std::ios_base::openmode,int)': Covertion of Parameter 1 from 'std::basic_string<_Elem,_Traits,_Ax>' to 'const wchar_t *' not possible

I use wofstream to open the files, but I get that error when trying to read the names from the vector, yet I don't get an error when using a const filename (a random string literal).

Also I get this error multiple times from getline():

error C2784: "std::basic_istream<_Elem,_Traits> &std::getline(std::basic_istream<_Elem,_Traits> &,std::basic_string<_Elem,_Traits,_Alloc> &)": template-Argument for "std::basic_istream<_Elem,_Traits> &" could not be deducted from "std::wofstream"

It's the same error regardless if line is a string or a wstring.

David Crow6-Mar-09 2:17

6-Mar-09 2:17

This is a different problem altogether. What does your code to open and read from a file look like?

Megidolaon8-Mar-09 21:44

8-Mar-09 21:44

This is my code:

vector<wstring> files;
	WIN32_FIND_DATA findData;
	BOOL bFound = TRUE;
	HANDLE handle;
	string name ="";
	wofstream myfile;
	wstring line;

	handle = FindFirstFile(L"C:\\Dokumente und Einstellungen\\Student\\Eigene Dateien\\*.mp", &findData);		   
	
	if (handle != INVALID_HANDLE_VALUE)
	{
		while (bFound)
		{
			files.push_back(findData.cFileName);
			bFound = FindNextFile(handle, &findData);      
		}	   
	}
	else
	{
		cout << GetLastError() << endl;
	}

	for (int k = 0; k < files.size(); k++)   
	{
		
         myfile.open(files.at(k));
		
	    while (myfile.eof() == false)
	    {
		getline(myfile, line);
		wcout << line << endl;
	    }
	    myfile.close();
	}</wstring>

It's pretty much the same as you posted, except that I use wofstream instead of ofstream and wsring for line instead of string.
And I use wcout instead of cout.

.mp files are just txt files with a different extension.

David Crow9-Mar-09 3:39

9-Mar-09 3:39

Megidolaon wrote:
wofstream myfile;

This should be an "input" file since you are reading from it.

Megidolaon wrote:
myfile.open(files.at(k));

at() returns a string, not a const char *. Hint: use the c_str() method.

Megidolaon10-Mar-09 1:51

10-Mar-09 1:51

Thanks, now I don't get an error anymore.
However, it still doesn't work properly.

The program does nothing.
myfile.eof == false() never is wrong, apparently the file end is never reached.
I set a breakpoint and files contains 3 strings at runtime (this is correct).
Each of the files has 43 lines for a total of 129 lines;
I use

counter++;
cout << counter << ": ";

Where counter is an int, starting a 0, to output the line numbers.
It passes 129 almost instantly and the while loop is infinte and line always is "".
How come?
Why doesn't open() actually open the files or at least gives me some kind of error, why it won't work?
And more importantly, how does it work?

Thanks.

David Crow10-Mar-09 3:15

10-Mar-09 3:15

Have you tried something like:

while (myfile.good())
{
    myfile.getline(line, sizeof(line));
    wcout << line << endl;
}

Megidolaon11-Mar-09 0:35