Storing list of file names as a string array?

[aggsyb]

Hi, I am using the following code I found to list all files with a .txt extension within a folder.

//GetFileNames Function
void getFileNames()
{
   WIN32_FIND_DATA search_data;

   memset(&search_data, 0, sizeof(WIN32_FIND_DATA));

   HANDLE handle = FindFirstFile("C:\\textfiles\\*.txt", &search_data);
  
   while(handle != INVALID_HANDLE_VALUE)
   {
      std::cout <<"Found file: " << search_data.cFileName << std::endl;
	
      if(FindNextFile(handle, &search_data) == FALSE)
         break;
	}
   
}

inside the text files folder I have text1 , text 2 , text 7 , text 9 etc all listed correctly in the console. My question is how can I store the file names in an array? I will change the function from a void to an int and I want it to grab all the filenames, store them in an array and pass them back to the main function. So the end result will have

string fileName[5000];

fileName[0] holds first file , fileName[1] next etc etc.

Cheers

[Dy7SLyTq]

http://www.cplusplus.com/reference/vector/vector
like an array only better. and to return it alls you have to do is:

vector<string> GetFileNames()
{
     vector<string> FileList;
     //your code
     return FileList;
}

[aggsyb]

I know how to create and use a string array but the question is how can I get each file name individually from the list of all the files into the array and pass it back.

I Have not used vectors yet but I guess no better time than the present! , when I return the file list vector do I have to store that return into another vector as the file list vector is outside my main functions scope?

So given the code I posted how would I store each file name correctly? I am unsure of where I can loop to store

[BlakeK]

I second DTSCode… Vectors are much better and would work perfectly here.

If I get what you're saying here…

I Have not used vectors yet but I guess no better time than the present! , when I return the file list vector do I have to store that return into another vector as the file list vector is outside my main functions scope?

…I think there is a better solution than copying that result into yet another vector.

You could change your code to something like…

// A file to include...
#include <vector>

/* Note the new function signature...
 * We are passing in a pointer to an existing vector
 */
void getFileNames(std::vector<std::string> *fileList)
{
	WIN32_FIND_DATA search_data;
	
	memset(&search_data, 0, sizeof(WIN32_FIND_DATA));
	
	HANDLE handle = FindFirstFile("C:\\textfiles\\*.txt", &search_data);
	
	while(handle != INVALID_HANDLE_VALUE)
	{
		std::cout <<"Found file: " << search_data.cFileName << std::endl;
		
		/* Here, you append another found file to the end of the vector.
		 * However, unlike arrays, you do NOT have to worry about resizing.
		 * The vector is resized for you!
		 */
		fileList->push_back(search_data.cFileName);
		
		if(FindNextFile(handle, &search_data) == FALSE)
			break;
	}
	
	/* Because you are passing vector as pointer to function, there is
	 * nothing to return, thus, we don't have to:
	 *   (1) write all the file names to a vector
	 *   (2) copy that vector to a new vector
	 * You'll just end up doing number 1.
	 */
}

A sample call to that function could go something like…

std::vector listOfFiles;
getFileNames(&listOfFiles); // <-- Using function here

std::cout << "A list of .txt files:\n";

for (std::vector<int>::iterator it = listOfFiles.begin() ; it != listOfFiles.end(); ++it)
{
	std::cout << *it << '\n' ;
}

The code I gave may not be 100% correct because I can't test it (I'm not using Windows), but you should get the idea. Yeah vectors may sound intimidating, but they're really, really useful and easier to deal with than arrays.

[aggsyb]

Thanks for the reply Im giving it a shot ! getting a few compiler errors through when trying to define listOfFiles for the call. I changed

std::vector listOfFiles; (red underscore error with listOfFiles)

to

std::vector <std::string> *listOfFiles;

that worked fine but

getFileNames(&listOfFiles); gives a red underscore under the &

Any suggestions? appreciate the help!

[Dy7SLyTq]

could you post your code?

[aggsyb]

#include <iostream>
#include <Windows.h>
#include <vector>

/* Note the new function signature...
 * We are passing in a pointer to an existing vector
 */

//Prototype
void getFileNames(std::vector<std::string> *fileList);

int main()
{
	std::vector listOfFiles;
	getFileNames(&listOfFiles); // <-- Using function here

	std::cout << "A list of .txt files:\n";

	for (std::vector<int>::iterator it = listOfFiles.begin() ; it != listOfFiles.end(); ++it)
	{
		std::cout << *it << '\n' ;
	}
}

void getFileNames(std::vector<std::string> *fileList)
{
	WIN32_FIND_DATA search_data;
	
	memset(&search_data, 0, sizeof(WIN32_FIND_DATA));
	
	HANDLE handle = FindFirstFile("C:\\textfiles\\*.txt", &search_data);
	
	while(handle != INVALID_HANDLE_VALUE)
	{
		std::cout <<"Found file: " << search_data.cFileName << std::endl;
		
		/* Here, you append another found file to the end of the vector.
		 * However, unlike arrays, you do NOT have to worry about resizing.
		 * The vector is resized for you!
		 */
		fileList->push_back(search_data.cFileName);
		
		if(FindNextFile(handle, &search_data) == FALSE)
			break;
	}
	
	/* Because you are passing vector as pointer to function, there is
	 * nothing to return, thus, we don't have to:
	 *   (1) write all the file names to a vector
	 *   (2) copy that vector to a new vector
	 * You'll just end up doing number 1.
	 */
}

Pmuch an exact copy and paste to test, line 14 is completley underscored and listOfFiles in line 15 is underscored.

[Dy7SLyTq]

@line 14 you need a type for vector to hold
@ line 41 i would do fileList->push_back(std::string(search_data.cFileName));

[aggsyb]

#include <iostream>
#include <Windows.h>
#include <vector>

/* Note the new function signature...
 * We are passing in a pointer to an existing vector
 */

//Prototype
void getFileNames(std::vector<std::string> *fileList);

int main()
{
std::vector <std::string> listOfFiles;
getFileNames(&listOfFiles); // <-- Using function here

std::cout << "A list of .txt files:\n";

for (std::vector<int>::iterator it = listOfFiles.begin() ; it != listOfFiles.end(); ++it)
{
	std::cout << *it << '\n' ;
}
}

void getFileNames(std::vector<std::string> *fileList)
{
	WIN32_FIND_DATA search_data;
	
	memset(&search_data, 0, sizeof(WIN32_FIND_DATA));
	
	HANDLE handle = FindFirstFile("C:\\textfiles\\*.txt", &search_data);
	
	while(handle != INVALID_HANDLE_VALUE)
	{
		std::cout <<"Found file: " << search_data.cFileName << std::endl;
		
		/* Here, you append another found file to the end of the vector.
		 * However, unlike arrays, you do NOT have to worry about resizing.
		 * The vector is resized for you!
		 */
		fileList->push_back(std::string(search_data.cFileName));
		
		if(FindNextFile(handle, &search_data) == FALSE)
			break;
	}
	
	/* Because you are passing vector as pointer to function, there is
	 * nothing to return, thus, we don't have to:
	 *   (1) write all the file names to a vector
	 *   (2) copy that vector to a new vector
	 * You'll just end up doing number 1.
	 */
}

Ok I made the changes, but line 19 is giving errors on:

listOfFiles.begin() (list of files is underscored) and

it != listOfFiles.end(); ++it) the != is underscored

[Dy7SLyTq]

vector::iterator not vector<int>::iterator

[BlakeK]

I knew I would forget the type for the vector somewhere!

Either change lines 14 & 15 to...

std::vector<std::string> listOfFiles; // No pointer
getFileNames(&listOfFiles);

...or…

std::vector<std::string> *listOfFiles; // Pointer
getFileNames(listOfFiles);  // Passing pointer instead of value 

[aggsyb]

Tried DTS suggestion which did not work alo tried both of your Blakek and I a still getting the same errors in line 19 but this time both underscores are under listOfFiles. If I try DTS method I get underscored under most of line 19, hmm

[Dy7SLyTq]

a) i would honestly use a range based for loop
b) could you post the code and errors?

[aggsyb]

#include <iostream>
#include <Windows.h>
#include <vector>

/* Note the new function signature...
 * We are passing in a pointer to an existing vector
 */

//Prototype
void getFileNames(std::vector<std::string> *fileList);

int main()
{
std::vector<std::string> listOfFiles; // No pointer
getFileNames(&listOfFiles);

std::cout << "A list of .txt files:\n";

for (std::vector::iterator it = listOfFiles.begin() ; it != listOfFiles.end(); ++it)
{
	std::cout << *it << '\n' ;
}
}

void getFileNames(std::vector<std::string> *fileList)
{
	WIN32_FIND_DATA search_data;
	
	memset(&search_data, 0, sizeof(WIN32_FIND_DATA));
	
	HANDLE handle = FindFirstFile("C:\\textfiles\\*.txt", &search_data);
	
	while(handle != INVALID_HANDLE_VALUE)
	{
		std::cout <<"Found file: " << search_data.cFileName << std::endl;
		
		/* Here, you append another found file to the end of the vector.
		 * However, unlike arrays, you do NOT have to worry about resizing.
		 * The vector is resized for you!
		 */
		fileList->push_back(std::string(search_data.cFileName));
		
		if(FindNextFile(handle, &search_data) == FALSE)
			break;
	}
	
	/* Because you are passing vector as pointer to function, there is
	 * nothing to return, thus, we don't have to:
	 *   (1) write all the file names to a vector
	 *   (2) copy that vector to a new vector
	 * You'll just end up doing number 1.
	 */
}

The error is:

1>------ Build started: Project: Testing vector, Configuration: Debug Win32 ------
1> Source.cpp
1>c:\users\ben\documents\visual studio 2012\projects\programming exercises\hh project\testing vector\testing vector\source.cpp(19): error C2955: 'std::vector' : use of class template requires template argument list
1> c:\program files (x86)\microsoft visual studio 11.0\vc\include\vector(655) : see declaration of 'std::vector'
1> c:\program files (x86)\microsoft visual studio 11.0\vc\include\vector(655) : see declaration of 'std::vector'
1> c:\program files (x86)\microsoft visual studio 11.0\vc\include\vector(655) : see declaration of 'std::vector'
1>c:\users\ben\documents\visual studio 2012\projects\programming exercises\hh project\testing vector\testing vector\source.cpp(21): warning C4552: '<<' : operator has no effect; expected operator with side-effect
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

Its not declaring the vector when I make the changes you suggested , I also tried changing it from std::vector<int>::iterator to std::vector<std::string>::iterator which didnt work either , currently using whats in the source though. Sorry it probably seems basic and dumb for me to be getting this wrong but as I said I have no experience with vectors yet.

[Dy7SLyTq]

replace your for loop with mine

for(auto &Itr : ListOfFiles)
cout<< Itr << endl;

[aggsyb]

for(auto &Itr : listOfFiles)
cout << Itr << endl;

the first << is giving an error, mouseover shows "No operator << match these operands , operand types are std::ostream << std::string"

[BlakeK]

Okay, so I finally fired up a Windows machine so I could run the code being typed.

The following worked for me. However, I noticed <string> is not being included, but the program still compiles fine for me. However, you will probably need to include the file, as I am using MinGW-supplied headers with g++. You seem to be using the Microsoft supplied headers with VC++ compiler. For another example of having to include <string> in VC++ but not MinGW, see http://stackoverflow.com/a/9084404/1130172.

#include <iostream>
#include <Windows.h>
#include <vector>

/* Note the new function signature...
 * We are passing in a pointer to an existing vector
 */

//Prototype
void getFileNames(std::vector<std::string> *fileList);

int main()
{
	std::vector<std::string> listOfFiles; // No pointer
	getFileNames(&listOfFiles);

	std::cout << "A list of .txt files:\n";

	for (std::vector<std::string>::iterator it = listOfFiles.begin() ; it != listOfFiles.end(); ++it)
	{
		std::cout << *it << '\n' ;
	}
}

void getFileNames(std::vector<std::string> *fileList)
{
	WIN32_FIND_DATA search_data;

	memset(&search_data, 0, sizeof(WIN32_FIND_DATA));

	HANDLE handle = FindFirstFile("C:\\textfiles\\*.txt", &search_data);

	while(handle != INVALID_HANDLE_VALUE)
	{
		std::cout << "Found file: " << search_data.cFileName << std::endl;

		/* Here, you append another found file to the end of the vector.
		 * However, unlike arrays, you do NOT have to worry about resizing.
		 * The vector is resized for you!
		 */
		fileList->push_back(std::string(search_data.cFileName));

		if(FindNextFile(handle, &search_data) == FALSE)
			break;
	}

	/* Because you are passing vector as pointer to function, there is
	 * nothing to return, thus, we don't have to:
	 *   (1) write all the file names to a vector
	 *   (2) copy that vector to a new vector
	 * You'll just end up doing number 1.
	 */
}

[aggsyb]

Oh god! how embarrassing I forgot to include string haha , works great :D.

So thats working great, my vector has all the information stored, how would I access elements of that vector?

for example if this was a string array and it found 4 text files then the 4th would in array[3] , the first would be in array[0] and i could simple

std::cout << array[0] ;

but with a vector how do I access elements for a simple cout?

[Dy7SLyTq]

same way. there are others but thats the most common. there is also at(I) where I is an int and it returns the corresponding element

[aggsyb]

Working perfectly , thank you both for your help ill no doubt be posting a new question in a few hours when I get stuck , cheers!