Write-to-file problems

This is a discussion on Write-to-file problems within the C Programming forums, part of the General Programming Boards category; Hello. I am trying to save some data to a txt file by using fprintf but for some reason the ...

  1. #1
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    Exclamation Write-to-file problems

    Hello.

    I am trying to save some data to a txt file by using fprintf but for some reason the files I get are empty. The program creates the files fine, but for some reason it does not write anything to them.
    It has worked before, but I had to make some changes to my program when this problem occurred. I have tried to find the problem for many hours now, but with no result.
    I even tried using fopen_s instead of the normal fopen, but with no improvements.

    Any help or suggestions will be greatly appreciated.

    Here's the code of one of my header files (I have isolated the file from calling other functions for debug (you never know) by using comments //:

    Code:
    #include <stdio.h>
    
    handleBoard(int param, int dimY, int dimX, int X, int Y, int totalMines)
    {
    	int i, j, a, b, count = 0;
    
    	char** minesArray;
    	FILE *MinesFile, *DisplayFile;
    	
    	MinesFile = fopen("MinesFile.txt","w+");
    	DisplayFile = fopen("DisplayFile.txt","w+");
    	
    	// ALLOCATING A TWO-DIMENTIONAL DYNAMIC ARRAY FOR BOARD
    	minesArray = (char**)malloc(dimX*sizeof(char*));
    	for (i = 0; i < dimX; i++)
    	{  
    		minesArray[i] = (char*)malloc(dimY * sizeof(char));
    	}
    
    	if (param == 0)
    	{
    		
    		// SETTING ALL TILES TO STATUS 0 (CLOSED TILE ,NO MINE), EXCEPT FOR TILE AT X,Y WHICH GETS STATUS 2 (OPEN TILE, NO MINE)
    		for (i=0;i<dimX;i++)
    		{
    			for (j=0;j<dimY;j++)
    			{
    				if ((i == X) && (j == Y))
    				{
    					minesArray[i][j] = '2';
    				}
    				else
    				{
    					minesArray[i][j] = '0';
    				}
    			}
    		}
    		
    		// PLANTING MINES AT RANDOM TILES WHILE ASSURING THAT NO MINE IS PLANTED AT X,Y
    		for (i=0;i<totalMines;i++)
    		{
    			a = rand() % dimX;
    			b = rand() % dimY;
    			if (minesArray[a][b] == '2')
    			{
    				i--;
    			}
    			else if (minesArray[a][b] == '1')
    			{
    				i--;
    			}
    			else if (minesArray[a][b] == '0')
    			{
    				minesArray[a][b] = '1';
    			}
    			else
    			{
    				printf("ERROR AT RAND()");
    			}
    		}
    		
    		// SAVING DISPLAY- AND MINES DATA TO FILE
    		for (i=0;i<dimX;i++)
    		{
    			for (j=0;j<dimY;j++)
    			{
    				fprintf(MinesFile,"1");
    
    				if ((minesArray[i][j] == '0') || (minesArray[i][j] == '1'))
    				{
    					fprintf(DisplayFile,"c");
    				}
    				else if (minesArray[i][j] == '2')
    				{
    					fprintf(DisplayFile,".");
    				}
    			}
    		}		
    
    		fclose(MinesFile);
    		fclose(DisplayFile);
    	}
    
    
    
    
    
    	else if (param == 1)
    	{
    		// LOADING DATA FROM FILE TO MEMORY
    		for (i = 0; i < dimX; i++)
    		{
    			for (j = 0; j < dimY; j++)
    			{
    				minesArray[i][j] = fgetc(MinesFile);
    			}
    		}
    
    		// CHECKING IF SELECTED TILE HAS NEIGHBOURING MINES
    		if (minesArray[X][Y] = '0')
    		{
    			//count = check4Neighbours(dimY, dimX, X, Y);
    		}
    
    		// IF IT HAS 1 OR MORE NEIGHBOURING MINES...
    		if (count > 0)
    		{
    			minesArray[X][Y] = (char)count;
    
    			// SAVING DATA TO FILE
    			for (i=0;i<dimX;i++)
    			{
    				for (j=0;j<dimY;j++)
    				{
    					fprintf(MinesFile,"%c",minesArray[i][j]);
    				}
    			}		
    			fclose(MinesFile);
    			fclose(DisplayFile);
    		}
    	}
    }
    Last edited by dcdude; 04-25-2011 at 12:07 PM.

  2. #2
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    First of all, I would split saving the mines file and the board file into two separate functions. It may look clever the way you did it but in the end there are just too many things to go wrong.

    Next... open file, write data, close file ... do you see anything between those three steps?
    And there should be nothing between them in your code either. Never, ever keep a file open even a millisecond longer than it needs to be.

    Finally you are not checking the returned value from either of your file open functions... so you proceed to write to the files without knowing if they actually opened or not. You should always check returned values in any I/O operation and do not proceed with step B unless step A has succeeded.

  3. #3
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    Thank you CommonTater for your quick reply.

    Opening the file right before writing, and closing it immediatly after solved my problem... thank you very much!

  4. #4
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    Quote Originally Posted by dcdude View Post
    Thank you CommonTater for your quick reply.

    Opening the file right before writing, and closing it immediatly after solved my problem... thank you very much!
    Gald to help.

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