Thread: Methods and file pointers

I am pretty confident that I wrote my requestFileName correctly, but my program crashes every time I run it, so I am assuming I wrote out fileScan incorrectly.

Code:

void requestFileName(FILE **fp) 
{   
	char inputFilename[30];				// Character Array to hold the users specified input file name
	printf("Enter the name of the file to be scanned: "); 	
	scanf("%s", inputFilename);			// Scans the input file specified by the user 	
	printf("\n");						// adds a space in between file names and file statistics 	
	*fp = fopen(inputFilename, "r");	// open the file as read-only 
}
/*	Stores values from the input file into the variables cityName, population, squareMileafe, pollution,
	crime, expense, and highways. */
void fileScan(FILE **fp, char cityName, int population, int squareMileage, int pollution, int crime, int expense, int highways)
{
	fscanf(fp, "%s %d %d %d %d %d %d", cityName, population, squareMileage, pollution, crime, expense, highways);
}

In my main method I call fileScan like:

Code:

while(fileScan(&fp, cityName, population, squareMileage, pollution, crime, expense, highways) != EOF)	// get next char from input file until we reach EOF
	{
//...
         }

What am i doing incorrectly?

Originally Posted by Aia

Code:

void requestFileName(FILE *fp)  /* remove one  * */
{   
	char inputFilename[30];				// Character Array to hold the users specified input file name
	printf("Enter the name of the file to be scanned: "); 	
	scanf("%s", inputFilename);
	printf("\n");						// adds a space in between file names and file statistics 	
	fp = fopen(inputFilename, "r");	 /* remove the * in *fp */
}

My professor told me i needed to use FILE **fp. :\ but maybe I misunderstood.

I also get this as a warning:

"Warning 3 warning C4013: 'fileScan' undefined; assuming extern returning int"

Is it not working correctly because fileScan is not returning the correct declaration?

Originally Posted by drater

I also get this as a warning:

"Warning 3 warning C4013: 'fileScan' undefined; assuming extern returning int"

Is it not working correctly because fileScan is not returning the correct declaration?

It means just what it says: you haven't defined a function called fileScan.

Now you may have done so later in the file, but by then the damage is done. You did remember to put a function prototype of fileScan at the top of the file, didn't you?

I took out the void, and Now i am getting 2 warnings which I don't understand:
Warning 3 warning C4028: formal parameter 1 different from declaration
Warning 4 warning C4028: formal parameter 2 different from declaration

Code:

/*	Requests the user to input a valid file name to be scanned */
void requestFileName(FILE **fp) 
{   
	char inputFilename[30];				// Character Array to hold the users specified input file name
	printf("Enter the name of the file to be scanned: "); 	
	scanf("%s", inputFilename);			// Scans the input file specified by the user 	
	printf("\n");						// adds a space in between file names and file statistics 	
	*fp = fopen(inputFilename, "r");	// open the file as read-only 
}

/*	Stores values from the input file into the variables cityName, population, squareMileafe, pollution,
	crime, expense, and highways. */
fileScan(FILE *fp, char cityName, int population, int squareMileage, int pollution, int crime, int expense, int highways)
{ /*     BOTH ERRORS APPEAR HERE     */

	fscanf(fp, "%s %d %d %d %d %d %d", cityName, population, squareMileage, pollution, crime, expense, highways);
}

Originally Posted by drater

I took out the void, and Now i am getting 2 warnings which I don't understand:
Warning 3 warning C4028: formal parameter 1 different from declaration
Warning 4 warning C4028: formal parameter 2 different from declaration

Code:

/*	Requests the user to input a valid file name to be scanned */
void requestFileName(FILE **fp) 
{   
	char inputFilename[30];				// Character Array to hold the users specified input file name
	printf("Enter the name of the file to be scanned: "); 	
	scanf("%s", inputFilename);			// Scans the input file specified by the user 	
	printf("\n");						// adds a space in between file names and file statistics 	
	*fp = fopen(inputFilename, "r");	// open the file as read-only 
}

/*	Stores values from the input file into the variables cityName, population, squareMileafe, pollution,
	crime, expense, and highways. */
fileScan(FILE *fp, char cityName, int population, int squareMileage, int pollution, int crime, int expense, int highways)
{ /*     BOTH ERRORS APPEAR HERE     */

	fscanf(fp, "%s %d %d %d %d %d %d", cityName, population, squareMileage, pollution, crime, expense, highways);
}

Try again, and this time pay attention: you do not have a function prototype for fileScan. Therefore your code will not work. Put a function prototype for fileScan at the top of the file, or put it in an included header file.

Code:

/* prototype call */

fileScan(FILE **fp, char *cityName, int population, int squareMileage,
			  int pollution, int crime, int expense, int highways);

Code:

/*  Main Call */
while(fileScan(fp, cityName, population, squareMileage, pollution, crime, expense, highways) != EOF)	// get next char from input file until we reach EOF
	{
            //...
         }

Code:

/* method */
fileScan(FILE *fp, char cityName, int population, int squareMileage, int pollution, int crime, int expense, int highways)
{ /*ERRORS: Warning 3 warning C4028: formal parameter 1 different from declaration
Warning 4 warning C4028: formal parameter 2 different from declaration */
	fscanf(fp, "%s %d %d %d %d %d %d", cityName, population, squareMileage, pollution, crime, expense, highways);
}

I put int in both my prototype call and function call and added a return statement, I no longer receive:
Warning: formal parameter 1 different from declaration,
But i do receive Warning: formal parameter 2 different from declaration.

Also I would like to thank everyone who has responded and put up with my stupidity.