Thread: Structure Problem

I'm using a structure to store first and last name from a sequential access file. I can scan them in and believe I am loading them into the structure correctly. The problem I am having is swapping the output using printf. If you look in my switch under case 1, you will see that I am trying to print the informatino in my structure in reverse order. I have tried a number of different ways and this is my latest attempt. Can you see what I am doing wrong? I have looked over it for too long.

Code:

#include <stdio.h>

	FILE * FilePtr;

int main()	{
	
	/*  This creates a client structure.  It is 
		used to store client information.  When we
		read from the file we will store our values in 
		the array structure */

	struct Client
	{
		char f_Name[15];
		char l_Name[15];
	} Record[5];	//Creates a structure array on client_record
	

	int i,number;

	/*  Lets open the client.dat file and see if we have opened
		it correctly... */

	FilePtr = fopen("client.dat", "r");
	if(FilePtr == NULL)
	{
		printf("Unable to access the disk file specified\n");
		exit(1);
	}
		

	/* If it was done correctly, we will attempt to load our structure array
		with information.  */

	else
	{
		printf("client.dat has been opened successfully!!!\n\n");
		printf("Reading File, printing output...\n\n");
		
		for( i = 0; i < 5; i++)
		{	
			while(fscanf(FilePtr, "%s %s", Record[i].f_Name, Record[i].l_Name) != EOF)
			printf("%s, %s \n", Record[i].l_Name, Record[i].f_Name);
			fclose(FilePtr);
		}

	}

	printf("\n\nWould you like to switch the name order from: \n");
	printf("Last Name, First to  First Name, Last? \n");
	printf("Press 1 for Yes, and 2 for No. \n");

	scanf("%d", &number);
	
	switch(number)
	{
		case 1:

			printf("Swapping...\n");
				
			
				printf("%s, %s \n", Record[4].f_Name, Record[4].l_Name);
				
				printf("%s, %s \n", Record[3].f_Name, Record[3].l_Name);
				
				printf("%s, %s \n", Record[2].f_Name, Record[2].l_Name);
				
				printf("%s, %s \n", Record[1].f_Name, Record[1].l_Name);
				
				printf("%s, %s \n", Record[0].f_Name, Record[0].l_Name);
			
			break;

		case 2:

			printf("Nevermind...\n");
			break;

		default:
			printf("Please enter a valid character!\n");
			break;
	}

	return 0;
}

Look at this loop (well, these two loops actually):

Code:

  for (i = 0; i < 5; i++)
  {
    while (fscanf(FilePtr, "%s %s", Record[ i ].f_Name, Record[ i ].l_Name) == 2)
      printf("%s, %s \n", Record[ i ].l_Name, Record[ i ].f_Name);
    fclose(FilePtr);
  }

You're problem is in there. Follow the flow of the two loops (there's in a hint in there ), and you'll find your problem.

I don't understand. Are you saying that my EOF argument is somehow messing up the rest of the operation? If I compile, and read in my data. The first part prints out fine. It seems to be storing it into my structure array fine. But when I get to the first select structure, case 1. It throws out a bunch of garbage, and the last record.

I should be able to access my array, as I have done. Unless I am not throwing the data into the array correctly. Can you be more specific.

>It seems to be storing it into my structure array fine.

No, it's not. Let's look at your version (I added the braces for clarity).

Code:

for( i = 0; i < 5; i++)
{	
	while(fscanf(FilePtr, "%s %s", Record[i].f_Name, Record[i].l_Name) != EOF)
	{
		printf("%s, %s \n", Record[i].l_Name, Record[i].f_Name);
	}
	fclose(FilePtr);
}

First time through the for loop: read the entire file into Record[0] in the while loop, printing each record as it is read, then close the file.
Second time through the for loop: attempt to read from the closed file pointer, leave junk in Record[1].
Third time through the for loop: attempt to read from the closed file pointer, leave junk in Record[2].
etc.

Maybe try a single-loop version like this.

Code:

for ( i = 0; i < 5; i++ )
{
   if ( fscanf(FilePtr, "%s %s", Record[i].f_Name, Record[i].l_Name) != 2 )
   {
      break;
   }
   printf("%d, %s, %s \n", i, Record[i].l_Name, Record[i].f_Name);
}
fclose(FilePtr);

Ahh I understand now. Thanks for your help guys. I'm going to have to work on my loops. I just couldn't see how it was looping, or how the fscanf worked. I have more experience working with VB so I was looking at it the wrong way. Thanks again.

Place the fclose(FilePtr); after for loop.