Question on file access and sorting

[mhunt007]

Hi guys
I have been studying C on my own and want to access the contents of a file for the purpose of sorting them. I'm using 'bubble sort' because it seems a simple way to do content sorting. Anyway, my code compiles and runs but fails to print on screen the file content. Here is my code:

/* read, sort and display customer's id and balances */

   #include <stdio.h>
   #include <stdlib.h>
   #define MAX_CUSTOMERS 100
   
   struct custRec
   {
   	int ID;
   	float Bal;
   };
   
  /* prototypes of functions */
  int readInput(struct custRec *);
  void sortData(struct custRec *, int);
  void printRecords(struct custRec*, int);

  int main()
  {
  	int noOfRecords;
  	struct custRec custs[MAX_CUSTOMERS];
  	/* read the input */
  	noOfRecords = readInput(custs);
  	/* print the initial values */
  	printf("Before sorting\n");	
  	printRecords(custs,noOfRecords);
  	/* sort the array */
  	sortData(custs,noOfRecords);
  	/* print the sorted values */
  	printf("Ater sorting\n");
  	printRecords(custs,noOfRecords);
  	system("pause");
  	return 0;
   }
      
  /* read the input file and put data into the
     array that records points at  */

  int readInput(struct custRec *records)
  {
  	FILE *input = fopen("cust.dat","r");
  	int noOfRecords = 0;
  	char tempLane[240];
  	int tempCustId;
  	float tempCustBal;
  	if ( input == 0)	/* can't open cust.dat */
  	{
  		fprintf(stderr,"Can not open cust.dat\n");
  		fprintf(stderr,"please check\n\n");
  		exit(-1);
  	} 	
  	while (fgets(tempLane,240,input))
  	{
  		/* if the first character is a "#" ignore */
  		if (tempLane[0] == '#')
  		{
  			continue;
  		}
  		/* make sure that the line has 2 numbers */
  		if (sscanf(tempLane,"%d, %f",
  				&tempCustId, &tempCustBal) == 2)
  		{
  			records[noOfRecords].ID = tempCustId;
  			records[noOfRecords].Bal = tempCustBal;
  			noOfRecords++;
  		}
  	}
  	
  
  	fclose(input);
  	return noOfRecords;
  }   
   
  

/* sort the records */
void sortData(struct custRec *custs, int noOfRecs)
  {
  	int inner, outer, didSwap;
  	struct custRec temp;
  	/* sort the array */
  	for (outer = 1; outer < noOfRecs; outer++)
  	{
  		didSwap = 0;
  		for (inner = noOfRecs-1; inner >= outer ; inner--)
  		{
  			if (custs[inner-1].ID > custs[inner].ID )
  			{
  				temp = custs[inner-1];
  				custs[inner-1] = custs[inner];
  				custs[inner] = temp;
  				didSwap = 1;
  			}
  		} /* inner loop */
  		if (didSwap == 0)
  		{
  			break;
  		}
  	} /* outer loop */
  	return ;
  }
  
  void printRecords(struct custRec* custs, int noOfRecs)
 {
  	int i;
  	/* print values */
  	printf("Cust ID    Balance\n");
  	for (i = 0; i < noOfRecs ; i++)
  	{
  		printf("%5d %12.2f\n",
  			custs[i].ID, custs[i].Bal);
  	}
 	return;
 }

My input file, 'cust.dat', merely contains two columns of values with a header:


Cust ID Bal

313 0.00
453 45.43
502 71.23
101 301.56
892 9.08
475 192.41
792 389.00
912 229.67
343 18.31
633 59.54
999 1.00
0 0.00


Thanks for any help.

[tabstop]

Does it print before the sort? If not, check how many items are being read from the file (e.g. by printing noOfRecords).

EDIT:
And speaking of, look at your format:

"%d, %f"

Now look at your data.

[Adak]

I don't see where you pulled off the header line from the file. You have a char '#' set up to help you, but never use it in the input file.

You need to do that, first. Then print up the file values, to confirm that you are getting what you should be getting. (bugs can be quite subtle).

Then do your sorting, and redisplay the data, in sorted order.

Meter by meter, life is sweeter. Take it a step at a time.

[mhunt007]

Hi tabstop
No it only prints out

Before sorting
Cust ID Balance
After sorting
Cust ID Balance
Press any key to continue...

I see about the "%d, %f" and my file contents.

Thanks.

[mhunt007]

Hi Adak
I deleted the headers and so I only have the two columns of numbers. Still no printing of either the original numbers or the sorted version.

[Adak]

After the fgets(), if you print tempLane, what do you get, nothing?


Next step is seeing if the data gets into your other two temp variables. Print them out and see (or watch them in your debugger).

Step by step.

[mhunt007]

I inserted

printf(tempLane,"%d, %f", &tempCustId, &tempCustBal);

in the function

int readInput(struct custRec *records)
  {
  	FILE *input = fopen("cust.dat","r");
  	int noOfRecords = 0;
  	char tempLane[240];
  	int tempCustId;
  	float tempCustBal;
  	if ( input == 0)	/* can't open cust.dat */
  	{
  		fprintf(stderr,"Can not open cust.dat\n");
  		fprintf(stderr,"please check\n\n");
  		exit(-1);
  	} 	
  	while (fgets(tempLane,240,input))
  	{
  		/* if the first character is a "#" ignore */
  		if (tempLane[0] == '#')
  		{
  			continue;
  		}
  		/* make sure that the line has 2 numbers */
  		if (sscanf(tempLane,"%d, %f",
  				&tempCustId, &tempCustBal) == 2)
  		{
  			records[noOfRecords].ID = tempCustId;
  			records[noOfRecords].Bal = tempCustBal;
  			noOfRecords++;
  		}
  	}
  	
    printf(tempLane,"%d, %f",
  				&tempCustId, &tempCustBal);
  	fclose(input);
  	return noOfRecords;
  }

but still get nothing.

[mhunt007]

After the fgets(), if you print tempLane, what do you get, nothing?


Next step is seeing if the data gets into your other two temp variables. Print them out and see (or watch them in your debugger).

Step by step.

Hi Adak. How does one go about doing this? Thanks.

[Adak]

You may have a blank line at the start of the file?

Add a t to your file open mode to make it specify "rt" mode. (that used to goof me up often).

I'm running your program right now.

The problem is the silly little comma in your sscanf("%d, %f", etc);

[mhunt007]

You may have a blank line at the start of the file?

Add a t to your file open mode to make it specify "rt" mode. (that used to goof me up often).

I'm running your program right now.

Thanks. I put a 't' in for the 'rt' and checked the input file which does not have any blanks. I also played around with the input file but I still cannot get it to be printed onscreen. I tried another program which only opens the file and it does print the file contents to the screen.

/* seq2.c - an example reading a file */

#include <stdio.h>
#include <stdlib.h>

   int main()
   {
    char letter;
   	char fileLine[100];
   	int i;
   	FILE *fptr;
   	fptr = fopen("cust.dat", "r");
   	if (fptr == 0)
  	{
  		printf("An error occurred while opening the file.\n");
  		exit(1);
  	}
  	while (!feof(fptr))
  	{
  		fgets(fileLine,100,fptr);
  		if (!feof(fptr))
  		{
  			puts(fileLine);
  		}
  	}
  	
  	fclose(fptr);
  	system("pause");
  	return 0;
  }

[Adak]

Remove that comma from the sscanf() format area, and it works fine.

[vart]

instead of

while (!feof(fptr))
  	{
  		fgets(fileLine,100,fptr);
  		if (!feof(fptr))
  		{
  			puts(fileLine);
  		}
  	}

use

while (fgets(fileLine,100,fptr))
{
	puts(fileLine);
}

this is easier to read

[mhunt007]

Remove that comma from the sscanf() format area, and it works fine.

Thanks a lot Adak. I followed your suggestion and removed the comma between the "%d,%f"
and the program works fine. Strange that this would be enough to not allow the program to output to the console.

if (sscanf(tempLane, "%d %f",&tempCustId, &tempCustBal) == 2)

Anyway, I really appreciate your help. I'm learning C just to learn something new. Thanks.