Thread: SEEK_CUR issue

Hi,

I know I am not done with this, but I get an error that I don't know how to fix.

I am trying to lower the inventory count of this data file.

named productdata.txt
id, price, and count

Code:

   0 0.00 99   1 1.00 10   2 2.00 20   3 3.00 30   4 4.00 40   5 5.00 50   6 6.00 60   7 7.00 70   8 8.00 80   9 9.00 90

I wrote this:
to get into and do the work:

Code:

 #include <stdio.h>
 #include <stdlib.h>
 #include "product.h"
 #define IDSize 4
 #define PriceSize 5
 #define CountSize 3
 #define RecordSize (IDSize+PriceSize+CountSize)

 int main ( int argc, char** argv )
 {
     int count;
     int currentID;
     int inputID;
     FILE *myfile;
     int set;
     int i;
     int oldCount;

     //fgets( FileName, sizeof( FileName ), stdin );

     //if( FileName[strlen( FileName ) - 1] == '\n' )
     //{
     //    FileName[strlen( FileName ) - 1] = '\0';
     //}
     myfile = fopen(FileName, "r");
     if (myfile == NULL)
     {
         printf("Cannot open %s\n", FileName);
         return(1);
     }

     printf( "Enter the ID of the product you wish to change: ");
     scanf( " %d", &inputID);

     for( i = 0; i < NumProducts; i++ )
     {
        if( inputID == Product[i].id )
         {
            break;
         }
     }

     while(1)
     {
         set = fscanf( FileName, "%d", currentID);

         if (set == 0)
         {
             break;
         }
         if( currentID == inputID )
         {
             fseek( FileName, PriceSize, SEEK_CUR );
             fscanf( FileName, " %d", &count);
             count--;
             oldCount = count;
             fseek( FileName, -CountSize, SEEK_CUR );
             fprintf( FileName, "%3d", count);
             break;
         }
         fseek( FileName, PriceSize + CountSize , SEEK_CUR );
     }
     printf( "Count of product ID %d changed from %d to %d\n", inputID, oldCount , count);
     return (0);
}

I was given this header to include as is:

Code:

#define FileName "productdata.txt"
#define NumProducts 10
#define RecordSize (4+5+3)

struct Product
{
    int        id;        // four-digit product ID code
    float    price;    // xx.xx product price (5 characters)
    int        count;    // three-digit count of units in stock
};
typedef  struct Product  Product;

I am getting an error at:

Code:

if( inputID == Product[i].id )

won't compile and gives error:

syntax error before "Product"

I am confused.

As I said I know the program is not done yet but it will compile if I comment out:

Code:

for( i = 0; i < NumProducts; i++ )
     {
        if( inputID == Product[i].id )
         {
            break;
         }
     }

Which obviously includes the problem code.

Am I supposed to reference the header file?

ok thanks
I declared

Code:

Product product;

with the rest of the declarations and now I get:

the variable 'product' is being used without being initialized.
here

Code:

for( i = 0; i < NumProducts; i++ )
     {
        if( inputID == product.id[i] )
         {
            break;
         }
     }

That means you haven't actually put any data into your struct variable before using it. It contains junk data which you're comparing against.

Why not just:

Code:

typedef struct
{
    int        id;        // four-digit product ID code
    float    price;    // xx.xx product price (5 characters)
    int        count;    // three-digit count of units in stock
} PRODUCT;
PRODUCT product;

instead of typing these stuff all over when you wanna to create a "PRODUCT-based" variable.

@ eXeCuTeR - The only answer I have for that is...I have to, it's part of the deal.

@ Elysia - I know the variable is full of garbage, I am reading and searching and didn't see anything on how to get the data into the struct and then into the FILE* so I can manipulate it.

If I weren't already voluntarily bald....

Well, I'm not sure how your program works, but to write data, you can use fwrite, fprintf and for reading fread. You can read into a string and then convert it to appropriate data type and store in the struct. I don't know if there's an equalient function for reading as opposed to fprintf, though.

hmm, I don't think I need this after all:

Code:

for( i = 0; i < NumProducts; i++ )
     {
        if( inputID == Product[i].id )
         {
            break;
         }
     }