appending structure bin file

Can anyone please help me with an example of appending the end of a structure in a binary file. For instance, I have an array of 1000 structures, and for instance, so far the user has only wrote to the structure 300. I know hoe to open the file with fopen and fread, but what sort of code would I use to allow the user to write to the next available structure?

Code:

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struct database {
  char prod[60];
  float cal;
  float carb;
  float prot;
  float fat; 
};

struct database mainm[1000];

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instead of opening it with fopen("output.bin", "wb") use fopen("output.bin","ab")

Quote:

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instead of opening it with fopen("output.bin", "wb") use fopen("output.bin","ab")

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Mode a opens the file for appending - that is, all new data is written to the end of the file. Any existing data is left alone (not truncuated, like with mode w).

Ive tried but it will only write write to the structure which I specify, and if I dont specify a number I just get an error when compiling. This is what Im trying to do:

Code:

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FILE *fp = fopen("output.dat", "ab");
 
      printf("\nEnter the product:");
      fgets(mainm.prod, 60, stdin);
      if ((p = strchr(mainm.prod, '\n')) != NULL) //clears \n
      *p = '\0';
      system("cls");
      printf("\nNow Please Enter The Nutritional Information:");
      printf("\nEnter cal:");
      scanf("%f", &mainm.cal);
      fflushstdin();
      printf("\nEnter carb:");
      scanf("%f", &mainm.carb);
      fflushstdin();
      printf("\nEnter protein:");
      scanf("%f", &mainm.prot);
      fflushstdin();
      printf("\nEnter fat:");
      scanf("%f", &mainm.fat);
      system("cls");
      fflushstdin();
      }

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I assume p is declared as

Code:

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char *p;

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So you want to input the user's data into a structure, a different one each time? Like this?

Code:

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int x;
struct {int i;} s[10];
for(x = 0; x < 10; x ++) {
    /* read in structure s[x] */
}

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OK thanks dwk. What would be the best way to break this loop if the user wanted to quit?

With break. Like so:

Code:

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for(/*...*/) {
    /* ... */
    printf("\nAnother? (Y/N) ");
    if(getchar() == 'n') break;
}

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Cn you please tell me what Im doing wrong as its not working properly

Code:

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#include<stdlib.h>
#include<stdio.h>
#include<conio.h>
#include<windows.h>
#include<string.h>
#include<time.h>

#define EXIT o;


//structure to hold all info, final program will contain structures of main meal, snacks
//and also deserts, using this structure

struct database {
  char prod[60];
  float cal;
  float carb;
  float prot;
  float fat; 
};

//function prototypes

int full_screen(void);//puts the dos console to full screen when called
void main_menu(void);
void about_opt(void);
void help_opt(void);
void fflushstdin( void );//clears scanf when called
void clrscr(void); //clears the screen when called


FILE *fp;

struct database *point1;




int main()
{
   
   
 
 full_screen(); //Puts the dos console into full screen when program is executed


  struct database mainm[10];
 
  main_menu();


 
  char buf[BUFSIZ];
  char *p;                     
  int i;
  int x;
  FILE *fp;


  for ( i = 0; i < 10; i++)
 

  {
      printf("\nAnother? (Y/N) ");
    if(getch() == 'n') break;
   

      printf("\nEnter the product:");
      fgets(mainm[i].prod, 60, stdin);
      if ((p = strchr(mainm[i].prod, '\n')) != NULL)
      *p = '\0';
      system("cls");
      printf("\nNow Please Enter The Nutritional Information:");
      printf("\nEnter cal:");
      scanf("%f", &mainm[i].cal);
      fflushstdin();
      printf("\nEnter carb:");
      scanf("%f", &mainm[i].carb);
      fflushstdin();
      printf("\nEnter protein:");
      scanf("%f", &mainm[i].prot);
      fflushstdin();
      printf("\nEnter fat:");
      scanf("%f", &mainm[i].fat);
      system("cls");
      fflushstdin();
      }
     
     
fp = fopen("output.dat", "ab");
     
fwrite(mainm, 1, sizeof(struct database) * 10, fp);
fclose(fp);

fp = fopen("output.dat", "rb");
fread (mainm, 1, sizeof(struct database) * 10, fp);
fclose(fp);

int a;

for ( a = 0; a <10; a ++)
{
    clrscr();
   
printf("\n * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *");
printf("\n\nThe nutritional values for ");
HANDLE h = GetStdHandle ( STD_OUTPUT_HANDLE );
WORD wOldColorAttrs;
CONSOLE_SCREEN_BUFFER_INFO csbiInfo;
GetConsoleScreenBufferInfo(h, &csbiInfo);
wOldColorAttrs = csbiInfo.wAttributes;

SetConsoleTextAttribute ( h, FOREGROUND_RED | FOREGROUND_INTENSITY );
printf("%s", mainm[a].prod);
SetConsoleTextAttribute ( h, wOldColorAttrs);                                       
printf(" item # %d are:",a);
printf("\n\nCALORIES - ");
SetConsoleTextAttribute ( h, FOREGROUND_RED | FOREGROUND_INTENSITY );
printf("%f", mainm[a].cal);
SetConsoleTextAttribute ( h, wOldColorAttrs);
printf("\n\nCARBOHYDRATES - ");
SetConsoleTextAttribute ( h, FOREGROUND_RED | FOREGROUND_INTENSITY );
printf("%f", mainm[a].carb);
SetConsoleTextAttribute ( h, wOldColorAttrs);
printf("\n\nPROTEIN - ");
SetConsoleTextAttribute ( h, FOREGROUND_RED | FOREGROUND_INTENSITY );
printf("%f", mainm[a].prot);
SetConsoleTextAttribute ( h, wOldColorAttrs);
printf("\n\nFAT - ");
SetConsoleTextAttribute ( h, FOREGROUND_RED | FOREGROUND_INTENSITY );
printf("%f\n\n", mainm[a].prot);
SetConsoleTextAttribute ( h, wOldColorAttrs);
printf("\n* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *");
printf("\n\nPress return for next product...");

getch();

}

}

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What's it not doing? Or doing?

This code

Code:

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    printf("\nAnother? (Y/N) ");
    if(getch() == 'n') break;

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Should probably go at the end of the for loop, so that the user has to enter at least one structure before being prompted.

You call main_menu() in main(). main_menu() is not listed here, although you probably have it somewhere. Perhaps main_menu() never returns?