appending structure bin file

This is a discussion on appending structure bin file within the C Programming forums, part of the General Programming Boards category; Can anyone please help me with an example of appending the end of a structure in a binary file. For ...

  1. #1
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    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:
    struct database {
      char prod[60];
      float cal;
      float carb;
      float prot;
      float fat;  
    };
    
    struct database mainm[1000];

  2. #2
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    instead of opening it with fopen("output.bin", "wb") use fopen("output.bin","ab")

  3. #3
    Frequently Quite Prolix dwks's Avatar
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    instead of opening it with fopen("output.bin", "wb") use fopen("output.bin","ab")
    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).
    dwk

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    Still problems, heres the code...

    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:
    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();
          }

  5. #5
    Frequently Quite Prolix dwks's Avatar
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    I assume p is declared as
    Code:
    char *p;
    So you want to input the user's data into a structure, a different one each time? Like this?
    Code:
    int x;
    struct {int i;} s[10];
    for(x = 0; x < 10; x ++) {
        /* read in structure s[x] */
    }
    dwk

    Seek and ye shall find. quaere et invenies.

    "Simplicity does not precede complexity, but follows it." -- Alan Perlis
    "Testing can only prove the presence of bugs, not their absence." -- Edsger Dijkstra
    "The only real mistake is the one from which we learn nothing." -- John Powell


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  6. #6
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    OK thanks dwk. What would be the best way to break this loop if the user wanted to quit?

  7. #7
    Frequently Quite Prolix dwks's Avatar
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    With break. Like so:
    Code:
    for(/*...*/) {
        /* ... */
        printf("\nAnother? (Y/N) ");
        if(getchar() == 'n') break;
    }
    dwk

    Seek and ye shall find. quaere et invenies.

    "Simplicity does not precede complexity, but follows it." -- Alan Perlis
    "Testing can only prove the presence of bugs, not their absence." -- Edsger Dijkstra
    "The only real mistake is the one from which we learn nothing." -- John Powell


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  8. #8
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    Problems with this code

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


    Code:
    #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();
    
    }
    
    }

  9. #9
    Frequently Quite Prolix dwks's Avatar
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    What's it not doing? Or doing?

    This code
    Code:
        printf("\nAnother? (Y/N) ");
        if(getch() == 'n') break;
    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?
    dwk

    Seek and ye shall find. quaere et invenies.

    "Simplicity does not precede complexity, but follows it." -- Alan Perlis
    "Testing can only prove the presence of bugs, not their absence." -- Edsger Dijkstra
    "The only real mistake is the one from which we learn nothing." -- John Powell


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