Thread: binary file help

trying to insert a number 16 into a binary file the binary file contains the following numbers

0,3,6,9,12,15,18,21,24,27

the file must remain sorted and im not allowed to append and resort

my output is

0,3,6,9,12,15,16,18,16,18,16,18,18

here is the code

Code:

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


int main(void)
{
    FILE * fp ; 
    int number ; 
    int numbertemp ; 
    int numbertoinsert = 16 ; 
    
    fp = fopen("numbers_sort.bin" , "r+b" ) ; 
    
    if(fp == NULL)
    {
        printf("Error \n " ) ; 
    }
    
    while(!feof(fp) ) 
    {
        fread(&number , sizeof(int) , 1 , fp ) ; 
        printf("%d\n" , number ) ; 
    }
    
    //read 18 
    fseek(fp , -4*sizeof(int) , SEEK_END) ; 
    fread(&number , sizeof(int) , 1 , fp ) ;
    printf("%d\n" , number ) ; 
    
    //write 16
    fseek(fp , -1*sizeof(int) , SEEK_CUR) ; 
    fwrite(&numbertoinsert , sizeof(int) , 1 , fp ) ;
    fflush(fp);
    //read 21 
    fread(&numbertemp , sizeof(int) , 1 , fp ) ;
    fseek(fp , -1*sizeof(int) , SEEK_CUR) ; 
    
    //write 18
    fwrite(&number , sizeof(int) , 1 , fp ) ;
    fflush(fp);
    //read 24 
    fread(&number , sizeof(int) , 1 , fp ) ;
    fseek(fp , -1*sizeof(int) , SEEK_CUR) ; 
    
    //write 21 
    fwrite(&numbertemp , sizeof(int) , 1 , fp ) ;
    fflush(fp);
    //read 27
    fread(&numbertemp , sizeof(int) , 1 , fp ) ;
    fseek(fp , -1*sizeof(int) , SEEK_CUR) ;
    
    //write 24
    fwrite(&number , sizeof(int) , 1 , fp ) ;
    fflush(fp);
    //write27
    fwrite(&numbertemp , sizeof(int) , 1 , fp ) ;
    fflush(fp);


    printf("after insert \n " ) ; 
    fseek(fp , 0, SEEK_SET) ;
     while(!feof(fp) ) 
    {
        fread(&number , sizeof(int) , 1 , fp ) ; 
        printf("%d\n" , number ) ; 
    }
    
    
    
    getchar() ; 
    
    return 0 ; 
}

what am i doing wrong. i dont see how it can get this output ?

Originally Posted by vart

Obviously - you need some algorithm to insert integer into sorted file

so in pseudocode it would be something like this

Code:

int add_number = ...;
open file
while(read number)
{
    if(add_number < number)
    {
        write add_number;
        add_number = number;
    }
}
write add_number;
close file

so i changed it following you pseudocode
but now i dont get any output at all ?

Code:

int main(void)
{
    FILE * fp ; 
    int number ; 
     
    int numbertoinsert = 16 ; 
    
    fp = fopen("numbers_sort.bin" , "r+b" ) ; 
    
    if(fp == NULL)
    {
        printf("Error \n " ) ; 
    }
    
    while(!feof(fp) ) 
    {
        fread(&number ,sizeof(int) , 1 , fp ) ;
        
        if(numbertoinsert < number )
        {
            fseek(fp , -1*sizeof(int) , SEEK_CUR ) ; 
            fwrite(&numbertoinsert , sizeof(int) , 1  , fp ) ;
            numbertoinsert = number ; 
        }
    }
    fwrite(&numbertoinsert , sizeof(int) , 1  , fp ) ;
    
    fclose(fp) ; 
    
    fp = fopen("numbers_sort.bin" , "rb" ) ; 
    
    if(fp == NULL)
    {
        printf("Error \n " ) ; 
    }
    
    while(!feof(fp) ) 
    {
        fread(&number , sizeof(int) , 1 , fp ) ; 
        printf("%d\n" , number ) ; 
    }
    getchar(); 
    fclose(fp) ; 
    
    return 0 ;
    
}

Thank you that has cleared a lot up. I was convinced it was my compiler.
In main you have

Code:

 return updatefile(16)

I have not seen this before is this to let you know the functions exit status? Ie function returns 0 up success?