Question

Write a function that accepts a handle to a binary file and prints the third last record in the file. The records in the binary file are salaries of employees in a company. Each record is a double (namely each salary is stored as a double). The function prototype is void printThirdLast(FILE *fid);

Answer 1

Please find the below code:

thirdLastRecord.c

#include<stdio.h>
//function declaration
void printThirdLast(FILE *fid);
//main method
int main()
{
   //dclared file pointer
   FILE* file;
   //calling the method
   printThirdLast(file);
  
   return 0;
}

void printThirdLast(FILE *fid)

{
   //storing the file value into array
   double array[1000];
   int i=-1;
   double variable;
       //opening file as read mode
fid = fopen("emp.txt","r");
   //reading line by line
       char line[100];
   while( fgets( line,100,fid ) ){
       if( 1==sscanf(line,"%lf",&variable) ){
       //storing the value into array
           //incrementing the counter
           array[++i]=variable;
          
       }
        else
   puts("variable not valid");
   }
   //printing the third last variable from array
   //i will be last, i-1 will be second last and
   //i-2 will be third last
   printf("Third last record %.02f",array[i-2]);

}

emp.txt

34343.0
534344.0
3546.0
747.98
454.756
456.98
23233.56
123.78
3453.445
2344.67

OUTPUT

Third last record 123.78 Process exited after 0.009781 seconds with return value 0 Press any key to continue - -