int rec_to_delete = 2; // record 3 is index 2 
 
for(int i = 0; i < 9; i++)
{
    if(i != rec_to_delete)
    {
        // copy record
    }
}

 I Think this code will help you to solve your problem:
 
Add Some Student:
 
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<io.h>
#include<fcntl.h>
 
struct student
{
	char name[20];
	char semCode[10];
	int enrollNo;
	int assignSub;
	int marks;
	int attendence;
};
struct student var;
FILE *ptr;
 
void refresh()
{
	fclose(ptr);
	ptr = fopen("c:\\file.txt","a+");
}
void addStudentRecord()
{
	refresh();
	fflush(stdin);
	printf("Enter name:\n");
	gets(var.name);
 
	fflush(stdin);
	printf("Enter Semester Code:\n");
	gets(var.semCode);
 
	fflush(stdin);
	printf("Enter Enrollment Number:\n");
	scanf("%d",&var.enrollNo);
 
	var.assignSub=0;
	var.marks=-1;
 
	fwrite(&var,sizeof(struct student),1,ptr);
 
	printf("Data Entered Successfully\n");
	printf("Press any key..");
	refresh();
	getch();
}
 
When You want to delete the record:
 
void deleteStudentRecord()
{
	int enrollNo;
	int counter=0;
 
 
	FILE *ptr2 = fopen("c:\\file2.txt","a");
 
	int records = getNoOfRecords();
 
	refresh();
	fflush(stdin);
	printf("Enter Enrollment Number:\n");
	scanf("%d",&enrollNo);
 
	while(counter!=records)
	{
		fread(&var,sizeof(struct student),1,ptr);
		if(var.enrollNo==enrollNo)
		{
 
		}
		else
		{
			fwrite(&var,sizeof(struct student),1,ptr2);
		}
		counter++;
	}
	fcloseall();
	remove("c:\\file.txt");
	rename("c:\\file2.txt","c:\\file.txt");
	printf("Press any key..");
	getch();
}
 
void main()
{
	int a=0;
 
	ptr = fopen("c:\\file.txt","a+");
 
	while(a!=2)
	{
		system("cls");
		printf("Select an Option:\n");
		printf("1.Add Student Record\n");
		Printf("2.Delete Student Record\n");
		scanf("%d",&a);
 
		switch(a)
		{
				case 1:
				addStudentRecord();
				break;
 
			case 2:
				updateStudentRecord();
				break;
 
			case 3:
				deleteStudentRecord();
				break;
			default:
				printf("Invalid Option\n");
				break;
		}
}
}
 
2. rename file:
 
rename("c:\\file2.txt","c:\\file.txt");