modify.c

//program to modify the record in a file

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

int main(void)
{
    struct record
    {
        char name[20];
        int roll;
        int marks;
    } student;
    FILE *fp;
    char name[20];
    long size = sizeof(student);
    unsigned flag = 0;

    fp = fopen("stu", "rb+");
    if (fp == NULL)
    {
        printf("Error in openning file\n");
        exit(1);
    }
    printf("Enter the name  of student whose record is to be modified : ");
    scanf("%s", name);
    while (fread(&student, sizeof(student), 1, fp) == 1)
        if (strcmp(student.name, name) == 0)
        {
            printf("Enter new date -->\n");
            printf("Enter name : ");
            scanf("%s", student.name);
            printf("Enter roll no : ");
            scanf("%d", &student.roll);
            printf("Enter marks: ");
            scanf("%d", &student.marks);
            fseek(fp, -size, 1);
            fwrite(&student, sizeof(student), 1, fp);
            flag = 1;
            break;
        }
    if (flag == 0)
        printf("Name not found in file\n");
    else
        printf("Record Modified........\n");
    fclose(fp);
    return 0;
}