Modifying a record in C not working

#include <stdio.h>
#include <string.h>
int main()
{
    int tf=0;
    int i=0;
    int j=0;
    char temp[20];
    FILE *fw,*fr;
    char opsn='y';
    char *p;
    int count=0;
    //for writing records into file
    struct student
    {
        char name[20];
        int age;
    }s,s2;
    int recsize=sizeof(s);
    int taka;
    char stnm[20];
    char me[20];
    int ge;
    printf(" \n 1 add ");
    printf(" \n 2 show ");
    printf(" \n 3 modify");
    scanf("%d",&taka);
    if(taka==1)
    {
        fw=fopen("op.txt","a");
        while(opsn=='y')
        {
            count++;
            printf("Enter student name and age\n");
            scanf("%s%d",&s.name,&s.age);
            fprintf(fw,"%s\t%d\n",s.name,s.age);
            printf("Want another record(y|n)\n");
            fflush(stdin);
            opsn=getche();
        }
        fclose(fw);
    }
    if(taka==2)
    {
        //for reading records rom file
        fr=fopen("op.txt","r");
        printf("\nRecord from file is\n");
        i=0;
        while(fscanf(fr,"%s\t%d\n",s.name,&s.age)!=EOF)
        {
            printf("%s %d\n",s.name,s.age);
        }
    }
    //for modifying records rom file
    if(taka==3)
    {
        fr=fopen("op.txt","r+");
        printf("\nEnter name of student to modify");
        scanf("%s",&stnm);
        printf("ok");
        rewind(fr);
        while(fscanf(fr,"%s\t%d\n",&s.name,&s.age)!=EOF)
        {
            if(strcmp(s.name,stnm)==0)
            {
                printf("\nenter new name,age");
                scanf("%s%d",&me,&ge);
                strcpy(s.name,me);
                s.age=ge;
                fseek(fr,recsize,SEEK_SET);
                fprintf(fr,"%s\t%d\n",s.name,s.age);
                break;
            }
            recsize = recsize * tf;
            printf("%s %d  %d\n",s.name,s.age,tf);
            tf++;
        }
        printf(" Done ");
    }
}