File Management - Updating File Records
Following program will allow us to change marks of roll no. 101 using fseek() function. Content of "student.txt" (RollNo, Marks, Name) file is as under:
101 50 AAA
102 60 BBB
103 65 CCC
#include <stdio.h>
int main () {
FILE *fp;
char str[80];
int newmarks;
fp = fopen("student.txt","r+");
printf("Original File Data:\n");
while(fgets(str,80,fp)!=NULL)
printf("%s", str);
//getch();
printf("\n\nEnter new marks of Roll no. 101:");
scanf("%d", &newmarks);
printf("Updated File Data:\n\n");
itoa(newmarks,str, 10); //convert int to string; fputs() write "string" to fp
fseek(fp, 4, 0); //set the pointer to position no. 4
fputs(str, fp); //write string to current position of fp
fclose(fp);
fp = fopen("student.txt","r");
while(fgets(str,80,fp)!=NULL)
printf("%s", str);
fclose(fp);
getch();
return(0);
}
Output of Program
Original File Data:
101 55 AAA
102 60 BBB
103 65 CCC
Enter new marks of Roll no. 101:75
Updated File Data:
101 75 AAA
102 60 BBB
103 65 CCC
