You must first complete Data File Handling in C before viewing this Lesson

Random Access

There are two predefined functions in C language to provide random access in files:

1. fseek()

fseek() function can be used to take file pointer to a particular position inside a file.

Syntax: fseek(Pointer, Position, Starting);

Pointer is name of file pointer.

Position is number of characters to be jumped.

Staring specifies the position from where file pointer should start. There are three values :

0: Beginning of file.

1: Current position.

2: End of file

Program of fseek() function.

#include<stdio.h>
int main()
{
FILE *f1;
char str[80] , s;
int n;

f1=fopen(“data.txt”,”r”);
fgets(str,80,f1);

printf(“%s”,str);

fseek(f1,2,0);
/*File pointer jumped to 3rd character from beginning*/

s=getc(f);
printf(“\n%c”,s);

fseek(f1,2,1);
/*File pointer jumped to 3rd character from current
position*/

s=getc(f);
printf(“\n%c”,s);

fseek(f1,0,2);
/*File pointer jumped end of file* /

s=getc(f);
printf(“\n%c”,s);

fclose(f);
return(0);
}

Output

Contents of file are=This is file
i
i

This function provides the current file pointer position.

Syntax:

ftell(Pointer)

Pointer is the name of file pointer variable.

Program of ftell() function.

#include<stdio.h>
int main()
{
FILE *f;
char str[50];
char ch;
int n;
f=fopen(“data.txt”,”r”);

fgets(str,50,f);
//To read a string value from a file

printf(“\nContents of file are=”);
printf(“%s”,str);

fseek(f,-1,2);
/*File pointer is placed at the Last character from the
end*/

n=ftell(f);
/*Position of file pointer is stored in variable n.*/

printf(“\nFile pointer is at position %d”,n);
fclose(f);
return(0);
}

Output

Contents of file are=i love india
File pointer is at position 11

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