In C/C++, the fseek() function is used to move the position of the file pointer in the file.

fseek() is used in C language to move the file pointer to a specific location. Offsets and streams are the targets of pointers, and they are given in function parameters. If successful, it returns zero. If unsuccessful, it returns a non-zero value.

The following is the syntax of fseek() in C language:

int fseek(FILE *stream, long int offset, int whence)

Here are the parameters used in fseek():

• stream − This is a pointer used to identify the stream.

• offset − This is the number of bytes starting from the position.

• whence − This is where the offset is added.

whence is specified by one of the following constants.

• SEEK_END − End of file.

• SEEK_SET − Beginning of file.

• SEEK_CUR − The current position of the file pointer.

This is an example of fseek() in C language.

Suppose we have a file called "demo.txt" with the following content:

This is demo text!
This is demo text!
This is demo text!
This is demo text!

Now let's look at the code.

Example

#include<stdio.h>
void main() {
   FILE *f;
   f = fopen("demo.txt", "r");
   if(f == NULL) {
      printf("\n Can&#39;t open file or file doesn&#39;t exist.");
      exit(0);
   }
   fseek(f, 0, SEEK_END);
   printf("The size of file : %ld bytes", ftell(f));
   getch();
}

Output

The size of file : 78 bytes

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