fseek() in C/C++ with example

3

fseek() is used to move file pointer associated with a given file to a specific position.
Syntax:

int fseek(FILE *pointer, long int offset, int position)
pointer: pointer to a FILE object that identifies the stream.
offset: number of bytes to offset from position
position: position from where offset is added.

returns:
zero if successful, or else it returns a non-zero value 

position defines the point with respect to which the file pointer needs to be moved. It has three values:
SEEK_END : It denotes end of the file.
SEEK_SET : It denotes starting of the file.
SEEK_CUR : It denotes file pointer’s current position.

// C Program to demonstrate the use of fseek()
#include <stdio.h>

int main()
{
    FILE *fp;
    fp = fopen("test.txt", "r");
    
    // Moving pointer to end
    fseek(fp, 0, SEEK_END);
    
    // Printing position of pointer
    printf("%ld", ftell(fp));

    return 0;
}

Output:

81

Explanation

The file test.txt contains the following text:

"Someone over there is calling you.
we are going for work.
take care of yourself."

When we implement fseek() we move the pointer by 0 distance with respect to end of file i.e pointer now points to end of the file. Therefore the output is 81.

Related article: fseek vs rewind in C

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