fseek in C

fseek() is a standard library function in C Language used to change the file position indicator for a given file stream.

It allows us to move the position within a file to a specified location.

Syntax:

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

"stream": Pointer to a FILE object that identifies the stream.

"offset": Number of bytes to offset from the origin.

"whence": Specifies the starting point for the offset calculation. It can take one of the following values:

SEEK_SET: Beginning of the file.
SEEK_CUR: Current position indicator.
SEEK_END: End of the file.

The "fseek()" function returns 0 if successful, and a non-zero value if an error occurs.

Example: Moving the File Position Indicator to the Beginning of the File

#include <stdio.h>

int main() {
    FILE *file;

    // Open the file in read mode
    file = fopen("example.txt", "r");

    // Check if file opened successfully
    if (file == NULL) {
        perror("Error opening file");
        return 1;
    }

    // Move the file position indicator to the beginning of the file
    if (fseek(file, 0, SEEK_SET) != 0) {
        perror("Error seeking to beginning of file");
        fclose(file);
        return 1;
    }

    // Close the file
    fclose(file);

    return 0;
}

Example: Moving the File Position Indicator Relative to the Current Position

#include <stdio.h>

int main() {
    FILE *file;

    // Open the file in read mode
    file = fopen("example.txt", "r");

    // Check if file opened successfully
    if (file == NULL) {
        perror("Error opening file");
        return 1;
    }

    // Move the file position indicator three bytes forward from the current position
    if (fseek(file, 3, SEEK_CUR) != 0) {
        perror("Error seeking relative to current position");
        fclose(file);
        return 1;
    }

    // Close the file
    fclose(file);

    return 0;
}

Example: Moving the File Position Indicator to the End of the File

#include <stdio.h>

int main() {
    FILE *file;

    // Open the file in read mode
    file = fopen("example.txt", "r");

    // Check if file opened successfully
    if (file == NULL) {
        perror("Error opening file");
        return 1;
    }

    // Move the file position indicator to the end of the file
    if (fseek(file, 0, SEEK_END) != 0) {
        perror("Error seeking to end of file");
        fclose(file);
        return 1;
    }

    // Close the file
    fclose(file);

    return 0;
}

<-- fputs()

rewind() -->