Fseek Function in C

The fseek function is a function in the C standard library that changes the position of the file pointer in a stream-oriented file. It is typically used to move the file pointer to a specific location in the file so that subsequent read or write operations will occur at that location. In C, use the fseek() function  to move the file pointer to the desired location and point it  to a specific file location. Once the file pointer has been moved to a given offset, any operation including writing to or reading from the file can be performed as requested by the programmer.

Syntax

Here is the general syntax for using fseek:

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

The stream parameter is a pointer to the file stream you want to modify. The offset parameter is the number of bytes to move the file pointer, and the whence parameter specifies the starting point for the seek operation.

There are three possible values for whence:

1. SEEK_SET: The file pointer is set to the absolute position specified by offset.
2. SEEK_CUR: The file pointer is set to its current position plus the offset value.
3. SEEK_END: The file pointer is set to the end of the file plus the offset value.

For example, to move the file pointer to the beginning of a file, you can use the following code:

fseek(stream, 0, SEEK_SET);

To move the file pointer to the end of the file, you can use the following code:

fseek(stream, 0, SEEK_END);

If the fseek function is successful, it returns 0. If an error occurs, it returns a non-zero value.

We have already seen the syntax of the fseek() function. It takes three arguments: the file pointer, the number of bytes or characters to move, and the position of the file pointer Therefore, fseek() is used in each of the three competitions along with other document functions to perform their respective tasks.

It basically acts as a C function that handles file operations The fopen() function is also built into C and  used to open any file and returns a file pointer. The 'numbytes' function returns the number of bytes from the beginning of the file. The desired read and write operations can be performed by locating and moving the file pointer using the C fseek() function.

The fseek function is typically used in conjunction with other functions from the C standard library, such as fread and fwrite, to perform read and write operations on a file. It allows you to move the file pointer to a specific location in the file so that you can read or write data at that location.One common use of seek is to move the file pointer to a specific location in the file before performing a read or write operation.

Example

Consider the following code:

#include <stdio.h>
int main() {
    // Open a file for reading
    FILE *fp = fopen("myfile.txt", "r");
    // Move the file pointer to the 10th byte of the file
fseek(fp, 10, SEEK_SET);
    // Read the next 10 bytes of the file into a buffer
    char buffer[11];
fread(buffer, 1, 10, fp);
    // Print the buffer
printf("%s\n", buffer);
    // Close the file
fclose(fp);
    return 0;
}

In this example, the file pointer is moved to the 10th byte of the file using fseek, and then the next 10 bytes of the file are read into a buffer using fread. The contents of the buffer are then printed on the screen.

You can also use fseek to write data to a specific location in a file. For example, the following code writes a string to the 10th byte of a file:

#include <stdio.h>
int main() {
    // Open a file for writing
    FILE *fp = fopen("myfile.txt", "w");
    // Move the file pointer to the 10th byte of the file
fseek(fp, 10, SEEK_SET);
    // Write a string to the file
fwrite("Hello, world!", 1, 14, fp);
    // Close the file
fclose(fp);
    return 0;
}

Conclusion

The C fseek() function  and its application in the C language are clearly explained in the previous discussion. Returns a value of zero if the fseek() activity is valid. Otherwise, it returns a non-zero value. Manipulating files is a big part of the C language, so there are many built-in functions such as fopen(), fclose(), getw(), and putw(). Before using a function, we need to know a lot about it to use it properly.