Notes

#include <stdio.h>
#include <fcntl.h> // For open()
#include <unistd.h> // For lseek(), read(), write(), close()
#include <string.h> // For strlen
#include <errno.h> // For perror

int main() {
// Open the file for reading and writing
int fd = open("file_io_test.txt", O_RDWR);
if (fd == -1) {
perror("Error opening file");
return 1;
}

// Move file pointer to the 20th byte
if (lseek(fd, 20, SEEK_SET) == -1) {
perror("Error seeking in file");
close(fd);
return 1;
}

// Write last name and first name
char name[] = "Abdul Khaliq Umer";
if (write(fd, name, strlen(name)) == -1) {
perror("Error writing to file");
close(fd);
return 1;
}

// Move back to the beginning of the file
if (lseek(fd, 0, SEEK_SET) == -1) {
perror("Error seeking to start of file");
close(fd);
return 1;
}

// Read the file content and display it
char buffer[1024];
ssize_t bytes_read = read(fd, buffer, sizeof(buffer) - 1);
if (bytes_read == -1) {
perror("Error reading from file");
close(fd);
return 1;
}

// Null-terminate the buffer and print it
buffer[bytes_read] = '';
printf("File content:n%sn", buffer);

// Close the file descriptor
if (close(fd) == -1) {
perror("Error closing file");
return 1;
}

return 0;
}