In this particular demo, we’re going to use some system calls

• A program (user space) can’t read or write files
• A program need to use the system calls which provided by the OS to do this operation (kernel space)

Now first, check the open manual by entering:

man 2 open

If we just type man open it will open a manual for a normal user. So use man 2 open to access the programmer’s manual

Check linux system calls here:

System Calls Implementation

#include <fcntl.h>
#include <stdio.h>
#include <unistd.h>

int main(){

    char msg[50] = "Halo semuanya";
    char buffer[50];
    int fd = open("samples2.txt",O_RDWR);

    printf("fd = %d\\n", fd);

    if (fd != -1) {
        printf("File opened successfully\\n");
        write(fd, msg, sizeof(msg));
        lseek(fd,0,SEEK_SET);
        read(fd, buffer, sizeof(buffer));
        printf("Isi Textnya Adalah: %s\\n", buffer);
        close(fd);

    } 
    else {
        printf("File not found\\nCreating new file\\n");
        fd = open("samples2.txt", O_RDWR | O_CREAT, 0777);
        printf("fd = %d\\n", fd);
        printf("File created successfully\\n");
        write(fd, msg, sizeof(msg));
        lseek(fd,0,SEEK_SET);
        read(fd, buffer, sizeof(buffer));
        printf("Isi Textnya Adalah: %s\\n", buffer);
        close(fd);
        
    }

return 0;
}