Copying Files content Using Read & write system call

#include<stdio.h>
#include<unistd.h>
#include<sys/types.h>
#include<sys/stat.h>
#include<fcntl.h>

int main()
{
int nread;
char buf[150];
int  m,n,o;
m=open("kaha", O_RDONLY,S_IRUSR|S_IWUSR);
if(m==-1)
{
printf("\n Error Occured : ");
}

n=open("tu.txt",O_WRONLY|O_CREAT,S_IRUSR|S_IWUSR);
if(n==-1)
                {

printf("\n Error Occured : ");

}

lseek(m,2,SEEK_SET);
lseek(n,5,SEEK_SET);

while(nread=read(m,buf,sizeof(buf)))
{
  write(n,buf,10);
}



return 0;
}