tmp.c

#include <sys/types.h>
#include <unistd.h>
#include <fcntl.h>
   int fdin, fdout, retval;
   char buf[2048];
   ssize_t nread, nwrote;
   fdin = open("readfile", O_RDONLY);
   fdout = open("writefile", O_CREAT | O_WRONLY, 0644);
   nread = read(fdin, buf, 2048);
   nwrote = write(fdout, buf, (size_t)nread);
   retval = close(fdin);
   retval = close(fdout);
  // (calls can fail!!, read man pages and /usr/include/fcntl.h, also think
  // of copying a file larger than 2048 bytes - try buffer at a time till done!)