#include <errno.h>
#include <unistd.h>

ssize_t r_write(int fd, void *buf, size_t size) {
   char *bufp;
   size_t bytestowrite;
   ssize_t byteswritten;
   size_t totalbytes;

   for (bufp = buf, bytestowrite = size, totalbytes = 0;
        bytestowrite > 0;
        bufp += byteswritten, bytestowrite -= byteswritten) {
      byteswritten = write(fd, bufp, bytestowrite);
      if ((byteswritten == -1) && (errno != EINTR))
         return -1;
      if (byteswritten == -1)
         byteswritten = 0;
      totalbytes += byteswritten;
   }
   return totalbytes;
}