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

int mktmp(char name[], int oflags, int perms) {

   int fd;

   if (sprintf(name, "/tmp/%s%lu", getenv("LOGNAME"),getpid()) <= 0)
      return -1;
   if( (fd = open(name,oflags,perms)) < 0) {
      perror("open");
      return -1;
   }
   unlink(name); 
   return fd ;
}



int main(){
   char tmpfile[256];
   char buffer[80];
   int nr, nw, fd, length;
   length = 0;
   if( (fd = mktmp(tmpfile, O_RDWR | O_CREAT, 0660 ) ) < 0)
         exit(1);

   /* read from stdin to tmpfile: */   
   while( (nr = read(0,buffer,80)) > 0 ) 
      if( (nw = write(fd,buffer,nr) ) < nr) {
          perror("write");
          exit(1);
      } else 
          length += nw;

   if( lseek(fd,0,SEEK_SET) < 0) {
        perror("lseek");
        exit(3);
   }
  
   /* read from tmpfile to stderr: */
   while( (nr = read(fd,buffer,80)) > 0 ) 
      if( (nw = write(2,buffer,nr) ) < nr) {
          perror("write");
          exit(4);
      }

   /* fill buffer with zero's: */
   for(nw=0; nw < 80; nw++)
     buffer[nw] = '0';

   /* now overwrite tmpfile: */
   if( lseek(fd,0,SEEK_SET) < 0) {
        perror("lseek");
        exit(5);
   }
   while( (length >= 80 ) && ( (nw = write(fd,buffer,80)) >0) )
       length -=nw;
   if(write(fd,buffer,length) < 0) {
       perror("write");
       exit(6);
   }
   close(fd); 
   exit(0);
}