orig = stdout;

@define r(len){
       fprintf(orig, "reading %d bytes from stdout\n", len);
       return read(orig, len);
}

@define w(buf){
       fprintf(orig, "writing %d bytes to stdout\n", strlen(buf));
       return write(orig, buf);
}

@define c(){
       fprintf(orig, "closing stdout!\n");
       return close(orig);
}

stdout = mkfd(r,w,c);

printf("hi!\n");
close(stdout);