a_fileno
int a_fileno; /* file number */
return content_encoding_by_fileno(ap->a_fileno, ctype);
return content_type_by_fileno(ap->a_fileno);
fi = Fdopen(ap->a_fileno, "ref");
err(EXIT_FAILURE, "Fdopen: %d", ap->a_fileno);
map.a_fileno = fileno(fi);