/** \file fd.h exported symbols from fd.c */
+int write_all(int fd, const char *buf, size_t *len);
int file_exists(const char *);
int para_select(int n, fd_set *readfds, fd_set *writefds,
struct timeval *timeout_tv);
size_t *size, int *fd_ptr);
int para_munmap(void *start, size_t length);
int write_ok(int fd);
+void valid_fd_012(void);