-int file_exists(const char *);
-int para_exec(pid_t *, const char *, char *const [], int *);
-int para_exec_cmdline_pid(pid_t *, char *, int *);
-
-/* signal */
-int para_signal_init(void);
-int para_install_sighandler(int);
-void para_reap_children(void);
-pid_t para_reap_child(void);
-int para_next_signal(void);