close_fd
shell_spawn(char *cmd, int stdin_fd, int stdout_fd, int close_fd, pid_t *pidp)
if (close_fd != -1)
err = posix_spawn_file_actions_addclose(&fact, close_fd);
extern int close_fd(FILE *iop);
(void) close_fd(iop);
(void) close_fd(iop);