posix_spawn_file_actions_adddup2
int posix_spawn_file_actions_adddup2(posix_spawn_file_actions_t *, int, int);
posix_spawn_file_actions_adddup2(&action, stdin_pipe[0], STDIN_FILENO);
posix_spawn_file_actions_adddup2(&action, stdin_pipe[0], STDIN_FILENO);
posix_spawn_file_actions_adddup2(&action, stdin_pipe[0], STDIN_FILENO);
posix_spawn_file_actions_adddup2(&action, stdout_pipe[0],
posix_spawn_file_actions_adddup2(&action, pipefds[0], STDOUT_FILENO);
posix_spawn_file_actions_adddup2(&action, pipefds[0], STDERR_FILENO);
posix_spawn_file_actions_adddup2(&fa, pfd[0], STDIN_FILENO);
posix_spawn_file_actions_adddup2(&fa, fd[1], STDOUT_FILENO);