なんちゃってpty関数

#include <stdlib.h>

int openpty(int *amaster, int *aslave, char *name, struct termios *termp, struct winsize *winp) {
	int master, slave;
	char name_slave[256];

	master = open("/dev/ptmx", O_RDWR | O_NONBLOCK);
	if (master == -1) {
		return -1;
	}

	if (grantpt(master)) {
		close(master);
		return -1;
	}

	if (unlockpt(master)) {
		close(master);
		return -1;
	}

	strcpy(name_slave, ptsname(master));
	slave = open(name_slave, O_RDWR | O_NOCTTY);
	if (slave == -1) {
		close(master);
		return -1;
	}

	*amaster = master;
	*aslave = slave;

	return 0;
}

pid_t forkpty(int *master, char *name, struct termios *tio, struct winsize *ws) {
	int slave;
	pid_t pid;

	if (openpty(master, &slave, NULL, NULL, NULL) == -1) {
		return -1;
	}

	pid = fork();
	if (pid < 0) {
		return -1;
	} else if (pid == 0) {	//child
		close(*master);
		setsid();
		dup2(slave, 0);
		dup2(slave, 1);
		dup2(slave, 2);
		if (slave > 2) {
			close(slave);
		}
		return 0;
	}

	//parent
	close(slave);
	return pid;
}