fig19.10

UNIX环境高级编程书的源代码

#include "apue.h"
#include <fcntl.h>

#ifndef _HAS_OPENPT
int
posix_openpt(int oflag)
{
	int		fdm;

	fdm = open("/dev/ptmx", oflag);
	return(fdm);
}
#endif

#ifndef _HAS_PTSNAME
char *
ptsname(int fdm)
{
	int			sminor;
	static char	pts_name[16];

	if (ioctl(fdm, TIOCGPTN, &sminor) < 0)
		return(NULL);
	snprintf(pts_name, sizeof(pts_name), "/dev/pts/%d", sminor);
	return(pts_name);
}
#endif

#ifndef _HAS_GRANTPT
int
grantpt(int fdm)
{
	char			*pts_name;

	pts_name = ptsname(fdm);
	return(chmod(pts_name, S_IRUSR | S_IWUSR | S_IWGRP));
}
#endif

#ifndef _HAS_UNLOCKPT
int
unlockpt(int fdm)
{
	int lock = 0;

	return(ioctl(fdm, TIOCSPTLCK, &lock));
}
#endif

int
ptym_open(char *pts_name, int pts_namesz)
{
	char	*ptr;
	int		fdm;

	/*
	 * Return the name of the master device so that on failure
	 * the caller can print an error message.  Null terminate
	 * to handle case where string length > pts_namesz.
	 */
	strncpy(pts_name, "/dev/ptmx", pts_namesz);
	pts_name[pts_namesz - 1] = '\0';

	fdm = posix_openpt(O_RDWR);
	if (fdm < 0)
		return(-1);
	if (grantpt(fdm) < 0) {		/* grant access to slave */
		close(fdm);
		return(-2);
	}
	if (unlockpt(fdm) < 0) {	/* clear slave's lock flag */
		close(fdm);
		return(-3);
	}
	if ((ptr = ptsname(fdm)) == NULL) {	/* get slave's name */
		close(fdm);
		return(-4);
	}

	/*
	 * Return name of slave.  Null terminate to handle case
	 * where strlen(ptr) > pts_namesz.
	 */
	strncpy(pts_name, ptr, pts_namesz);
	pts_name[pts_namesz - 1] = '\0';
	return(fdm);			/* return fd of master */
}

int
ptys_open(char *pts_name)
{
	int fds;

	if ((fds = open(pts_name, O_RDWR)) < 0)
		return(-5);
	return(fds);
}