bsd_ptyopen.c

UNIX环境高级编程第二版（英文版）配书的源代码

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

#ifndef _HAS_OPENPT
int
posix_openpt(int oflag)
{
	int		fdm;
	char	*ptr1, *ptr2;
	char	ptm_name[16];

	strcpy(ptm_name, "/dev/ptyXY");
	/* array index:   0123456789   (for references in following code) */
	for (ptr1 = "pqrstuvwxyzPQRST"; *ptr1 != 0; ptr1++) {
		ptm_name[8] = *ptr1;
		for (ptr2 = "0123456789abcdef"; *ptr2 != 0; ptr2++) {
			ptm_name[9] = *ptr2;

			/*
			 * Try to open the master.
			 */
			if ((fdm = open(ptm_name, oflag)) < 0) {
				if (errno == ENOENT)	/* different from EIO */
					return(-1);			/* out of pty devices */
				else
					continue;			/* try next pty device */
			}
			return(fdm);		/* got it, return fd of master */
		}
	}
	errno = EAGAIN;
	return(-1);		/* out of pty devices */
}
#endif

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

	ptm_name = ttyname(fdm);
	if (ptm_name == NULL)
		return(NULL);
	strncpy(pts_name, ptm_name, sizeof(pts_name));
	pts_name[sizeof(pts_name) - 1] = '\0';
	if (strncmp(pts_name, "/dev/pty/", 9) == 0)
		pts_name[9] = 's';	/* change /dev/pty/mXX to /dev/pty/sXX */
	else
		pts_name[5] = 't';	/* change "pty" to "tty" */
	return(pts_name);
}
#endif

#ifndef _HAS_GRANTPT
int
grantpt(int fdm)
{
	struct group	*grptr;
	int				gid;
	char			*pts_name;

	pts_name = ptsname(fdm);
	if ((grptr = getgrnam("tty")) != NULL)
		gid = grptr->gr_gid;
	else
		gid = -1;		/* group tty is not in the group file */

	/*
	 * The following two calls won't work unless we're the superuser.
	 */
	if (chown(pts_name, getuid(), gid) < 0)
		return(-1);
	return(chmod(pts_name, S_IRUSR | S_IWUSR | S_IWGRP));
}
#endif

#ifndef _HAS_UNLOCKPT
int
unlockpt(int fdm)
{
	return(0); /* nothing to do */
}
#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/ptyXX", pts_namesz);
	pts_name[pts_namesz - 1] = '\0';
	if ((fdm = posix_openpt(O_RDWR)) < 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);
}