ptyopen.c

unix环境高级编程的源代码

#include    <sys/types.h>
#include    <sys/stat.h>
#include    <errno.h>
#include    <fcntl.h>
#include    <grp.h>
#include    "ourhdr.h"

int
ptym_open(char *pts_name)
{
    int        fdm;
    char    *ptr1, *ptr2;

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

                        /* try to open master */
            if ( (fdm = open(pts_name, O_RDWR)) < 0) {
                if (errno == ENOENT)    /* different from EIO */
                    return(-1);            /* out of pty devices */
                else
                    continue;            /* try next pty device */
            }

            pts_name[5] = 't';    /* change "pty" to "tty" */
            return(fdm);        /* got it, return fd of master */
        }
    }
    return(-1);        /* out of pty devices */
}

int
ptys_open(int fdm, char *pts_name)
{
    struct group    *grptr;
    int                gid, fds;

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

            /* following two functions don't work unless we're root */
    chown(pts_name, getuid(), gid);
    chmod(pts_name, S_IRUSR | S_IWUSR | S_IWGRP);

    if ( (fds = open(pts_name, O_RDWR)) < 0) {
        close(fdm);
        return(-1);
    }
    return(fds);
}