minopen.c

Runs a shell on the first unused tty。。。

/* minopen.c - Runs a shell on the first unused tty */

#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <signal.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <sys/vt.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/wait.h>

int main (int argc, const char **argv) {
    int vtnum;
    int vtfd;
    struct vt_stat vtstat;
    char device[32];
    int child;

    vtfd = open("/dev/tty", O_RDWR, 0);
    if (vtfd < 0) {
        perror("minopen: could not open /dev/tty");
        exit (1);
    }
    if (ioctl(vtfd, VT_GETSTATE, &vtstat) < 0) {
        perror("minopen: tty is not virtual console");
        exit (1);
    }
    if (ioctl(vtfd, VT_OPENQRY, &vtnum) < 0) {
        perror("minopen: no free virtual consoles");
        exit (1);
    }
    sprintf(device, "/dev/tty%d", vtnum);
    if (access(device, (W_OK|R_OK)) < 0) {
        perror("minopen: insufficient permission on tty");
        exit (1);
    }
    child = fork();
    if (child == 0) {
        ioctl(vtfd, VT_ACTIVATE, vtnum);
        ioctl(vtfd, VT_WAITACTIVE, vtnum);
        setsid();
        close (0); close (1); close (2);
        close (vtfd);
        vtfd = open(device, O_RDWR, 0); dup(vtfd); dup(vtfd);
        execlp("/bin/bash", "bash", NULL);
    }
    wait (&child);
    ioctl(vtfd, VT_ACTIVATE, vtstat.v_active);
    ioctl(vtfd, VT_WAITACTIVE, vtstat.v_active);
    ioctl(vtfd, VT_DISALLOCATE, vtnum);
    exit(0);
}