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#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <sys/ioctl.h>
#include <linux/kd.h>
#include "getfd.h"
/*
* getfd.c
*
* Get an fd for use with kbd/console ioctls.
* We try several things because opening /dev/console will fail
* if someone else used X (which does a chown on /dev/console).
*/
static int
is_a_console(int fd) {
char arg;
arg = 0;
return (ioctl(fd, KDGKBTYPE, &arg) == 0
&& ((arg == KB_101) || (arg == KB_84)));
}
static int
open_a_console(const char *fnam) {
int fd;
/*
* For ioctl purposes we only need some fd and permissions
* do not matter. But setfont:activatemap() does a write.
*/
fd = open(fnam, O_RDWR);
if (fd < 0 && errno == EACCES)
fd = open(fnam, O_WRONLY);
if (fd < 0 && errno == EACCES)
fd = open(fnam, O_RDONLY);
if (fd < 0)
return -1;
if (!is_a_console(fd)) {
close(fd);
return -1;
}
return fd;
}
int getfd(const char *fnam) {
int fd;
if (fnam) {
fd = open_a_console(fnam);
if (fd >= 0)
return fd;
fprintf(stderr,
("Couldnt open %s\n"), fnam);
exit(1);
}
fd = open_a_console("/dev/tty");
if (fd >= 0)
return fd;
fd = open_a_console("/dev/tty0");
if (fd >= 0)
return fd;
fd = open_a_console("/dev/vc/0");
if (fd >= 0)
return fd;
fd = open_a_console("/dev/console");
if (fd >= 0)
return fd;
for (fd = 0; fd < 3; fd++)
if (is_a_console(fd))
return fd;
fprintf(stderr,
("Couldnt get a file descriptor referring to the console\n"));
exit(1); /* total failure */
}
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