lib/other/ttyname.c

   1 /* ttyname.c                                            POSIX 4.7.2
   2  *      char *ttyname(int fildes);
   3  *
   4  *      Determines name of a terminal device.
   5  */
   6
   7 #include <lib.h>
   8 #include <sys/stat.h>
   9 #include <dirent.h>
  10 #include <fcntl.h>
  11 #include <stddef.h>
  12 #include <string.h>
  13 #include <unistd.h>
  14
  15 PRIVATE char base[] = "/dev";
  16 PRIVATE char path[sizeof(base) + 1 + NAME_MAX]; /* extra 1 for '/' */
  17
  18 PUBLIC char *ttyname(fildes)
  19 int fildes;
  20 {
  21   DIR *devices;
  22   struct dirent *entry;
  23   struct stat tty_stat;
  24   struct stat dev_stat;
  25
  26   /* Simple first test: file descriptor must be a character device */
  27   if (fstat(fildes, &tty_stat) < 0 || !S_ISCHR(tty_stat.st_mode))
  28         return (char *) NULL;
  29
  30   /* Open device directory for reading  */
  31   if ((devices = opendir(base)) == (DIR *) NULL)
  32         return (char *) NULL;
  33
  34   /* Scan the entries for one that matches perfectly */
  35   while ((entry = readdir(devices)) != (struct dirent *) NULL) {
  36         if (tty_stat.st_ino != entry->d_ino)
  37                 continue;
  38         strcpy(path, base);
  39         strcat(path, "/");
  40         strcat(path, entry->d_name);
  41         if (stat(path, &dev_stat) < 0 || !S_ISCHR(dev_stat.st_mode))
  42                 continue;
  43         if (tty_stat.st_ino == dev_stat.st_ino &&
  44             tty_stat.st_dev == dev_stat.st_dev &&
  45             tty_stat.st_rdev == dev_stat.st_rdev) {
  46                 closedir(devices);
  47                 return path;
  48         }
  49   }
  50
  51   closedir(devices);
  52   return (char *) NULL;
  53 }