historic/mesg.c

   1 /*
   2  * mesg.c       The "mesg" utility. Gives / restrict access to
   3  *              your terminal by others.
   4  *
   5  * Usage:       mesg [y|n].
   6  *              Without arguments prints out the current settings.
   7  */
   8 #include <stdio.h>
   9 #include <sys/stat.h>
  10 #include <stdlib.h>
  11 #include <errno.h>
  12 #include <unistd.h>
  13
  14 char *Version = "@(#) mesg 1.0 08-12-92 MvS";
  15
  16 int main(int argc, char **argv)
  17 {
  18   struct stat st;
  19
  20   if (!isatty(0)) {
  21         /* Or should we look in /etc/utmp? */
  22         fprintf(stderr, "stdin: is not a tty");
  23         return(1);
  24   }
  25
  26   if (fstat(0, &st) < 0) {
  27         perror("fstat");
  28         return(1);
  29   }
  30   if (argc < 2) {
  31         printf("Is %s\n", ((st.st_mode & 022) == 022) ? "y" : "n");
  32         return(0);
  33   }
  34   if (argc > 2 || (argv[1][0] != 'y' && argv[1][0] != 'n')) {
  35         fprintf(stderr, "Usage: mesg [y|n]\n");
  36         return(1);
  37   }
  38   if (argv[1][0] == 'y')
  39         st.st_mode |= 022;
  40   else
  41         st.st_mode &= ~022;
  42   fchmod(0, st.st_mode);
  43   return(0);
  44 }