commands/mesg/mesg.c

   1 /* mesg - enable or disable communications. Author: John J. Ribera */
   2
   3 /*
   4  * mesg -       enable or disable communications.
   5  *
   6  * Usage:       mesg [ y | n ]
   7  *
   8  *              'mesg n' will turn off group and world permissions of the
   9  *                       user's terminal.
  10  *              'mesg y' will enable group and world to write to the user's
  11  *                       tty.
  12  *              mesg     with no parameters will put the writeable status
  13  *                       onto stdout.
  14  *
  15  * Author:      John J. Ribera, Jr. 09/09/90
  16  */
  17 #include <sys/types.h>
  18 #include <sys/stat.h>
  19 #include <stdio.h>
  20 #include <stdlib.h>
  21 #include <unistd.h>
  22
  23 int main(int argc, char *argv []);
  24
  25 int main(argc, argv)
  26 int  argc;
  27 char *argv[];
  28 {
  29   struct stat statb;
  30   char *tty_name;
  31
  32   if ((tty_name = ttyname(0)) == NULL) exit(2);
  33   if (stat(tty_name, &statb) == -1) exit(2);
  34   if (--argc) {
  35         if (*argv[1] == 'n') statb.st_mode = 0600;
  36           else if (*argv[1] == 'y') statb.st_mode = 0620;
  37           else {
  38                 fprintf(stderr, "mesg: usage: mesg [n|y]\n");
  39                 exit(2);
  40         }
  41         if (chmod(tty_name, statb.st_mode) == -1) exit(2);
  42   } else printf((statb.st_mode & 020) ? "is y\n" : "is n\n");
  43
  44   if (statb.st_mode & 020) exit(0);
  45
  46   exit(1);
  47 }
  48