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/*
* mesg.c The "mesg" utility. Gives / restrict access to
* your terminal by others.
*
* Usage: mesg [y|n].
* Without arguments prints out the current settings.
*
* This file is part of the sysvinit suite,
* Copyright 1991-1998 Miquel van Smoorenburg.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*/
#include <sys/types.h>
#include <sys/stat.h>
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <unistd.h>
#include <grp.h>
char *Version = "@(#) mesg 2.74 08-Apr-1998 miquels@cistron.nl";
/*
* Here we check if this system has a "tty" group
* for the tty device. If it does, we set the modes
* to -rw--w--- instead if -rw--w--w.
*/
int hasttygrp(struct stat *st)
{
struct group *gr;
if ((gr = getgrgid(st->st_gid)) == NULL)
return 0;
if (strcmp(gr->gr_name, "tty") != 0)
return 0;
return 1;
}
int main(int argc, char **argv)
{
struct stat st;
unsigned int ttymode;
if (!isatty(0)) {
/* Or should we look in /var/run/utmp? */
fprintf(stderr, "stdin: is not a tty\n");
return(1);
}
if (fstat(0, &st) < 0) {
perror("fstat");
return(1);
}
ttymode = hasttygrp(&st) ? 020 : 022;
if (argc < 2) {
printf("is %s\n",
((st.st_mode & ttymode) == ttymode) ? "y" : "n");
return 0;
}
if (argc > 2 || (argv[1][0] != 'y' && argv[1][0] != 'n')) {
fprintf(stderr, "Usage: mesg [y|n]\n");
return 1;
}
if (argv[1][0] == 'y')
st.st_mode |= ttymode;
else
st.st_mode &= ~(ttymode);
fchmod(0, st.st_mode);
return 0;
}
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