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mesg.c
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mesg.c
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/*-
* Copyright (c) 1997 James P. Howard, II <jh@jameshoward.us>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
/*
* Mesg(1) toggles the group-write permissions on a user's tty. An on
* status allows for another user to write to the tty using write(1),
* talk(1), etc.
*/
#include <errno.h>
#include <paths.h>
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/stat.h>
static void help();
int main(int argc, char *argv[])
{
struct stat buf;
int ch, quiet = 0;
char *status = NULL, *tty;
/* Sets the default terminal to the current standards error. */
tty = ttyname(STDERR_FILENO);
while ((ch = getopt(argc, argv, "t:q?")) != EOF)
switch(ch) {
case 'q':
quiet = 1;
break;
case 't':
tty = optarg;
break;
case '?':
help();
/* NOTREACHED */
}
while (--argc != 0)
if (argv[argc][0] != '-' && argv[argc] != tty)
status = argv[argc];
/*
* Moves to the device directory so that calls such as ``mesg -t
* ttyp0'' work without having to prepend the directory name.
*/
(void)chdir(_PATH_DEV);
if(stat(tty, &buf) != 0) {
if(!quiet)
(void)perror(tty);
(void)exit(2);
}
if(status == NULL) {
if(buf.st_mode & S_IWGRP) {
if(!quiet)
(void)fprintf(stderr, "is y\n");
(void)exit(0);
}
if(!quiet)
(void)fprintf(stderr, "is n\n");
(void)exit(1);
}
/* By checking status[0], "y", "yes", "yummy", etc., all are 'y' */
if(status[0] == 'y') {
if(chmod(tty, buf.st_mode | S_IWGRP) != 0) {
if(!quiet)
(void)perror(tty);
(void)exit(2);
}
(void)exit(0);
}
if(status[0] == 'n') {
if(chmod(tty, buf.st_mode & ~S_IWGRP) != 0) {
if(!quiet)
(void)perror(tty);
(void)exit(2);
}
(void)exit(1);
}
/*
* This is only reached if the user entered an invalid parameter
* for the new status of the tty.
*/
(void)exit(2);
}
void help()
{
(void)fprintf(stderr, "\
usage: mesg [-q?] [-t tty] [y | n]\n\
-q -- quiet mode, suppress all output\n\
-t tty -- specify the tty to check/modify\n\
-? -- print this help message\n");
(void)exit(2);
}