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rcsid[] and sccsid[] and copyright[] are essentially unmaintained (and
unmaintainable).  these days, people use source.  these id's do not provide
any benefit, and do hurt the small install media
(the 33,000 line diff is essentially mechanical)
ok with the idea millert, ok dms

/*	$OpenBSD: wall.c,v 1.25 2009/10/27 23:59:49 deraadt Exp $	*/
/*	$NetBSD: wall.c,v 1.6 1994/11/17 07:17:58 jtc Exp $	*/

/*
 * Copyright (c) 1988, 1990, 1993
 *	The Regents of the University of California.  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.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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.
 */

/*
 * This program is not related to David Wall, whose Stanford Ph.D. thesis
 * is entitled "Mechanisms for Broadcast and Selective Broadcast".
 */

#include <sys/param.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <sys/uio.h>

#include <paths.h>
#include <pwd.h>
#include <grp.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <utmp.h>
#include <vis.h>
#include <err.h>

struct wallgroup {
	gid_t	gid;
	char	*name;
	char	**mem;
	struct wallgroup *next;
} *grouplist;

void	makemsg(char *);
void	addgroup(struct group *, char *);
char   *ttymsg(struct iovec *, int, char *, int);
__dead	void usage(void);

int nobanner;
int mbufsize;
char *mbuf;

/* ARGSUSED */
int
main(int argc, char **argv)
{
	FILE *fp;
	int ch, ingroup;
	struct iovec iov;
	struct utmp utmp;
	char *p, **mem;
	char line[sizeof(utmp.ut_line) + 1];
	char username[sizeof(utmp.ut_name) + 1];
	struct passwd *pw;
	struct group *grp;
	struct wallgroup *g;

	while ((ch = getopt(argc, argv, "ng:")) != -1)
		switch (ch) {
		case 'n':
			/* undoc option for shutdown: suppress banner */
			pw = getpwnam("nobody");
			if (geteuid() == 0 || (pw && getuid() == pw->pw_uid))
				nobanner = 1;
			break;
		case 'g':
			if ((grp = getgrnam(optarg)) == NULL)
				errx(1, "unknown group `%s'", optarg);
			addgroup(grp, optarg);
			break;
		default:
			usage();
		}
	argc -= optind;
	argv += optind;
	if (argc > 1)
		usage();

	makemsg(*argv);

	if (!(fp = fopen(_PATH_UTMP, "r")))
		err(1, "cannot read %s", _PATH_UTMP);
	iov.iov_base = mbuf;
	iov.iov_len = mbufsize;
	/* NOSTRICT */
	while (fread(&utmp, sizeof(utmp), 1, fp) == 1) {
		if (!utmp.ut_name[0])
			continue;
		if (grouplist) {
			ingroup = 0;
			strncpy(username, utmp.ut_name, sizeof(utmp.ut_name));
			username[sizeof(utmp.ut_name)] = '\0';
			pw = getpwnam(username);
			if (!pw)
				continue;
			for (g = grouplist; g && ingroup == 0; g = g->next) {
				if (g->gid == pw->pw_gid)
					ingroup = 1;
				for (mem = g->mem; *mem && ingroup == 0; mem++)
					if (strcmp(username, *mem) == 0)
						ingroup = 1;
			}
			if (ingroup == 0)
				continue;
		}
		strncpy(line, utmp.ut_line, sizeof(utmp.ut_line));
		line[sizeof(utmp.ut_line)] = '\0';
		if ((p = ttymsg(&iov, 1, line, 60*5)) != NULL)
			warnx("%s", p);
	}
	exit(0);
}

void
makemsg(char *fname)
{
	int ch, cnt;
	struct tm *lt;
	struct passwd *pw;
	struct stat sbuf;
	time_t now;
	FILE *fp;
	int fd;
	char *p, *whom, hostname[MAXHOSTNAMELEN], lbuf[100], tmpname[MAXPATHLEN];
	char tmpbuf[5];
	char *ttynam;

	snprintf(tmpname, sizeof(tmpname), "%s/wall.XXXXXXXXXX", _PATH_TMP);
	if ((fd = mkstemp(tmpname)) >= 0) {
		(void)unlink(tmpname);
		fp = fdopen(fd, "r+");
	}
	if (fd == -1 || fp == NULL)
		err(1, "can't open temporary file");

	if (!nobanner) {
		if (!(whom = getlogin()))
			whom = (pw = getpwuid(getuid())) ? pw->pw_name : "???";
		(void)gethostname(hostname, sizeof(hostname));
		(void)time(&now);
		lt = localtime(&now);
		if ((ttynam = ttyname(STDERR_FILENO)) == NULL)
			ttynam = "(not a tty)";

		/*
		 * all this stuff is to blank out a square for the message;
		 * we wrap message lines at column 79, not 80, because some
		 * terminals wrap after 79, some do not, and we can't tell.
		 * Which means that we may leave a non-blank character
		 * in column 80, but that can't be helped.
		 */
		(void)fprintf(fp, "\r%79s\r\n", " ");
		(void)snprintf(lbuf, sizeof lbuf,
		    "Broadcast Message from %s@%s", whom, hostname);
		(void)fprintf(fp, "%-79.79s\007\007\r\n", lbuf);
		(void)snprintf(lbuf, sizeof lbuf,
		    "        (%s) at %d:%02d ...", ttynam,
		    lt->tm_hour, lt->tm_min);
		(void)fprintf(fp, "%-79.79s\r\n", lbuf);
	}
	(void)fprintf(fp, "%79s\r\n", " ");

	if (fname) {
		gid_t egid = getegid();

		setegid(getgid());
		if (freopen(fname, "r", stdin) == NULL)
			err(1, "can't read %s", fname);
		setegid(egid);
	}
	while (fgets(lbuf, sizeof(lbuf), stdin))
		for (cnt = 0, p = lbuf; (ch = *p) != '\0'; ++p, ++cnt) {
			vis(tmpbuf, ch, VIS_SAFE|VIS_NOSLASH, p[1]);
			if (cnt == 79+1-strlen(tmpbuf) || ch == '\n') {
				for (; cnt < 79+1-strlen(tmpbuf); ++cnt)
					putc(' ', fp);
				putc('\r', fp);
				putc('\n', fp);
				cnt = -1;
			}
			if (ch != '\n') {
				int xx;

				for (xx = 0; tmpbuf[xx]; xx++)
					putc(tmpbuf[xx], fp);
			}
		}
	(void)fprintf(fp, "%79s\r\n", " ");
	rewind(fp);

	if (fstat(fd, &sbuf))
		err(1, "can't stat temporary file");
	mbufsize = sbuf.st_size;
	mbuf = malloc((u_int)mbufsize);
	if (mbuf == NULL)
		err(1, NULL);
	if (fread(mbuf, sizeof(*mbuf), mbufsize, fp) != mbufsize)
		err(1, "can't read temporary file");
	(void)close(fd);
}

void
addgroup(struct group *grp, char *name)
{
	int i;
	struct wallgroup *g;

	for (i = 0; grp->gr_mem[i]; i++)
		;

	g = (struct wallgroup *)malloc(sizeof *g);
	if (g == NULL)
		err(1, NULL);
	g->gid = grp->gr_gid;
	g->name = name;
	g->mem = (char **)calloc(i + 1, sizeof(char *));
	if (g->mem == NULL)
		err(1, NULL);
	for (i = 0; grp->gr_mem[i] != NULL; i++) {
		g->mem[i] = strdup(grp->gr_mem[i]);
		if (g->mem[i] == NULL)
			err(1, NULL);
	}
	g->mem[i] = NULL;
	g->next = grouplist;
	grouplist = g;
}

void
usage(void)
{
	extern char *__progname;

	(void)fprintf(stderr, "usage: %s [-g group] [file]\n", __progname);
	exit(1);
}