Include -Wunreachable-code when building.
[sysvinit.git] / src / dowall.c
1 /*
2 * dowall.c Write to all users on the system.
3 *
4 * Author: Miquel van Smoorenburg, miquels@cistron.nl
5 *
6 * Version: @(#)dowall.c 2.85-5 02-Jul-2003 miquels@cistron.nl
7 *
8 * This file is part of the sysvinit suite,
9 * Copyright (C) 1991-2003 Miquel van Smoorenburg.
10 *
11 * This program is free software; you can redistribute it and/or modify
12 * it under the terms of the GNU General Public License as published by
13 * the Free Software Foundation; either version 2 of the License, or
14 * (at your option) any later version.
15 *
16 * This program is distributed in the hope that it will be useful,
17 * but WITHOUT ANY WARRANTY; without even the implied warranty of
18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
19 * GNU General Public License for more details.
20 *
21 * You should have received a copy of the GNU General Public License
22 * along with this program; if not, write to the Free Software
23 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
24 */
25 #include <sys/types.h>
26 #include <sys/stat.h>
27 #include <sys/sysmacros.h>
28 #include <limits.h>
29 #include <stdlib.h>
30 #include <string.h>
31 #include <time.h>
32 #include <unistd.h>
33 #include <stdio.h>
34 #include <utmp.h>
35 #include <pwd.h>
36 #include <fcntl.h>
37 #include <signal.h>
38 #include <setjmp.h>
39 #include <paths.h>
40
41 #ifndef _PATH_DEV
42 # define _PATH_DEV "/dev/"
43 #endif
44 #ifndef HOST_NAME_MAX
45 # define HOST_NAME_MAX 255
46 #endif
47
48 static sigjmp_buf jbuf;
49
50 /*
51 * Alarm handler
52 */
53 /*ARGSUSED*/
54 # ifdef __GNUC__
55 static void handler(int arg __attribute__((unused)))
56 # else
57 static void handler(int arg)
58 # endif
59 {
60 siglongjmp(jbuf, 1);
61 }
62
63
64 /*
65 * Print a text, escape all characters not in Latin-1.
66 */
67 static void feputs(const char *line, FILE *fp)
68 {
69 unsigned char *p;
70
71 for (p = (unsigned char *)line; *p; p++) {
72 if (strchr("\t\r\n", *p) ||
73 (*p >= 32 && *p <= 127) || (*p >= 160)) {
74 fputc(*p, fp);
75 } else {
76 fprintf(fp, "^%c", (*p & 0x1f) + 'A' - 1);
77 }
78 }
79 fflush(fp);
80 }
81
82
83 static void getuidtty(char **userp, char **ttyp)
84 {
85 struct passwd *pwd;
86 uid_t uid;
87 char *tty;
88 static char uidbuf[32];
89 static char ttynm[UT_LINESIZE + 4];
90 static int init = 0;
91
92 if (!init) {
93
94 uid = getuid();
95 if ((pwd = getpwuid(uid)) != NULL) {
96 uidbuf[0] = 0;
97 strncat(uidbuf, pwd->pw_name, sizeof(uidbuf) - 1);
98 } else {
99 sprintf(uidbuf, uid ? "uid %d" : "root", (int)uid);
100 }
101
102 if ((tty = ttyname(0)) != NULL) {
103 const size_t plen = strlen(_PATH_DEV);
104 if (strncmp(tty, _PATH_DEV, plen) == 0) {
105 tty += plen;
106 if (tty[0] == '/')
107 tty++;
108 }
109 snprintf(ttynm, sizeof(ttynm), "(%.*s) ",
110 UT_LINESIZE, tty);
111 } else
112 ttynm[0] = 0;
113 init++;
114 }
115
116 *userp = uidbuf;
117 *ttyp = ttynm;
118 }
119
120 /*
121 * Check whether given filename looks like tty device.
122 */
123 static int file_isatty(const char *fname)
124 {
125 struct stat st;
126 int major;
127
128 if (stat(fname, &st) < 0)
129 return 0;
130
131 if (st.st_nlink != 1 || !S_ISCHR(st.st_mode))
132 return 0;
133
134 /*
135 * It would be an impossible task to list all major/minors
136 * of tty devices here, so we just exclude the obvious
137 * majors of which just opening has side-effects:
138 * printers and tapes.
139 */
140 major = major(st.st_dev);
141 if (major == 1 || major == 2 || major == 6 || major == 9 ||
142 major == 12 || major == 16 || major == 21 || major == 27 ||
143 major == 37 || major == 96 || major == 97 || major == 206 ||
144 major == 230) return 0;
145
146 return 1;
147 }
148
149 /*
150 * Wall function.
151 */
152 void wall(const char *text, int remote)
153 {
154 FILE *tp;
155 struct sigaction sa;
156 struct utmp *utmp;
157 time_t t;
158 char term[UT_LINESIZE+ strlen(_PATH_DEV) + 1];
159 char line[81];
160 char hostname[HOST_NAME_MAX+1];
161 char *date, *p;
162 char *user, *tty;
163 int fd, flags;
164
165 /*
166 * Make sure tp and fd aren't in a register. Some versions
167 * of gcc clobber those after longjmp (or so I understand).
168 */
169 (void) &tp;
170 (void) &fd;
171
172 getuidtty(&user, &tty);
173
174 /* Get and report current hostname, to make it easier to find
175 out which machine is being shut down. */
176 if (0 != gethostname(hostname, sizeof(hostname))) {
177 strncpy(hostname, "[unknown]", sizeof(hostname)-1);
178 }
179 /* If hostname is truncated, it is unspecified if the string
180 is null terminated or not. Make sure we know it is null
181 terminated. */
182 hostname[sizeof(hostname)-1] = 0;
183
184 /* Get the time */
185 time(&t);
186 date = ctime(&t);
187 for(p = date; *p && *p != '\n'; p++)
188 ;
189 *p = 0;
190
191 if (remote) {
192 snprintf(line, sizeof(line),
193 "\007\r\nRemote broadcast message (%s):\r\n\r\n",
194 date);
195 } else {
196 snprintf(line, sizeof(line),
197 "\007\r\nBroadcast message from %s@%s %s(%s):\r\n\r\n",
198 user, hostname, tty, date);
199 }
200
201 /*
202 * Fork to avoid us hanging in a write()
203 */
204 if (fork() != 0)
205 return;
206
207 memset(&sa, 0, sizeof(sa));
208 sa.sa_handler = handler;
209 sa.sa_flags = 0;
210 sigemptyset(&sa.sa_mask);
211 sigaction(SIGALRM, &sa, NULL);
212
213 setutent();
214
215 while ((utmp = getutent()) != NULL) {
216 if(utmp->ut_type != USER_PROCESS ||
217 utmp->ut_user[0] == 0) continue;
218 if (strncmp(utmp->ut_line, _PATH_DEV, strlen(_PATH_DEV)) == 0) {
219 term[0] = 0;
220 strncat(term, utmp->ut_line, sizeof(term)-1);
221 } else
222 snprintf(term, sizeof(term), _PATH_DEV "%.*s",
223 UT_LINESIZE, utmp->ut_line);
224 if (strstr(term, "/../")) continue;
225
226 fd = -1;
227 tp = NULL;
228
229 /*
230 * Open it non-delay
231 */
232 if (sigsetjmp(jbuf, 1) == 0) {
233 alarm(2);
234 flags = O_WRONLY|O_NDELAY|O_NOCTTY;
235 if (file_isatty(term) &&
236 (fd = open(term, flags)) >= 0) {
237 if (isatty(fd) &&
238 (tp = fdopen(fd, "w")) != NULL) {
239 fputs(line, tp);
240 feputs(text, tp);
241 fflush(tp);
242 }
243 }
244 }
245 alarm(0);
246 if (fd >= 0) close(fd);
247 if (tp != NULL) fclose(tp);
248 }
249 endutent();
250
251 exit(0);
252 }
253