write.c revision 1.2
1 /* 2 * Copyright (c) 1989 The Regents of the University of California. 3 * All rights reserved. 4 * 5 * This code is derived from software contributed to Berkeley by 6 * Jef Poskanzer and Craig Leres of the Lawrence Berkeley Laboratory. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. All advertising materials mentioning features or use of this software 17 * must display the following acknowledgement: 18 * This product includes software developed by the University of 19 * California, Berkeley and its contributors. 20 * 4. Neither the name of the University nor the names of its contributors 21 * may be used to endorse or promote products derived from this software 22 * without specific prior written permission. 23 * 24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 27 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 34 * SUCH DAMAGE. 35 */ 36 37 #ifndef lint 38 char copyright[] = 39 "@(#) Copyright (c) 1989 The Regents of the University of California.\n\ 40 All rights reserved.\n"; 41 #endif /* not lint */ 42 43 #ifndef lint 44 /*static char sccsid[] = "from: @(#)write.c 4.22 (Berkeley) 6/1/90";*/ 45 static char rcsid[] = "$Id: write.c,v 1.2 1993/08/01 18:01:05 mycroft Exp $"; 46 #endif /* not lint */ 47 48 #include <sys/param.h> 49 #include <sys/signal.h> 50 #include <sys/stat.h> 51 #include <sys/file.h> 52 #include <sys/time.h> 53 #include <utmp.h> 54 #include <ctype.h> 55 #include <pwd.h> 56 #include <stdio.h> 57 #include <string.h> 58 59 extern int errno; 60 61 main(argc, argv) 62 int argc; 63 char **argv; 64 { 65 register char *cp; 66 time_t atime; 67 uid_t myuid; 68 int msgsok, myttyfd; 69 char tty[MAXPATHLEN], *mytty, *ttyname(); 70 void done(); 71 72 /* check that sender has write enabled */ 73 if (isatty(fileno(stdin))) 74 myttyfd = fileno(stdin); 75 else if (isatty(fileno(stdout))) 76 myttyfd = fileno(stdout); 77 else if (isatty(fileno(stderr))) 78 myttyfd = fileno(stderr); 79 else { 80 (void)fprintf(stderr, "write: can't find your tty\n"); 81 exit(1); 82 } 83 if (!(mytty = ttyname(myttyfd))) { 84 (void)fprintf(stderr, "write: can't find your tty's name\n"); 85 exit(1); 86 } 87 if (cp = rindex(mytty, '/')) 88 mytty = cp + 1; 89 if (term_chk(mytty, &msgsok, &atime, 1)) 90 exit(1); 91 if (!msgsok) { 92 (void)fprintf(stderr, 93 "write: you have write permission turned off.\n"); 94 exit(1); 95 } 96 97 myuid = getuid(); 98 99 /* check args */ 100 switch (argc) { 101 case 2: 102 search_utmp(argv[1], tty, mytty, myuid); 103 do_write(tty, mytty, myuid); 104 break; 105 case 3: 106 if (!strncmp(argv[2], "/dev/", 5)) 107 argv[2] += 5; 108 if (utmp_chk(argv[1], argv[2])) { 109 (void)fprintf(stderr, 110 "write: %s is not logged in on %s.\n", 111 argv[1], argv[2]); 112 exit(1); 113 } 114 if (term_chk(argv[2], &msgsok, &atime, 1)) 115 exit(1); 116 if (myuid && !msgsok) { 117 (void)fprintf(stderr, 118 "write: %s has messages disabled on %s\n", 119 argv[1], argv[2]); 120 exit(1); 121 } 122 do_write(argv[2], mytty, myuid); 123 break; 124 default: 125 (void)fprintf(stderr, "usage: write user [tty]\n"); 126 exit(1); 127 } 128 done(); 129 /* NOTREACHED */ 130 } 131 132 /* 133 * utmp_chk - checks that the given user is actually logged in on 134 * the given tty 135 */ 136 utmp_chk(user, tty) 137 char *user, *tty; 138 { 139 struct utmp u; 140 int ufd; 141 142 if ((ufd = open(_PATH_UTMP, O_RDONLY)) < 0) 143 return(0); /* ignore error, shouldn't happen anyway */ 144 145 while (read(ufd, (char *) &u, sizeof(u)) == sizeof(u)) 146 if (strncmp(user, u.ut_name, sizeof(u.ut_name)) == 0 && 147 strncmp(tty, u.ut_line, sizeof(u.ut_line)) == 0) { 148 (void)close(ufd); 149 return(0); 150 } 151 152 (void)close(ufd); 153 return(1); 154 } 155 156 /* 157 * search_utmp - search utmp for the "best" terminal to write to 158 * 159 * Ignores terminals with messages disabled, and of the rest, returns 160 * the one with the most recent access time. Returns as value the number 161 * of the user's terminals with messages enabled, or -1 if the user is 162 * not logged in at all. 163 * 164 * Special case for writing to yourself - ignore the terminal you're 165 * writing from, unless that's the only terminal with messages enabled. 166 */ 167 search_utmp(user, tty, mytty, myuid) 168 char *user, *tty, *mytty; 169 uid_t myuid; 170 { 171 struct utmp u; 172 time_t bestatime, atime; 173 int ufd, nloggedttys, nttys, msgsok, user_is_me; 174 char atty[UT_LINESIZE + 1]; 175 176 if ((ufd = open(_PATH_UTMP, O_RDONLY)) < 0) { 177 perror("utmp"); 178 exit(1); 179 } 180 181 nloggedttys = nttys = 0; 182 bestatime = 0; 183 user_is_me = 0; 184 while (read(ufd, (char *) &u, sizeof(u)) == sizeof(u)) 185 if (strncmp(user, u.ut_name, sizeof(u.ut_name)) == 0) { 186 ++nloggedttys; 187 (void)strncpy(atty, u.ut_line, UT_LINESIZE); 188 atty[UT_LINESIZE] = '\0'; 189 if (term_chk(atty, &msgsok, &atime, 0)) 190 continue; /* bad term? skip */ 191 if (myuid && !msgsok) 192 continue; /* skip ttys with msgs off */ 193 if (strcmp(atty, mytty) == 0) { 194 user_is_me = 1; 195 continue; /* don't write to yourself */ 196 } 197 ++nttys; 198 if (atime > bestatime) { 199 bestatime = atime; 200 (void)strcpy(tty, atty); 201 } 202 } 203 204 (void)close(ufd); 205 if (nloggedttys == 0) { 206 (void)fprintf(stderr, "write: %s is not logged in\n", user); 207 exit(1); 208 } 209 if (nttys == 0) { 210 if (user_is_me) { /* ok, so write to yourself! */ 211 (void)strcpy(tty, mytty); 212 return; 213 } 214 (void)fprintf(stderr, 215 "write: %s has messages disabled\n", user); 216 exit(1); 217 } else if (nttys > 1) { 218 (void)fprintf(stderr, 219 "write: %s is logged in more than once; writing to %s\n", 220 user, tty); 221 } 222 } 223 224 /* 225 * term_chk - check that a terminal exists, and get the message bit 226 * and the access time 227 */ 228 term_chk(tty, msgsokP, atimeP, showerror) 229 char *tty; 230 int *msgsokP, showerror; 231 time_t *atimeP; 232 { 233 struct stat s; 234 char path[MAXPATHLEN]; 235 236 (void)sprintf(path, "/dev/%s", tty); 237 if (stat(path, &s) < 0) { 238 if (showerror) 239 (void)fprintf(stderr, 240 "write: %s: %s\n", path, strerror(errno)); 241 return(1); 242 } 243 *msgsokP = (s.st_mode & (S_IWRITE >> 3)) != 0; /* group write bit */ 244 *atimeP = s.st_atime; 245 return(0); 246 } 247 248 /* 249 * do_write - actually make the connection 250 */ 251 do_write(tty, mytty, myuid) 252 char *tty, *mytty; 253 uid_t myuid; 254 { 255 register char *login, *nows; 256 register struct passwd *pwd; 257 time_t now, time(); 258 char *getlogin(), path[MAXPATHLEN], host[MAXHOSTNAMELEN], line[512]; 259 void done(); 260 261 /* Determine our login name before the we reopen() stdout */ 262 if ((login = getlogin()) == NULL) 263 if (pwd = getpwuid(myuid)) 264 login = pwd->pw_name; 265 else 266 login = "???"; 267 268 (void)sprintf(path, "/dev/%s", tty); 269 if ((freopen(path, "w", stdout)) == NULL) { 270 (void)fprintf(stderr, "write: %s: %s\n", path, strerror(errno)); 271 exit(1); 272 } 273 274 (void)signal(SIGINT, done); 275 (void)signal(SIGHUP, done); 276 277 /* print greeting */ 278 if (gethostname(host, sizeof(host)) < 0) 279 (void)strcpy(host, "???"); 280 now = time((time_t *)NULL); 281 nows = ctime(&now); 282 nows[16] = '\0'; 283 (void)printf("\r\n\007\007\007Message from %s@%s on %s at %s ...\r\n", 284 login, host, mytty, nows + 11); 285 286 while (fgets(line, sizeof(line), stdin) != NULL) 287 wr_fputs(line); 288 } 289 290 /* 291 * done - cleanup and exit 292 */ 293 void 294 done() 295 { 296 (void)printf("EOF\r\n"); 297 exit(0); 298 } 299 300 /* 301 * wr_fputs - like fputs(), but makes control characters visible and 302 * turns \n into \r\n 303 */ 304 wr_fputs(s) 305 register char *s; 306 { 307 register char c; 308 309 #define PUTC(c) if (putchar(c) == EOF) goto err; 310 311 for (; *s != '\0'; ++s) { 312 c = toascii(*s); 313 if (c == '\n') { 314 PUTC('\r'); 315 PUTC('\n'); 316 } else if (!isprint(c) && !isspace(c) && c != '\007') { 317 PUTC('^'); 318 PUTC(c^0x40); /* DEL to ?, others to alpha */ 319 } else 320 PUTC(c); 321 } 322 return; 323 324 err: (void)fprintf(stderr, "write: %s\n", strerror(errno)); 325 exit(1); 326 #undef PUTC 327 } 328
Indexes created Tue Sep 30 20:09:53 GMT 2025