write.c revision 1.6
1 /* $NetBSD: write.c,v 1.6 1997/01/17 01:52:12 perry Exp $ */ 2 3 /* 4 * Copyright (c) 1989, 1993 5 * The Regents of the University of California. All rights reserved. 6 * 7 * This code is derived from software contributed to Berkeley by 8 * Jef Poskanzer and Craig Leres of the Lawrence Berkeley Laboratory. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 3. All advertising materials mentioning features or use of this software 19 * must display the following acknowledgement: 20 * This product includes software developed by the University of 21 * California, Berkeley and its contributors. 22 * 4. Neither the name of the University nor the names of its contributors 23 * may be used to endorse or promote products derived from this software 24 * without specific prior written permission. 25 * 26 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 27 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 28 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 29 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 30 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 31 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 32 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 33 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 34 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 35 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 36 * SUCH DAMAGE. 37 */ 38 39 #ifndef lint 40 static char copyright[] = 41 "@(#) Copyright (c) 1989, 1993\n\ 42 The Regents of the University of California. All rights reserved.\n"; 43 #endif /* not lint */ 44 45 #ifndef lint 46 #if 0 47 static char sccsid[] = "@(#)write.c 8.2 (Berkeley) 4/27/95"; 48 #endif 49 static char *rcsid = "$NetBSD: write.c,v 1.6 1997/01/17 01:52:12 perry Exp $"; 50 #endif /* not lint */ 51 52 #include <sys/types.h> 53 #include <sys/param.h> 54 #include <sys/stat.h> 55 #include <ctype.h> 56 #include <stdio.h> 57 #include <string.h> 58 #include <signal.h> 59 #include <time.h> 60 #include <fcntl.h> 61 #include <pwd.h> 62 #include <unistd.h> 63 #include <utmp.h> 64 #include <err.h> 65 66 void done(); 67 void do_write __P((char *, char *, uid_t)); 68 void wr_fputs __P((char *)); 69 void search_utmp __P((char *, char *, char *, uid_t)); 70 int term_chk __P((char *, int *, time_t *, int)); 71 int utmp_chk __P((char *, char *)); 72 73 int 74 main(argc, argv) 75 int argc; 76 char **argv; 77 { 78 register char *cp; 79 time_t atime; 80 uid_t myuid; 81 int msgsok, myttyfd; 82 char tty[MAXPATHLEN], *mytty; 83 84 /* check that sender has write enabled */ 85 if (isatty(fileno(stdin))) 86 myttyfd = fileno(stdin); 87 else if (isatty(fileno(stdout))) 88 myttyfd = fileno(stdout); 89 else if (isatty(fileno(stderr))) 90 myttyfd = fileno(stderr); 91 else 92 errx(1, "can't find your tty"); 93 if (!(mytty = ttyname(myttyfd))) 94 errx(1, "can't find your tty's name"); 95 if (cp = strrchr(mytty, '/')) 96 mytty = cp + 1; 97 if (term_chk(mytty, &msgsok, &atime, 1)) 98 exit(1); 99 if (!msgsok) { 100 (void)fprintf(stderr, 101 "warning: you have write permission turned off; " 102 "no reply possible\n"); 103 } 104 105 myuid = getuid(); 106 107 /* check args */ 108 switch (argc) { 109 case 2: 110 search_utmp(argv[1], tty, mytty, myuid); 111 do_write(tty, mytty, myuid); 112 break; 113 case 3: 114 if (!strncmp(argv[2], "/dev/", 5)) 115 argv[2] += 5; 116 if (utmp_chk(argv[1], argv[2])) 117 errx(1, "%s is not logged in on %s", 118 argv[1], argv[2]); 119 if (term_chk(argv[2], &msgsok, &atime, 1)) 120 exit(1); 121 if (myuid && !msgsok) 122 errx(1, "%s has messages disabled on %s", 123 argv[1], argv[2]); 124 do_write(argv[2], mytty, myuid); 125 break; 126 default: 127 (void)fprintf(stderr, "usage: write user [tty]\n"); 128 exit(1); 129 } 130 done(); 131 /* NOTREACHED */ 132 } 133 134 /* 135 * utmp_chk - checks that the given user is actually logged in on 136 * the given tty 137 */ 138 int 139 utmp_chk(user, tty) 140 char *user, *tty; 141 { 142 struct utmp u; 143 int ufd; 144 145 if ((ufd = open(_PATH_UTMP, O_RDONLY)) < 0) 146 return(0); /* ignore error, shouldn't happen anyway */ 147 148 while (read(ufd, (char *) &u, sizeof(u)) == sizeof(u)) 149 if (strncmp(user, u.ut_name, sizeof(u.ut_name)) == 0 && 150 strncmp(tty, u.ut_line, sizeof(u.ut_line)) == 0) { 151 (void)close(ufd); 152 return(0); 153 } 154 155 (void)close(ufd); 156 return(1); 157 } 158 159 /* 160 * search_utmp - search utmp for the "best" terminal to write to 161 * 162 * Ignores terminals with messages disabled, and of the rest, returns 163 * the one with the most recent access time. Returns as value the number 164 * of the user's terminals with messages enabled, or -1 if the user is 165 * not logged in at all. 166 * 167 * Special case for writing to yourself - ignore the terminal you're 168 * writing from, unless that's the only terminal with messages enabled. 169 */ 170 void 171 search_utmp(user, tty, mytty, myuid) 172 char *user, *tty, *mytty; 173 uid_t myuid; 174 { 175 struct utmp u; 176 time_t bestatime, atime; 177 int ufd, nloggedttys, nttys, msgsok, user_is_me; 178 char atty[UT_LINESIZE + 1]; 179 180 if ((ufd = open(_PATH_UTMP, O_RDONLY)) < 0) 181 err(1, "%s", _PATH_UTMP); 182 183 nloggedttys = nttys = 0; 184 bestatime = 0; 185 user_is_me = 0; 186 while (read(ufd, (char *) &u, sizeof(u)) == sizeof(u)) 187 if (strncmp(user, u.ut_name, sizeof(u.ut_name)) == 0) { 188 ++nloggedttys; 189 (void)strncpy(atty, u.ut_line, UT_LINESIZE); 190 atty[UT_LINESIZE] = '\0'; 191 if (term_chk(atty, &msgsok, &atime, 0)) 192 continue; /* bad term? skip */ 193 if (myuid && !msgsok) 194 continue; /* skip ttys with msgs off */ 195 if (strcmp(atty, mytty) == 0) { 196 user_is_me = 1; 197 continue; /* don't write to yourself */ 198 } 199 ++nttys; 200 if (atime > bestatime) { 201 bestatime = atime; 202 (void)strcpy(tty, atty); 203 } 204 } 205 206 (void)close(ufd); 207 if (nloggedttys == 0) 208 errx(1, "%s is not logged in", user); 209 if (nttys == 0) { 210 if (user_is_me) { /* ok, so write to yourself! */ 211 (void)strcpy(tty, mytty); 212 return; 213 } 214 errx(1, "%s has messages disabled", user); 215 } else if (nttys > 1) 216 warnx("%s is logged in more than once; writing to %s", 217 user, tty); 218 } 219 220 /* 221 * term_chk - check that a terminal exists, and get the message bit 222 * and the access time 223 */ 224 int 225 term_chk(tty, msgsokP, atimeP, showerror) 226 char *tty; 227 int *msgsokP, showerror; 228 time_t *atimeP; 229 { 230 struct stat s; 231 char path[MAXPATHLEN]; 232 233 (void)sprintf(path, "/dev/%s", tty); 234 if (stat(path, &s) < 0) { 235 if (showerror) 236 warn("%s", path); 237 return(1); 238 } 239 *msgsokP = (s.st_mode & (S_IWRITE >> 3)) != 0; /* group write bit */ 240 *atimeP = s.st_atime; 241 return(0); 242 } 243 244 /* 245 * do_write - actually make the connection 246 */ 247 void 248 do_write(tty, mytty, myuid) 249 char *tty, *mytty; 250 uid_t myuid; 251 { 252 register char *login, *nows; 253 register struct passwd *pwd; 254 time_t now; 255 char path[MAXPATHLEN], host[MAXHOSTNAMELEN], line[512]; 256 257 /* Determine our login name before the we reopen() stdout */ 258 if ((login = getlogin()) == NULL) 259 if (pwd = getpwuid(myuid)) 260 login = pwd->pw_name; 261 else 262 login = "???"; 263 264 (void)sprintf(path, "/dev/%s", tty); 265 if ((freopen(path, "w", stdout)) == NULL) 266 err(1, "%s", path); 267 268 (void)signal(SIGINT, done); 269 (void)signal(SIGHUP, done); 270 271 /* print greeting */ 272 if (gethostname(host, sizeof(host)) < 0) 273 (void)strcpy(host, "???"); 274 now = time((time_t *)NULL); 275 nows = ctime(&now); 276 nows[16] = '\0'; 277 (void)printf("\r\n\007\007\007Message from %s@%s on %s at %s ...\r\n", 278 login, host, mytty, nows + 11); 279 280 while (fgets(line, sizeof(line), stdin) != NULL) 281 wr_fputs(line); 282 } 283 284 /* 285 * done - cleanup and exit 286 */ 287 void 288 done() 289 { 290 (void)printf("EOF\r\n"); 291 exit(0); 292 } 293 294 /* 295 * wr_fputs - like fputs(), but makes control characters visible and 296 * turns \n into \r\n 297 */ 298 void 299 wr_fputs(s) 300 register char *s; 301 { 302 register char c; 303 304 #define PUTC(c) if (putchar(c) == EOF) goto err; 305 306 for (; *s != '\0'; ++s) { 307 c = toascii(*s); 308 if (c == '\n') { 309 PUTC('\r'); 310 PUTC('\n'); 311 } else if (!isprint(c) && !isspace(c) && c != '\007') { 312 PUTC('^'); 313 PUTC(c^0x40); /* DEL to ?, others to alpha */ 314 } else 315 PUTC(c); 316 } 317 return; 318 319 err: err(1, NULL); 320 #undef PUTC 321 } 322
Indexes created Thu Sep 25 06:09:39 GMT 2025