write.c revision 1.4
1 /* 2 * Copyright (c) 1989, 1993 3 * The Regents of the University of California. 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 static char copyright[] = 39 "@(#) Copyright (c) 1989, 1993\n\ 40 The Regents of the University of California. All rights reserved.\n"; 41 #endif /* not lint */ 42 43 #ifndef lint 44 /*static char sccsid[] = "from: @(#)write.c 8.1 (Berkeley) 6/6/93";*/ 45 static char *rcsid = "$Id: write.c,v 1.4 1994/12/21 07:11:00 jtc Exp $"; 46 #endif /* not lint */ 47 48 #include <sys/types.h> 49 #include <sys/param.h> 50 #include <sys/stat.h> 51 #include <ctype.h> 52 #include <stdio.h> 53 #include <string.h> 54 #include <signal.h> 55 #include <time.h> 56 #include <fcntl.h> 57 #include <pwd.h> 58 #include <unistd.h> 59 #include <utmp.h> 60 #include <err.h> 61 62 void done(); 63 void do_write __P((char *, char *, uid_t)); 64 void wr_fputs __P((char *)); 65 void search_utmp __P((char *, char *, char *, uid_t)); 66 int term_chk __P((char *, int *, time_t *, int)); 67 int utmp_chk __P((char *, char *)); 68 69 int 70 main(argc, argv) 71 int argc; 72 char **argv; 73 { 74 register char *cp; 75 time_t atime; 76 uid_t myuid; 77 int msgsok, myttyfd; 78 char tty[MAXPATHLEN], *mytty; 79 80 /* check that sender has write enabled */ 81 if (isatty(fileno(stdin))) 82 myttyfd = fileno(stdin); 83 else if (isatty(fileno(stdout))) 84 myttyfd = fileno(stdout); 85 else if (isatty(fileno(stderr))) 86 myttyfd = fileno(stderr); 87 else 88 errx(1, "can't find your tty"); 89 if (!(mytty = ttyname(myttyfd))) 90 errx(1, "can't find your tty's name"); 91 if (cp = strrchr(mytty, '/')) 92 mytty = cp + 1; 93 if (term_chk(mytty, &msgsok, &atime, 1)) 94 exit(1); 95 if (!msgsok) 96 errx(1, "you have write permission turned off"); 97 98 myuid = getuid(); 99 100 /* check args */ 101 switch (argc) { 102 case 2: 103 search_utmp(argv[1], tty, mytty, myuid); 104 do_write(tty, mytty, myuid); 105 break; 106 case 3: 107 if (!strncmp(argv[2], "/dev/", 5)) 108 argv[2] += 5; 109 if (utmp_chk(argv[1], argv[2])) 110 errx(1, "%s is not logged in on %s", 111 argv[1], argv[2]); 112 if (term_chk(argv[2], &msgsok, &atime, 1)) 113 exit(1); 114 if (myuid && !msgsok) 115 errx(1, "%s has messages disabled on %s", 116 argv[1], argv[2]); 117 do_write(argv[2], mytty, myuid); 118 break; 119 default: 120 (void)fprintf(stderr, "usage: write user [tty]\n"); 121 exit(1); 122 } 123 done(); 124 /* NOTREACHED */ 125 } 126 127 /* 128 * utmp_chk - checks that the given user is actually logged in on 129 * the given tty 130 */ 131 int 132 utmp_chk(user, tty) 133 char *user, *tty; 134 { 135 struct utmp u; 136 int ufd; 137 138 if ((ufd = open(_PATH_UTMP, O_RDONLY)) < 0) 139 return(0); /* ignore error, shouldn't happen anyway */ 140 141 while (read(ufd, (char *) &u, sizeof(u)) == sizeof(u)) 142 if (strncmp(user, u.ut_name, sizeof(u.ut_name)) == 0 && 143 strncmp(tty, u.ut_line, sizeof(u.ut_line)) == 0) { 144 (void)close(ufd); 145 return(0); 146 } 147 148 (void)close(ufd); 149 return(1); 150 } 151 152 /* 153 * search_utmp - search utmp for the "best" terminal to write to 154 * 155 * Ignores terminals with messages disabled, and of the rest, returns 156 * the one with the most recent access time. Returns as value the number 157 * of the user's terminals with messages enabled, or -1 if the user is 158 * not logged in at all. 159 * 160 * Special case for writing to yourself - ignore the terminal you're 161 * writing from, unless that's the only terminal with messages enabled. 162 */ 163 void 164 search_utmp(user, tty, mytty, myuid) 165 char *user, *tty, *mytty; 166 uid_t myuid; 167 { 168 struct utmp u; 169 time_t bestatime, atime; 170 int ufd, nloggedttys, nttys, msgsok, user_is_me; 171 char atty[UT_LINESIZE + 1]; 172 173 if ((ufd = open(_PATH_UTMP, O_RDONLY)) < 0) 174 err(1, "%s", _PATH_UTMP); 175 176 nloggedttys = nttys = 0; 177 bestatime = 0; 178 user_is_me = 0; 179 while (read(ufd, (char *) &u, sizeof(u)) == sizeof(u)) 180 if (strncmp(user, u.ut_name, sizeof(u.ut_name)) == 0) { 181 ++nloggedttys; 182 (void)strncpy(atty, u.ut_line, UT_LINESIZE); 183 atty[UT_LINESIZE] = '\0'; 184 if (term_chk(atty, &msgsok, &atime, 0)) 185 continue; /* bad term? skip */ 186 if (myuid && !msgsok) 187 continue; /* skip ttys with msgs off */ 188 if (strcmp(atty, mytty) == 0) { 189 user_is_me = 1; 190 continue; /* don't write to yourself */ 191 } 192 ++nttys; 193 if (atime > bestatime) { 194 bestatime = atime; 195 (void)strcpy(tty, atty); 196 } 197 } 198 199 (void)close(ufd); 200 if (nloggedttys == 0) 201 errx(1, "%s is not logged in", user); 202 if (nttys == 0) { 203 if (user_is_me) { /* ok, so write to yourself! */ 204 (void)strcpy(tty, mytty); 205 return; 206 } 207 errx(1, "%s has messages disabled", user); 208 } else if (nttys > 1) 209 warnx("%s is logged in more than once; writing to %s", 210 user, tty); 211 } 212 213 /* 214 * term_chk - check that a terminal exists, and get the message bit 215 * and the access time 216 */ 217 int 218 term_chk(tty, msgsokP, atimeP, showerror) 219 char *tty; 220 int *msgsokP, showerror; 221 time_t *atimeP; 222 { 223 struct stat s; 224 char path[MAXPATHLEN]; 225 226 (void)sprintf(path, "/dev/%s", tty); 227 if (stat(path, &s) < 0) { 228 if (showerror) 229 warn("%s", path); 230 return(1); 231 } 232 *msgsokP = (s.st_mode & (S_IWRITE >> 3)) != 0; /* group write bit */ 233 *atimeP = s.st_atime; 234 return(0); 235 } 236 237 /* 238 * do_write - actually make the connection 239 */ 240 void 241 do_write(tty, mytty, myuid) 242 char *tty, *mytty; 243 uid_t myuid; 244 { 245 register char *login, *nows; 246 register struct passwd *pwd; 247 time_t now; 248 char path[MAXPATHLEN], host[MAXHOSTNAMELEN], line[512]; 249 250 /* Determine our login name before the we reopen() stdout */ 251 if ((login = getlogin()) == NULL) 252 if (pwd = getpwuid(myuid)) 253 login = pwd->pw_name; 254 else 255 login = "???"; 256 257 (void)sprintf(path, "/dev/%s", tty); 258 if ((freopen(path, "w", stdout)) == NULL) 259 err(1, "%s", path); 260 261 (void)signal(SIGINT, done); 262 (void)signal(SIGHUP, done); 263 264 /* print greeting */ 265 if (gethostname(host, sizeof(host)) < 0) 266 (void)strcpy(host, "???"); 267 now = time((time_t *)NULL); 268 nows = ctime(&now); 269 nows[16] = '\0'; 270 (void)printf("\r\n\007\007\007Message from %s@%s on %s at %s ...\r\n", 271 login, host, mytty, nows + 11); 272 273 while (fgets(line, sizeof(line), stdin) != NULL) 274 wr_fputs(line); 275 } 276 277 /* 278 * done - cleanup and exit 279 */ 280 void 281 done() 282 { 283 (void)printf("EOF\r\n"); 284 exit(0); 285 } 286 287 /* 288 * wr_fputs - like fputs(), but makes control characters visible and 289 * turns \n into \r\n 290 */ 291 void 292 wr_fputs(s) 293 register char *s; 294 { 295 register char c; 296 297 #define PUTC(c) if (putchar(c) == EOF) goto err; 298 299 for (; *s != '\0'; ++s) { 300 c = toascii(*s); 301 if (c == '\n') { 302 PUTC('\r'); 303 PUTC('\n'); 304 } else if (!isprint(c) && !isspace(c) && c != '\007') { 305 PUTC('^'); 306 PUTC(c^0x40); /* DEL to ?, others to alpha */ 307 } else 308 PUTC(c); 309 } 310 return; 311 312 err: err(1, NULL); 313 #undef PUTC 314 } 315
Indexes created Sun Sep 21 20:09:37 GMT 2025