write.c revision 11916
11590Srgrimes/* 21590Srgrimes * Copyright (c) 1989, 1993 31590Srgrimes * The Regents of the University of California. All rights reserved. 41590Srgrimes * 51590Srgrimes * This code is derived from software contributed to Berkeley by 61590Srgrimes * Jef Poskanzer and Craig Leres of the Lawrence Berkeley Laboratory. 71590Srgrimes * 81590Srgrimes * Redistribution and use in source and binary forms, with or without 91590Srgrimes * modification, are permitted provided that the following conditions 101590Srgrimes * are met: 111590Srgrimes * 1. Redistributions of source code must retain the above copyright 121590Srgrimes * notice, this list of conditions and the following disclaimer. 131590Srgrimes * 2. Redistributions in binary form must reproduce the above copyright 141590Srgrimes * notice, this list of conditions and the following disclaimer in the 151590Srgrimes * documentation and/or other materials provided with the distribution. 161590Srgrimes * 3. All advertising materials mentioning features or use of this software 171590Srgrimes * must display the following acknowledgement: 181590Srgrimes * This product includes software developed by the University of 191590Srgrimes * California, Berkeley and its contributors. 201590Srgrimes * 4. Neither the name of the University nor the names of its contributors 211590Srgrimes * may be used to endorse or promote products derived from this software 221590Srgrimes * without specific prior written permission. 231590Srgrimes * 241590Srgrimes * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 251590Srgrimes * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 261590Srgrimes * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 271590Srgrimes * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 281590Srgrimes * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 291590Srgrimes * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 301590Srgrimes * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 311590Srgrimes * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 321590Srgrimes * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 331590Srgrimes * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 341590Srgrimes * SUCH DAMAGE. 351590Srgrimes */ 361590Srgrimes 371590Srgrimes#ifndef lint 381590Srgrimesstatic char copyright[] = 391590Srgrimes"@(#) Copyright (c) 1989, 1993\n\ 401590Srgrimes The Regents of the University of California. All rights reserved.\n"; 411590Srgrimes#endif /* not lint */ 421590Srgrimes 431590Srgrimes#ifndef lint 441590Srgrimesstatic char sccsid[] = "@(#)write.c 8.1 (Berkeley) 6/6/93"; 451590Srgrimes#endif /* not lint */ 461590Srgrimes 471590Srgrimes#include <sys/param.h> 481590Srgrimes#include <sys/signal.h> 491590Srgrimes#include <sys/stat.h> 501590Srgrimes#include <sys/file.h> 511590Srgrimes#include <sys/time.h> 521590Srgrimes#include <utmp.h> 531590Srgrimes#include <ctype.h> 541590Srgrimes#include <pwd.h> 551590Srgrimes#include <stdio.h> 561590Srgrimes#include <string.h> 571590Srgrimes 581590Srgrimesextern int errno; 591590Srgrimes 601590Srgrimesmain(argc, argv) 611590Srgrimes int argc; 621590Srgrimes char **argv; 631590Srgrimes{ 641590Srgrimes register char *cp; 651590Srgrimes time_t atime; 661590Srgrimes uid_t myuid; 671590Srgrimes int msgsok, myttyfd; 681590Srgrimes char tty[MAXPATHLEN], *mytty, *ttyname(); 691590Srgrimes void done(); 701590Srgrimes 711590Srgrimes /* check that sender has write enabled */ 721590Srgrimes if (isatty(fileno(stdin))) 731590Srgrimes myttyfd = fileno(stdin); 741590Srgrimes else if (isatty(fileno(stdout))) 751590Srgrimes myttyfd = fileno(stdout); 761590Srgrimes else if (isatty(fileno(stderr))) 771590Srgrimes myttyfd = fileno(stderr); 781590Srgrimes else { 791590Srgrimes (void)fprintf(stderr, "write: can't find your tty\n"); 801590Srgrimes exit(1); 811590Srgrimes } 821590Srgrimes if (!(mytty = ttyname(myttyfd))) { 831590Srgrimes (void)fprintf(stderr, "write: can't find your tty's name\n"); 841590Srgrimes exit(1); 851590Srgrimes } 861590Srgrimes if (cp = rindex(mytty, '/')) 871590Srgrimes mytty = cp + 1; 881590Srgrimes if (term_chk(mytty, &msgsok, &atime, 1)) 891590Srgrimes exit(1); 901590Srgrimes if (!msgsok) { 911590Srgrimes (void)fprintf(stderr, 921590Srgrimes "write: you have write permission turned off.\n"); 931590Srgrimes exit(1); 941590Srgrimes } 951590Srgrimes 961590Srgrimes myuid = getuid(); 971590Srgrimes 981590Srgrimes /* check args */ 991590Srgrimes switch (argc) { 1001590Srgrimes case 2: 1011590Srgrimes search_utmp(argv[1], tty, mytty, myuid); 1021590Srgrimes do_write(tty, mytty, myuid); 1031590Srgrimes break; 1041590Srgrimes case 3: 1051590Srgrimes if (!strncmp(argv[2], "/dev/", 5)) 1061590Srgrimes argv[2] += 5; 1071590Srgrimes if (utmp_chk(argv[1], argv[2])) { 1081590Srgrimes (void)fprintf(stderr, 1091590Srgrimes "write: %s is not logged in on %s.\n", 1101590Srgrimes argv[1], argv[2]); 1111590Srgrimes exit(1); 1121590Srgrimes } 1131590Srgrimes if (term_chk(argv[2], &msgsok, &atime, 1)) 1141590Srgrimes exit(1); 1151590Srgrimes if (myuid && !msgsok) { 1161590Srgrimes (void)fprintf(stderr, 1171590Srgrimes "write: %s has messages disabled on %s\n", 1181590Srgrimes argv[1], argv[2]); 1191590Srgrimes exit(1); 1201590Srgrimes } 1211590Srgrimes do_write(argv[2], mytty, myuid); 1221590Srgrimes break; 1231590Srgrimes default: 1241590Srgrimes (void)fprintf(stderr, "usage: write user [tty]\n"); 1251590Srgrimes exit(1); 1261590Srgrimes } 1271590Srgrimes done(); 1281590Srgrimes /* NOTREACHED */ 1291590Srgrimes} 1301590Srgrimes 1311590Srgrimes/* 1321590Srgrimes * utmp_chk - checks that the given user is actually logged in on 1331590Srgrimes * the given tty 1341590Srgrimes */ 1351590Srgrimesutmp_chk(user, tty) 1361590Srgrimes char *user, *tty; 1371590Srgrimes{ 1381590Srgrimes struct utmp u; 1391590Srgrimes int ufd; 1401590Srgrimes 1411590Srgrimes if ((ufd = open(_PATH_UTMP, O_RDONLY)) < 0) 1421590Srgrimes return(0); /* ignore error, shouldn't happen anyway */ 1431590Srgrimes 1441590Srgrimes while (read(ufd, (char *) &u, sizeof(u)) == sizeof(u)) 1451590Srgrimes if (strncmp(user, u.ut_name, sizeof(u.ut_name)) == 0 && 1461590Srgrimes strncmp(tty, u.ut_line, sizeof(u.ut_line)) == 0) { 1471590Srgrimes (void)close(ufd); 1481590Srgrimes return(0); 1491590Srgrimes } 1501590Srgrimes 1511590Srgrimes (void)close(ufd); 1521590Srgrimes return(1); 1531590Srgrimes} 1541590Srgrimes 1551590Srgrimes/* 1561590Srgrimes * search_utmp - search utmp for the "best" terminal to write to 1571590Srgrimes * 1581590Srgrimes * Ignores terminals with messages disabled, and of the rest, returns 1591590Srgrimes * the one with the most recent access time. Returns as value the number 1601590Srgrimes * of the user's terminals with messages enabled, or -1 if the user is 1611590Srgrimes * not logged in at all. 1621590Srgrimes * 1631590Srgrimes * Special case for writing to yourself - ignore the terminal you're 1641590Srgrimes * writing from, unless that's the only terminal with messages enabled. 1651590Srgrimes */ 1661590Srgrimessearch_utmp(user, tty, mytty, myuid) 1671590Srgrimes char *user, *tty, *mytty; 1681590Srgrimes uid_t myuid; 1691590Srgrimes{ 1701590Srgrimes struct utmp u; 1711590Srgrimes time_t bestatime, atime; 1721590Srgrimes int ufd, nloggedttys, nttys, msgsok, user_is_me; 1731590Srgrimes char atty[UT_LINESIZE + 1]; 1741590Srgrimes 1751590Srgrimes if ((ufd = open(_PATH_UTMP, O_RDONLY)) < 0) { 1761590Srgrimes perror("utmp"); 1771590Srgrimes exit(1); 1781590Srgrimes } 1791590Srgrimes 1801590Srgrimes nloggedttys = nttys = 0; 1811590Srgrimes bestatime = 0; 1821590Srgrimes user_is_me = 0; 1831590Srgrimes while (read(ufd, (char *) &u, sizeof(u)) == sizeof(u)) 1841590Srgrimes if (strncmp(user, u.ut_name, sizeof(u.ut_name)) == 0) { 1851590Srgrimes ++nloggedttys; 1861590Srgrimes (void)strncpy(atty, u.ut_line, UT_LINESIZE); 1871590Srgrimes atty[UT_LINESIZE] = '\0'; 1881590Srgrimes if (term_chk(atty, &msgsok, &atime, 0)) 1891590Srgrimes continue; /* bad term? skip */ 1901590Srgrimes if (myuid && !msgsok) 1911590Srgrimes continue; /* skip ttys with msgs off */ 1921590Srgrimes if (strcmp(atty, mytty) == 0) { 1931590Srgrimes user_is_me = 1; 1941590Srgrimes continue; /* don't write to yourself */ 1951590Srgrimes } 1961590Srgrimes ++nttys; 1971590Srgrimes if (atime > bestatime) { 1981590Srgrimes bestatime = atime; 1991590Srgrimes (void)strcpy(tty, atty); 2001590Srgrimes } 2011590Srgrimes } 2021590Srgrimes 2031590Srgrimes (void)close(ufd); 2041590Srgrimes if (nloggedttys == 0) { 2051590Srgrimes (void)fprintf(stderr, "write: %s is not logged in\n", user); 2061590Srgrimes exit(1); 2071590Srgrimes } 2081590Srgrimes if (nttys == 0) { 2091590Srgrimes if (user_is_me) { /* ok, so write to yourself! */ 2101590Srgrimes (void)strcpy(tty, mytty); 2111590Srgrimes return; 2121590Srgrimes } 2131590Srgrimes (void)fprintf(stderr, 2141590Srgrimes "write: %s has messages disabled\n", user); 2151590Srgrimes exit(1); 2161590Srgrimes } else if (nttys > 1) { 2171590Srgrimes (void)fprintf(stderr, 2181590Srgrimes "write: %s is logged in more than once; writing to %s\n", 2191590Srgrimes user, tty); 2201590Srgrimes } 2211590Srgrimes} 2221590Srgrimes 2231590Srgrimes/* 2241590Srgrimes * term_chk - check that a terminal exists, and get the message bit 2251590Srgrimes * and the access time 2261590Srgrimes */ 2271590Srgrimesterm_chk(tty, msgsokP, atimeP, showerror) 2281590Srgrimes char *tty; 2291590Srgrimes int *msgsokP, showerror; 2301590Srgrimes time_t *atimeP; 2311590Srgrimes{ 2321590Srgrimes struct stat s; 2331590Srgrimes char path[MAXPATHLEN]; 2341590Srgrimes 2351590Srgrimes (void)sprintf(path, "/dev/%s", tty); 2361590Srgrimes if (stat(path, &s) < 0) { 2371590Srgrimes if (showerror) 2381590Srgrimes (void)fprintf(stderr, 2391590Srgrimes "write: %s: %s\n", path, strerror(errno)); 2401590Srgrimes return(1); 2411590Srgrimes } 2421590Srgrimes *msgsokP = (s.st_mode & (S_IWRITE >> 3)) != 0; /* group write bit */ 2431590Srgrimes *atimeP = s.st_atime; 2441590Srgrimes return(0); 2451590Srgrimes} 2461590Srgrimes 2471590Srgrimes/* 2481590Srgrimes * do_write - actually make the connection 2491590Srgrimes */ 2501590Srgrimesdo_write(tty, mytty, myuid) 2511590Srgrimes char *tty, *mytty; 2521590Srgrimes uid_t myuid; 2531590Srgrimes{ 2541590Srgrimes register char *login, *nows; 2551590Srgrimes register struct passwd *pwd; 2561590Srgrimes time_t now, time(); 2571590Srgrimes char *getlogin(), path[MAXPATHLEN], host[MAXHOSTNAMELEN], line[512]; 2581590Srgrimes void done(); 2591590Srgrimes 2601590Srgrimes /* Determine our login name before the we reopen() stdout */ 2611590Srgrimes if ((login = getlogin()) == NULL) 2621590Srgrimes if (pwd = getpwuid(myuid)) 2631590Srgrimes login = pwd->pw_name; 2641590Srgrimes else 2651590Srgrimes login = "???"; 2661590Srgrimes 2671590Srgrimes (void)sprintf(path, "/dev/%s", tty); 2681590Srgrimes if ((freopen(path, "w", stdout)) == NULL) { 2691590Srgrimes (void)fprintf(stderr, "write: %s: %s\n", path, strerror(errno)); 2701590Srgrimes exit(1); 2711590Srgrimes } 2721590Srgrimes 2731590Srgrimes (void)signal(SIGINT, done); 2741590Srgrimes (void)signal(SIGHUP, done); 2751590Srgrimes 2761590Srgrimes /* print greeting */ 2771590Srgrimes if (gethostname(host, sizeof(host)) < 0) 2781590Srgrimes (void)strcpy(host, "???"); 2791590Srgrimes now = time((time_t *)NULL); 2801590Srgrimes nows = ctime(&now); 2811590Srgrimes nows[16] = '\0'; 2821590Srgrimes (void)printf("\r\n\007\007\007Message from %s@%s on %s at %s ...\r\n", 2831590Srgrimes login, host, mytty, nows + 11); 2841590Srgrimes 2851590Srgrimes while (fgets(line, sizeof(line), stdin) != NULL) 2861590Srgrimes wr_fputs(line); 2871590Srgrimes} 2881590Srgrimes 2891590Srgrimes/* 2901590Srgrimes * done - cleanup and exit 2911590Srgrimes */ 2921590Srgrimesvoid 2931590Srgrimesdone() 2941590Srgrimes{ 2951590Srgrimes (void)printf("EOF\r\n"); 2961590Srgrimes exit(0); 2971590Srgrimes} 2981590Srgrimes 2991590Srgrimes/* 3001590Srgrimes * wr_fputs - like fputs(), but makes control characters visible and 3011590Srgrimes * turns \n into \r\n 3021590Srgrimes */ 3031590Srgrimeswr_fputs(s) 3041590Srgrimes register char *s; 3051590Srgrimes{ 3061590Srgrimes 3071590Srgrimes#define PUTC(c) if (putchar(c) == EOF) goto err; 3081590Srgrimes 3091590Srgrimes for (; *s != '\0'; ++s) { 31011916Sache if (*s == '\n') { 3111590Srgrimes PUTC('\r'); 3121590Srgrimes PUTC('\n'); 31311916Sache } else if (!isprint(*s) && !isspace(*s) && *s != '\007') { 3141590Srgrimes PUTC('^'); 31511916Sache PUTC((*s^0x40)&~0x80); /* DEL to ?, others to alpha */ 3161590Srgrimes } else 31711916Sache PUTC(*s); 3181590Srgrimes } 3191590Srgrimes return; 3201590Srgrimes 3211590Srgrimeserr: (void)fprintf(stderr, "write: %s\n", strerror(errno)); 3221590Srgrimes exit(1); 3231590Srgrimes#undef PUTC 3241590Srgrimes} 325