1 static char *sccsid = "@(#)write.c 4.7 03/01/83"; 2 /* 3 * write to another user 4 */ 5 6 #include <stdio.h> 7 #include <sys/types.h> 8 #include <sys/stat.h> 9 #include <signal.h> 10 #include <utmp.h> 11 #include <time.h> 12 13 #define NMAX sizeof(ubuf.ut_name) 14 #define LMAX sizeof(ubuf.ut_line) 15 16 char *strcat(); 17 char *strcpy(); 18 struct utmp ubuf; 19 int signum[] = {SIGHUP, SIGINT, SIGQUIT, 0}; 20 char me[10] = "???"; 21 char *him; 22 char *mytty; 23 char histty[32]; 24 char *histtya; 25 char *ttyname(); 26 char *rindex(); 27 int logcnt; 28 int eof(); 29 int timout(); 30 FILE *tf; 31 char *getenv(); 32 33 main(argc, argv) 34 int argc; 35 char *argv[]; 36 { 37 struct stat stbuf; 38 register i; 39 register FILE *uf; 40 int c1, c2; 41 long clock = time(0); 42 struct tm *localtime(); 43 struct tm *localclock = localtime( &clock ); 44 45 if (argc < 2) { 46 printf("usage: write user [ttyname]\n"); 47 exit(1); 48 } 49 him = argv[1]; 50 if (argc > 2) 51 histtya = argv[2]; 52 if ((uf = fopen("/etc/utmp", "r")) == NULL) { 53 printf("cannot open /etc/utmp\n"); 54 goto cont; 55 } 56 mytty = ttyname(2); 57 if (mytty == NULL) { 58 printf("Can't find your tty\n"); 59 exit(1); 60 } 61 if (stat(mytty, &stbuf) < 0) { 62 printf("Can't stat your tty\n"); 63 exit(1); 64 } 65 if ((stbuf.st_mode&02) == 0) { 66 printf("You have write permission turned off.\n"); 67 exit(1); 68 } 69 mytty = rindex(mytty, '/') + 1; 70 if (histtya) { 71 strcpy(histty, "/dev/"); 72 strcat(histty, histtya); 73 } 74 while (fread((char *)&ubuf, sizeof(ubuf), 1, uf) == 1) { 75 if (ubuf.ut_name[0] == '\0') 76 continue; 77 if (strcmp(ubuf.ut_line, mytty)==0) { 78 for (i=0; i<NMAX; i++) { 79 c1 = ubuf.ut_name[i]; 80 if (c1 == ' ') 81 c1 = 0; 82 me[i] = c1; 83 if (c1 == 0) 84 break; 85 } 86 } 87 if (him[0] != '-' || him[1] != 0) 88 for (i=0; i<NMAX; i++) { 89 c1 = him[i]; 90 c2 = ubuf.ut_name[i]; 91 if (c1 == 0) 92 if (c2 == 0 || c2 == ' ') 93 break; 94 if (c1 != c2) 95 goto nomat; 96 } 97 logcnt++; 98 if (histty[0]==0) { 99 strcpy(histty, "/dev/"); 100 strcat(histty, ubuf.ut_line); 101 } 102 nomat: 103 ; 104 } 105 cont: 106 if (logcnt==0 && histty[0]=='\0') { 107 printf("%s not logged in.\n", him); 108 exit(1); 109 } 110 fclose(uf); 111 if (histtya==0 && logcnt > 1) { 112 printf("%s logged more than once\nwriting to %s\n", him, histty+5); 113 } 114 if (histty[0] == 0) { 115 printf(him); 116 if (logcnt) 117 printf(" not on that tty\n"); else 118 printf(" not logged in\n"); 119 exit(1); 120 } 121 if (access(histty, 0) < 0) { 122 printf("No such tty\n"); 123 exit(1); 124 } 125 signal(SIGALRM, timout); 126 alarm(5); 127 if ((tf = fopen(histty, "w")) == NULL) 128 goto perm; 129 alarm(0); 130 if (fstat(fileno(tf), &stbuf) < 0) 131 goto perm; 132 if ((stbuf.st_mode&02) == 0) 133 goto perm; 134 sigs(eof); 135 { char hostname[32]; 136 gethostname(hostname, sizeof (hostname)); 137 fprintf(tf, "\r\nMessage from "); 138 fprintf(tf, "%s!%s on %s at %d:%02d ...\r\n\007\007\007", 139 hostname, me, mytty, localclock->tm_hour, localclock->tm_min); 140 } 141 fflush(tf); 142 for (;;) { 143 char buf[128]; 144 i = read(0, buf, 128); 145 if (i <= 0) 146 eof(); 147 if (buf[0] == '!') { 148 buf[i] = 0; 149 ex(buf); 150 continue; 151 } 152 if (write(fileno(tf), buf, i) != i) { 153 printf("\n\007Write failed (%s logged out?)\n", him); 154 exit(1); 155 } 156 if (buf[i-1] == '\n') 157 write(fileno(tf), "\r", 1); 158 } 159 perm: 160 printf("Permission denied\n"); 161 exit(1); 162 } 163 164 timout() 165 { 166 167 printf("Timeout opening their tty\n"); 168 exit(1); 169 } 170 171 eof() 172 { 173 174 fprintf(tf, "EOF\r\n"); 175 exit(0); 176 } 177 178 ex(bp) 179 char *bp; 180 { 181 register i; 182 183 sigs(SIG_IGN); 184 i = fork(); 185 if (i < 0) { 186 printf("Try again\n"); 187 goto out; 188 } 189 if (i == 0) { 190 sigs((int (*)())0); 191 execl(getenv("SHELL") ? 192 getenv("SHELL") : "/bin/sh", "sh", "-c", bp+1, 0); 193 exit(0); 194 } 195 while (wait((int *)NULL) != i) 196 ; 197 printf("!\n"); 198 out: 199 sigs(eof); 200 } 201 202 sigs(sig) 203 int (*sig)(); 204 { 205 register i; 206 207 for (i=0; signum[i]; i++) 208 signal(signum[i], sig); 209 } 210