1: #ifndef lint
   2: static char *sccsid = "@(#)write.c	4.13 3/13/86";
   3: #endif
   4: /*
   5:  * write to another user
   6:  */
   7: 
   8: #include <stdio.h>
   9: #include <ctype.h>
  10: #include <sys/types.h>
  11: #include <sys/stat.h>
  12: #include <signal.h>
  13: #include <utmp.h>
  14: #include <sys/time.h>
  15: 
  16: #define NMAX    sizeof(ubuf.ut_name)
  17: #define LMAX    sizeof(ubuf.ut_line)
  18: 
  19: char    *strcat();
  20: char    *strcpy();
  21: struct  utmp ubuf;
  22: int signum[] = {SIGHUP, SIGINT, SIGQUIT, 0};
  23: char    me[NMAX + 1]    = "???";
  24: char    *him;
  25: char    *mytty;
  26: char    histty[32];
  27: char    ttybuf[32];
  28: char    *histtya;
  29: char    *ttyname();
  30: char    *rindex();
  31: int logcnt;
  32: int eof();
  33: int timout();
  34: FILE    *tf;
  35: char    *getenv();
  36: 
  37: main(argc, argv)
  38:     int argc;
  39:     char *argv[];
  40: {
  41:     struct stat stbuf;
  42:     register i;
  43:     register FILE *uf;
  44:     int c1, c2;
  45:     long clock = time(0);
  46:     int suser = getuid() == 0;
  47:     int nomesg = 0;
  48:     struct tm *localtime();
  49:     struct tm *localclock = localtime( &clock );
  50: 
  51:     if (argc < 2) {
  52:         fprintf(stderr, "Usage: write user [ttyname]\n");
  53:         exit(1);
  54:     }
  55:     him = argv[1];
  56:     if (argc > 2)
  57:         histtya = argv[2];
  58:     if ((uf = fopen("/etc/utmp", "r")) == NULL) {
  59:         perror("write: Can't open /etc/utmp");
  60:         if (histtya == 0)
  61:             exit(10);
  62:         goto cont;
  63:     }
  64:     mytty = ttyname(2);
  65:     if (mytty == NULL) {
  66:         fprintf(stderr, "write: Can't find your tty\n");
  67:         exit(1);
  68:     }
  69:     if (stat(mytty, &stbuf) < 0) {
  70:         perror("write: Can't stat your tty");
  71:         exit(1);
  72:     }
  73:     if ((stbuf.st_mode&020) == 0) {
  74:         fprintf(stderr,
  75:             "write: You have write permission turned off\n");
  76:         if (!suser)
  77:             exit(1);
  78:     }
  79:     mytty = rindex(mytty, '/') + 1;
  80:     if (histtya) {
  81:         strcpy(histty, "/dev/");
  82:         strcat(histty, histtya);
  83:     }
  84:     while (fread((char *)&ubuf, sizeof(ubuf), 1, uf) == 1) {
  85:         if (ubuf.ut_name[0] == '\0')
  86:             continue;
  87:         if (strcmp(ubuf.ut_line, mytty)==0) {
  88:             for (i=0; i<NMAX; i++) {
  89:                 c1 = ubuf.ut_name[i];
  90:                 if (c1 == ' ')
  91:                     c1 = 0;
  92:                 me[i] = c1;
  93:                 if (c1 == 0)
  94:                     break;
  95:             }
  96:         }
  97:         if (him[0] == '-' && him[1] == 0)
  98:             goto nomat;
  99:         for (i=0; i<NMAX; i++) {
 100:             c1 = him[i];
 101:             c2 = ubuf.ut_name[i];
 102:             if (c1 == 0)
 103:                 if (c2 == 0 || c2 == ' ')
 104:                     break;
 105:             if (c1 != c2)
 106:                 goto nomat;
 107:         }
 108:         if (histtya && strncmp(histtya, ubuf.ut_line,
 109:             sizeof(ubuf.ut_line)))
 110:             continue;
 111:         logcnt++;
 112:         if (histty[0]==0 || nomesg && histtya == 0) {
 113:             strcpy(ttybuf, "/dev/");
 114:             strcat(ttybuf, ubuf.ut_line);
 115:             if (histty[0]==0)
 116:                 strcpy(histty, ttybuf);
 117:             if (access(ttybuf, 0) < 0 || stat(ttybuf, &stbuf) < 0 ||
 118:                 (stbuf.st_mode&020) == 0)
 119:                 nomesg++;
 120:             else {
 121:                 strcpy(histty, ttybuf);
 122:                 nomesg = 0;
 123:             }
 124:         }
 125:     nomat:
 126:         ;
 127:     }
 128:     fclose(uf);
 129:     if (logcnt==0) {
 130:         fprintf(stderr, "write: %s not logged in%s\n", him,
 131:             histtya ? " on that tty" : "");
 132:         exit(1);
 133:     }
 134:     if (histtya==0 && logcnt > 1) {
 135:         fprintf(stderr,
 136:         "write: %s logged in more than once ... writing to %s\n",
 137:             him, histty+5);
 138:     }
 139: cont:
 140:     if (access(histty, 0) < 0) {
 141:         fprintf(stderr, "write: No such tty\n");
 142:         exit(1);
 143:     }
 144:     signal(SIGALRM, timout);
 145:     alarm(5);
 146:     if ((tf = fopen(histty, "w")) == NULL) {
 147:         fprintf(stderr, "write: Permission denied\n");
 148:         exit(1);
 149:     }
 150:     alarm(0);
 151:     sigs(eof);
 152:     { char hostname[32];
 153:       gethostname(hostname, sizeof (hostname));
 154:       fprintf(tf,
 155:           "\r\nMessage from %s@%s on %s at %d:%02d ...\r\n\007\007\007",
 156:           me, hostname, mytty, localclock->tm_hour, localclock->tm_min);
 157:     fflush(tf);
 158:     }
 159:     for (;;) {
 160:         char buf[BUFSIZ];
 161:         register char *bp;
 162:         i = read(0, buf, sizeof buf);
 163:         if (i <= 0)
 164:             eof();
 165:         if (buf[0] == '!') {
 166:             buf[i] = 0;
 167:             ex(buf);
 168:             continue;
 169:         }
 170:         for (bp = buf; --i >= 0; bp++) {
 171:             if (*bp == '\n')
 172:                 putc('\r', tf);
 173: 
 174:             if (!isascii(*bp)) {
 175:                 putc('M', tf);
 176:                 putc('-', tf);
 177:                 *bp = toascii(*bp);
 178:             }
 179: 
 180:             if (isprint(*bp) ||
 181:                 *bp == ' ' || *bp == '\t' || *bp == '\n') {
 182:                 putc(*bp, tf);
 183:             } else {
 184:                 putc('^', tf);
 185:                 putc(*bp ^ 0100, tf);
 186:             }
 187: 
 188:             if (*bp == '\n')
 189:                 fflush(tf);
 190: 
 191:             if (ferror(tf) || feof(tf)) {
 192:                 printf("\n\007Write failed (%s logged out?)\n",
 193:                     him);
 194:                 exit(1);
 195:             }
 196:         }
 197:     }
 198: }
 199: 
 200: timout()
 201: {
 202: 
 203:     fprintf(stderr, "write: Timeout opening their tty\n");
 204:     exit(1);
 205: }
 206: 
 207: eof()
 208: {
 209: 
 210:     fprintf(tf, "EOF\r\n");
 211:     exit(0);
 212: }
 213: 
 214: ex(bp)
 215:     char *bp;
 216: {
 217:     register i;
 218: 
 219:     sigs(SIG_IGN);
 220:     i = fork();
 221:     if (i < 0) {
 222:         printf("Try again\n");
 223:         goto out;
 224:     }
 225:     if (i == 0) {
 226:         fclose(tf);     /* Close his terminal */
 227:         setgid(getgid());   /* Give up effective group privs */
 228:         sigs((int (*)())0);
 229:         execl(getenv("SHELL") ?
 230:             getenv("SHELL") : "/bin/sh", "sh", "-c", bp+1, 0);
 231:         exit(0);
 232:     }
 233:     while (wait((int *)NULL) != i)
 234:         ;
 235:     printf("!\n");
 236: out:
 237:     sigs(eof);
 238: }
 239: 
 240: sigs(sig)
 241:     int (*sig)();
 242: {
 243:     register i;
 244: 
 245:     for (i=0; signum[i]; i++)
 246:         signal(signum[i], sig);
 247: }

Defined functions

eof defined in line 207; used 4 times
ex defined in line 214; used 1 times
main defined in line 37; never used
sigs defined in line 240; used 4 times
timout defined in line 200; used 2 times

Defined variables

him defined in line 24; used 7 times
histty defined in line 26; used 9 times
histtya defined in line 28; used 9 times
logcnt defined in line 31; used 3 times
me defined in line 23; used 2 times
mytty defined in line 25; used 7 times
sccsid defined in line 2; never used
signum defined in line 22; used 2 times
ttybuf defined in line 27; used 6 times
ubuf defined in line 21; used 11 times

Defined macros

LMAX defined in line 17; never used
NMAX defined in line 16; used 3 times
Last modified: 1986-03-14
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