UNIX 7th Ed. - /usr/src/cmd/write.c

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

Defined functions

Defined variables