/* 2001 March 27

   ^D flushes the input stream [read() returns].
   There is no EOF character.  EOF is indicated by a read that returns
   no characters.
*/

#include <stdio.h>

main() {
   int c;
   FILE *fp;

   printf("Program to illustrate ^D and EOF handling by the terminal driver.\n");
   printf("There is no EOF character in UNIX.\n");
   printf("^D merely flushes the input stream - causes read to return.\n");
   printf("An Enter/Carriage-return, appends newline to the current line\n");
   printf(" and then causes the read to return.\n");
   printf("A read that returns no characters is interpreted as an EOF.\n\n");
   printf("It follows that you can read through EOF's and that an\n");
   printf(" EOF is obtained by ^D at beginning of line, or ^D^D in midline.\n");
   printf(" (the first ^D flushes the line, the next flushes with no characters)\n");
   printf("Try it:\n");
   
   if(0 != system("PS1= xterm -C &"))
      fprintf(stderr,"Warning: cannot open terminal for /dev/console\n");
   
   fp = fopen("/dev/console","w");
   if (fp == NULL) {
      fprintf(stderr,"cannot open /dev/console\n");
      exit(1);
   }
   for(;;) switch(c = getchar()) {
	 case '\n':
	    fprintf(fp,"Saw: newline (hexdecimal code: %02x)\n",c,c);
	    break;
	 case EOF:
	    fprintf(fp,"Saw EOF: read of zero bytes\n");
	    break;
	 default:
	    fprintf(fp,"Saw: %c (hexdecimal-code: %02x)\n",c,c);
   }
}