// File: termdemo.c
// Demo of select, with terminal functions, too.

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/msg.h>
#include <sys/termios.h>

#define READ_END	0
#define WRITE_END	1

void main(argc, argv)
int argc ;
char *argv[] ;
{
 int PipeDes[2] ;		// pipe
 int Child ;			// there's going to be a fork
 int i;
 int OwnPid = getpid() ;   // hold own pid
 fd_set fdvar ;      	// The file descriptor set
 int ReadEnd, UserRead ;   // Pipe ends
 FILE *fp ;      	// Open a file
 int done = 0, RetVal ;
 char buf[20],command ;
 struct termios term, termsave ;

 /*** attach fp to stdin ***/
 fp = fopen(ctermid(NULL), "r+") ;
 setbuf(fp, NULL) ;      // No buffering of input
 UserRead = fileno(fp) ;   // UserRead will be the terminal's fd

 if(pipe(PipeDes)<0)
 {
    perror("Pipe error ") ;
    exit(1) ;
 }

 if((Child=fork())==0)   /*** if child process ***/
 {
    close(PipeDes[READ_END]) ;

    for(i=65; i<74; i++)  // 'A' through 'J'
    {
       write(PipeDes[WRITE_END], &i, sizeof(i)) ;
       sleep(1) ;
    }
    i = -1 ;
    write(PipeDes[WRITE_END], &i, sizeof(int)) ; 
 }  // child
 else
    if(Child>0)   /*** if parent process ***/
    {
       close(PipeDes[WRITE_END]) ;
       ReadEnd = PipeDes[READ_END] ;
       
       while(!done)
       {
          FD_ZERO(&fdvar) ;
          FD_SET(ReadEnd, &fdvar) ;
          FD_SET(UserRead, &fdvar) ;

         // Get parameters of terminal; place into itermios struct termsave
          tcgetattr(UserRead, &termsave) ;
         // want to save initial condition, so will manipulate term
          term = termsave ;
         // echo characters. Allow any size input. See termios man page
         // term.c_lflag &= ~(ECHO | ECHOE | ECHOK | ECHONL | ICANON) ;
          term.c_lflag &= (ECHO) ;
         // Record changes to UserRead made by changing the c_lflag
          tcsetattr(UserRead, TCSANOW, &term) ;
         // Set up the select to listen; only using read fds (others are null)
          select(32, &fdvar, (fd_set *)0, (fd_set *)0, NULL ) ;
         // Restore UserRead to default after output
          tcsetattr(UserRead, /* TCSAFLUSH */ TCSADRAIN, &termsave);
          if(FD_ISSET(ReadEnd, &fdvar))
          {
             read(ReadEnd, &i, sizeof(int)) ;
             if(i==-1)
                done++ ;
             else
                write(1, &i,sizeof(i));

          }
          
          if(FD_ISSET(UserRead, &fdvar))
          {   
             if((RetVal=read(UserRead, buf, sizeof(buf)))>1) 
             {
                fprintf(stderr,"Stdin: %d chars -- %s\n",RetVal,buf);
                write(1, buf, RetVal) ;
                sleep(1);
             }
          }
          
          printf("\n") ;
       }
    }  // Parent
    else
    {
       perror("Fork error ") ;
       exit(1) ;
    }
}