echo asdf | xterm | cat

#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <fcntl.h>

#include <stdio.h>
#include <stdlib.h>

int main(void)
{
	char *cmd[]={"cat", NULL};
	pid_t pid;
	int pipei[2], pipeo[2], status;
	char buf[512];
	ssize_t bytes;
	int total=0;

	// Create pipes
	pipe(pipei);	pipe(pipeo);

	pid=fork();

	if(pid < 0)
	{
		perror("Couldn't fork");
		return(1);
	}
	else if(pid == 0)
	{	// Child code
		// Child reads from output pipe
		dup2(pipeo[STDIN_FILENO], STDIN_FILENO);
		// Child writes to input pipe
		dup2(pipei[STDOUT_FILENO], STDOUT_FILENO);
		close(pipeo[STDOUT_FILENO]);
		close(pipei[STDIN_FILENO]);

		execvp(cmd[0], cmd);
		perror("Couldn't exec");
		exit(1);
	}

	// Parent code
	// Close all ends of pipes we aren't using anymore, or else
	// they'll hold it open later
	close(pipeo[STDIN_FILENO]);	close(pipei[STDOUT_FILENO]);

	write(pipeo[STDOUT_FILENO], "asdf", 4);

	// Read until EOF
	while(1)
	{
		bytes=read(pipei[STDIN_FILENO], buf, 512);
		if(bytes < 0)
		{
			fprintf(stderr, "Pipe not ready\n");
			continue;
		}
		else if(bytes == 0)	// End of file
		{
			fprintf(stderr, "Pipe closed\n");
			break;
		}
		else
		{
			fprintf(stderr, "Read %d bytes: '", (int)bytes);
			write(STDOUT_FILENO, buf, bytes);
			fprintf(stderr, "'\n");

			bytes=read(pipei[STDIN_FILENO], buf, 512);
		}
	}

	// Close the last pipes
	close(pipei[STDIN_FILENO]);
	close(pipeo[STDOUT_FILENO]);

	// Wait for the child so it doesn't haunt us as a zombie
	pid=wait(&status);

	fprintf(stderr, "Child exited with status %d\n", WEXITSTATUS(status));
}

xterm -S ab12

// pseudocode that creates its own xterm

main()
{
  create_socketpair();
  create_child();

  child_code
  {
      create_xterm();
  }

  parent_code
  {
    char *output="Hello, please type something here:";
    char input[512];

    // write output string
    while(!all_written)
      keep_writing_to_socket;

    // keep reading until we get EOF or an enter character
    while(!all_read)
      keep_reading_from_socket;

    output="you typed: ";
    while(!all_written)
      keep_writing_to_socket;

    output=input;
    while(!all_written)
      keep_writing_to_socket;
    output="'\n";

    while(!all_written)
      keep_writing_to_socket;

    close(socket);
    wait();
  }
}

//WORKING code that runs INSIDE  an xterm
#include <stdio.h>
int main(void)
{
    char buf[512];
    fprintf(stderr, "Hello, please type something here:");
    fgets(buf, 512, stdin);
    fprintf(stderr, "You typed: %s\n", buf);
}