#include <unistd.h>
     #include <sys/types.h>
     #include <unistd.h>
    #define EOF -1
    #define STD_IN 0
    #define STD_OUT 1

    int main(int argc, char *argv[]){

    int fd[2];
     int c;
    pipe(&fd[0]);
    if (fork()!=0){
	close(fd[0]) ;
	close(STD_IN);
	//close(STD_OUT);
	dup(fd[1]);
	close(fd[1]);
	execlp("/bin/cat","cat","hola.txt", NULL);
    } else {
	close(fd[1]);
	close(STD_IN);
	dup(fd[0]);

	while((c=getchar())!= EOF){
			if(c=='A')
				putchar('X');
			else
				putchar(c);
		}
	execlp("sort","sort",NULL);
    }
    }