enviar contraseña y escribirla automaticamente en el prompt de linux

#include<stdio.h>
#include<string.h>
#include<unistd.h>
#include<fcntl.h>
#include<sys/types.h>
#include<sys/stat.h>

int main(){
  int fd;

  char * myfifo = "/tmp/myfifo";

  mkfifo(myfifo, 0666);

  char arr1[80], arr2[80];
  while(1){
    fd = open(myfifo, O_WRONLY);
    fgets(arr2, 80, stdin);
    write(fd, arr2, strlen(arr2)+1);
    close(fd);

    fd = open(myfifo, O_RDONLY);
    read(fd, arr1, sizeof(arr1));
    printf("User2: %s\n", arr1);
    close(fd);
  }

  return 0;
}