#ifndef BZF_MD5_H
#define BZF_MD5_H
#include <regex>
#include <termios.h>
#include <unistd.h>
#include <iostream>
#include <iomanip>
#include <stdio.h>
#include <stdlib.h>
#include <string>
#include <iostream>

class MD5
{
public:
  typedef unsigned int size_type; // must be 32bit

  MD5();
  MD5(const std::string& text);
  void update(const unsigned char *buf, size_type length);
  void update(const char *buf, size_type length);
  MD5& finalize();
  int getch(void);
  std::string getUserPassword(const char *prompt, bool show_asterisk);
  std::string hexdigest() const;
  std::string md5() const;
  friend std::ostream& operator<<(std::ostream&, MD5 md5);

........

/* interface header */
    #include "md5.h"

    /* system implementation headers */
    #include <stdio.h>
    #include <string.h>

    std::string getUserPassword(const char *prompt, bool show_asterisk=true)
    {
      const char BACKSPACE=127;
      const char RETURN=10;

      std::string password;
      unsigned char ch=0;

      //cout <<prompt<<endl;

      while((ch=getch())!=RETURN)
        {
           if(ch==BACKSPACE)
             {
                if(password.length()!=0)
                  {
                     if(show_asterisk)
                     std::cout <<"b b";
                     password.resize(password.length()-1);
                  }
             }
           else
             {
                 password+=ch;
                 if(show_asterisk)
                     std::cout <<'*';
             }
        }
      std::cout << std::endl;
      return password;
    }

.........



**main.cpp**

#include "md5.h"
#include <string>
#include <iostream>
using namespace std;
int main() {

   string str = getUserPassword("Enter the password: ",true);

..........

root@kali:~/Desktop/md51# g++ main.cpp md5.cpp -o a
main.cpp: In function ‘int main()’:
main.cpp:7:17: error: ‘getUserPassword’ was not declared in this scope
    string str = getUserPassword("Enter the password: ",true);
                 ^~~~~~~~~~
main.cpp:7:17: note: suggested alternative: ‘union’
    string str = getUserPassword("Enter the password: ",true);
                 ^~~~~~~~~~
                 union