C ++ reads the configuration file

//Config.h  #pragma once    #include <string>  #include <map>  #include <iostream>  #include <fstream>  #include <sstream>      /* * \brief Generic configuration Class * */  class Config {      // Data  protected:      std::string m_Delimiter;  //!< separator between key and value      std::string m_Comment;    //!< separator between value and comments      std::map<std::string,std::string> m_Contents;  //!< extracted keys and values        typedef std::map<std::string,std::string>::iterator mapi;      typedef std::map<std::string,std::string>::const_iterator mapci;      // Methods  public:        Config( std::string filename,std::string delimiter = "=",std::string comment = "#" );      Config();      template<class T> T Read( const std::string& in_key ) const;  //!<Search for key and read value or optional default value, call as read<T>      template<class T> T Read( const std::string& in_key, const T& in_value ) const;      template<class T> bool ReadInto( T& out_var, const std::string& in_key ) const;      template<class T>      bool ReadInto( T& out_var, const std::string& in_key, const T& in_value ) const;      bool FileExist(std::string filename);      void ReadFile(std::string filename,std::string delimiter = "=",std::string comment = "#" );        // Check whether key exists in configuration      bool KeyExists( const std::string& in_key ) const;        // Modify keys and values      template<class T> void Add( const std::string& in_key, const T& in_value );      void Remove( const std::string& in_key );        // Check or change configuration syntax      std::string GetDelimiter() const { return m_Delimiter; }      std::string GetComment() const { return m_Comment; }      std::string SetDelimiter( const std::string& in_s )      { std::string old = m_Delimiter;  m_Delimiter = in_s;  return old; }        std::string SetComment( const std::string& in_s )      { std::string old = m_Comment;  m_Comment =  in_s;  return old; }        // Write or read configuration      friend std::ostream& operator<<( std::ostream& os, const Config& cf );      friend std::istream& operator>>( std::istream& is, Config& cf );    protected:      template<class T> static std::string T_as_string( const T& t );      template<class T> static T string_as_T( const std::string& s );      static void Trim( std::string& inout_s );          // Exception types  public:      struct File_not_found {          std::string filename;          File_not_found( const std::string& filename_ = std::string() )              : filename(filename_) {} };          struct Key_not_found {  // thrown only by T read(key) variant of read()              std::string key;              Key_not_found( const std::string& key_ = std::string() )                  : key(key_) {} };  };      /* static */  template<class T>  std::string Config::T_as_string( const T& t )  {      // Convert from a T to a string      // Type T must support << operator      std::ostringstream ost;      ost << t;      return ost.str();  }      /* static */  template<class T>  T Config::string_as_T( const std::string& s )  {      // Convert from a string to a T      // Type T must support >> operator      T t;      std::istringstream ist(s);      ist >> t;      return t;  }      /* static */  template<>  inline std::string Config::string_as_T<std::string>( const std::string& s )  {      // Convert from a string to a string      // In other words, do nothing      return s;  }      /* static */  template<>  inline bool Config::string_as_T<bool>( const std::string& s )  {      // Convert from a string to a bool      // Interpret "false", "F", "no", "n", "0" as false      // Interpret "true", "T", "yes", "y", "1", "-1", or anything else as true      bool b = true;      std::string sup = s;      for( std::string::iterator p = sup.begin(); p != sup.end(); ++p )          *p = toupper(*p);  // make string all caps      if( sup==std::string("FALSE") || sup==std::string("F") ||          sup==std::string("NO") || sup==std::string("N") ||          sup==std::string("0") || sup==std::string("NONE") )          b = false;      return b;  }      template<class T>  T Config::Read( const std::string& key ) const  {      // Read the value corresponding to key      mapci p = m_Contents.find(key);      if( p == m_Contents.end() ) throw Key_not_found(key);      return string_as_T<T>( p->second );  }      template<class T>  T Config::Read( const std::string& key, const T& value ) const  {      // Return the value corresponding to key or given default value      // if key is not found      mapci p = m_Contents.find(key);      if( p == m_Contents.end() ) return value;      return string_as_T<T>( p->second );  }      template<class T>  bool Config::ReadInto( T& var, const std::string& key ) const  {      // Get the value corresponding to key and store in var      // Return true if key is found      // Otherwise leave var untouched      mapci p = m_Contents.find(key);      bool found = ( p != m_Contents.end() );      if( found ) var = string_as_T<T>( p->second );      return found;  }      template<class T>  bool Config::ReadInto( T& var, const std::string& key, const T& value ) const  {      // Get the value corresponding to key and store in var      // Return true if key is found      // Otherwise set var to given default      mapci p = m_Contents.find(key);      bool found = ( p != m_Contents.end() );      if( found )          var = string_as_T<T>( p->second );      else          var = value;      return found;  }      template<class T>  void Config::Add( const std::string& in_key, const T& value )  {      // Add a key with given value      std::string v = T_as_string( value );      std::string key=in_key;      Trim(key);      Trim(v);      m_Contents[key] = v;      return;  }  

// Config.cpp    #include "Config.h"    using namespace std;      Config::Config( string filename, string delimiter,                 string comment )                 : m_Delimiter(delimiter), m_Comment(comment)  {      // Construct a Config, getting keys and values from given file        std::ifstream in( filename.c_str() );        if( !in ) throw File_not_found( filename );         in >> (*this);  }      Config::Config()  : m_Delimiter( string(1,'=') ), m_Comment( string(1,'#') )  {      // Construct a Config without a file; empty  }        bool Config::KeyExists( const string& key ) const  {      // Indicate whether key is found      mapci p = m_Contents.find( key );      return ( p != m_Contents.end() );  }      /* static */  void Config::Trim( string& inout_s )  {      // Remove leading and trailing whitespace      static const char whitespace[] = " \n\t\v\r\f";      inout_s.erase( 0, inout_s.find_first_not_of(whitespace) );      inout_s.erase( inout_s.find_last_not_of(whitespace) + 1U );  }      std::ostream& operator<<( std::ostream& os, const Config& cf )  {      // Save a Config to os      for( Config::mapci p = cf.m_Contents.begin();          p != cf.m_Contents.end();          ++p )      {          os << p->first << " " << cf.m_Delimiter << " ";          os << p->second << std::endl;      }      return os;  }    void Config::Remove( const string& key )  {      // Remove key and its value      m_Contents.erase( m_Contents.find( key ) );      return;  }    std::istream& operator>>( std::istream& is, Config& cf )  {      // Load a Config from is      // Read in keys and values, keeping internal whitespace      typedef string::size_type pos;      const string& delim  = cf.m_Delimiter;  // separator      const string& comm   = cf.m_Comment;    // comment      const pos skip = delim.length();        // length of separator        string nextline = "";  // might need to read ahead to see where value ends        while( is || nextline.length() > 0 )      {          // Read an entire line at a time          string line;          if( nextline.length() > 0 )          {              line = nextline;  // we read ahead; use it now              nextline = "";          }          else          {              std::getline( is, line );          }            // Ignore comments          line = line.substr( 0, line.find(comm) );            // Parse the line if it contains a delimiter          pos delimPos = line.find( delim );          if( delimPos < string::npos )          {              // Extract the key              string key = line.substr( 0, delimPos );              line.replace( 0, delimPos+skip, "" );                // See if value continues on the next line              // Stop at blank line, next line with a key, end of stream,              // or end of file sentry              bool terminate = false;              while( !terminate && is )              {                  std::getline( is, nextline );                  terminate = true;                    string nlcopy = nextline;                  Config::Trim(nlcopy);                  if( nlcopy == "" ) continue;                    nextline = nextline.substr( 0, nextline.find(comm) );                  if( nextline.find(delim) != string::npos )                      continue;                    nlcopy = nextline;                  Config::Trim(nlcopy);                  if( nlcopy != "" ) line += "\n";                  line += nextline;                  terminate = false;              }                // Store key and value              Config::Trim(key);              Config::Trim(line);              cf.m_Contents[key] = line;  // overwrites if key is repeated          }      }        return is;  }  bool Config::FileExist(std::string filename)  {      bool exist= false;      std::ifstream in( filename.c_str() );      if( in )           exist = true;      return exist;  }    void Config::ReadFile( string filename, string delimiter,                        string comment )  {      m_Delimiter = delimiter;      m_Comment = comment;      std::ifstream in( filename.c_str() );        if( !in ) throw File_not_found( filename );         in >> (*this);  }  

//main.cpp  #include "Config.h"  int main()  {      int port;      std::string ipAddress;      std::string username;      std::string password;      const char ConfigFile[]= "config.txt";       Config configSettings(ConfigFile);            port = configSettings.Read("port", 0);      ipAddress = configSettings.Read("ipAddress", ipAddress);      username = configSettings.Read("username", username);      password = configSettings.Read("password", password);      std::cout<<"port:"<<port<<std::endl;      std::cout<<"ipAddress:"<<ipAddress<<std::endl;      std::cout<<"username:"<<username<<std::endl;      std::cout<<"password:"<<password<<std::endl;            return 0;  }  

Config.txt file content:
IpAddress = 10.10.90.125
Port = 3001
Username = mark
Password = 2d2df5a


Compile and run the output:
Port: 3001
IpAddress: 10.10.90.125
Username: mark
Password: 2d2df5a

There are many other methods in this class. You can call it.