C++ Gezielt Daten aus txt einlesen

# z.B.
file="$1"

echo -n "ID: "
read id
echo -n "Current record: "
egrep "^$id;" "$file"

echo -n "New Title: "
read title
echo -n "New Autor: "
read autor
echo -n "New number: "
read number

content=$(cat "$file")
sed "s/^$id;.*$/$id;$title;$autor;$number/" <<< "$content" > "$file"

int id = 3;
Datensatz tempDatensatz;
m_db.getDatensatz(id, &tempDatensatz);

// Und die Klasse DB hat dann als Member
void DB::getDatensatz(int id, Datensatz* daten)
{
  std::map<int, Datensatz>::iterator it = m_data.find(id);
  if (it != m_data.end()) // id wurde gefunden
    daten = it;
  else // id wurde nicht gefunden
    daten = NULL;
}

int ReadFile(char *filename)
{
	fstream myFile;
	myFile.open(filename);

	if (myFile.is_open())
	{
		char line[500];

		//Parse object file line by line
		while (myFile.good())
		{
			myFile.getline(line,500);
                        int i;
                        string s1;
                        string s2;
			string s3;

			sscanf(line,"%d;%s;%s;%s", &i, &s1, &s2,&s3);
			
		}

		myFile.close();

	}
	else
	{
		cout << "Konnte Datei '" << filename << "' nicht lesen. \n";
		return false;
	}

	return true;
}

_CRT_SECURE_NO_WARNINGS

#include <string>
#include <vector>
#include <fstream>
#include <iostream>

std::vector<std::string> split_string(const std::string& str,
                                      const std::string& delimiter)
{
    std::vector<std::string> strings;

    std::string::size_type pos = 0;
    std::string::size_type prev = 0;
    while ((pos = str.find(delimiter, prev)) != std::string::npos)
    {
        strings.push_back(str.substr(prev, pos - prev));
        prev = pos + 1;
    }

    // To get the last substring (or only, if delimiter is not found)
    strings.push_back(str.substr(prev));

    return strings;
}

std::vector< std::string > parse_CSV_line( const std::string& line, char delimiter )
{
	bool inQuotes = false;
	std::string currentValue;
	std::vector< std::string > record;

	for ( std::string::size_type i = 0; i < line.length(); ++i )
	{
		const char currentChar = line[ i ];

		if ( ! inQuotes && currentValue.empty() && currentChar == '"' )
		{
			inQuotes = true;
		}
		else if ( inQuotes && currentChar == '"' )
		{
			if ( i + 1 < line.length() && line[ i + 1 ] == '"' )
			{
				currentValue.push_back( currentChar );
				++i;
			}
			else
			{
				inQuotes = false;
			}
		}
		else if ( ! inQuotes )
		{
			if ( currentChar == delimiter )
			{
				record.push_back( currentValue );
				currentValue.clear();
			}
			else if ( currentChar == '\r' || currentChar == '\n' )
			{
				record.push_back( currentValue );
				return record;
			}
			else
			{
				currentValue.push_back( currentChar );
			}
		}
		else
		{
			currentValue.push_back( currentChar );
		}
	}

	record.push_back( currentValue );

	return record;
}

std::string readFileIntoString( const std::string& fileName )
{
	std::ifstream ifs( fileName, std::ios::in );

	if ( ! ifs )
	{
		std::cerr << "Failed to open file for reading!\n";
		return std::string();
	}

	return std::string( ( std::istreambuf_iterator< char >( ifs ) ), std::istreambuf_iterator< char >() );
}

int main()
{
	const std::string fileContent = readFileIntoString( "D:\\tmp\meineDatei.txt" );

	if ( fileContent.empty() )
	{
		// war wohl nix
		return 1;
	}

	const std::vector< std::string > lines = split_string( fileContent, "\n" );

	for ( auto it = lines.begin(); it != lines.end(); ++it )
	{
		const std::vector< std::string > fieldsInThisLine = parse_CSV_line( *it, ';' );

		const std::string id_string = fieldsInThisLine.at( 0 );
		const std::string title_string = fieldsInThisLine.at( 1 );
		const std::string author_string = fieldsInThisLine.at( 2 );

		// ...
	}

	return 0;
}