如果是fstream定義的物件，則seekg()和seekp()是一樣的功能，還有tellp和tellg

seekg是從ifstream類裡繼承來的

seekp是從ofstream類繼承來的

兩者的功能在fstream裡都是定位讀寫指標

	char s1[30]={'\0'};
	fstream f1("1.txt",ios::out);
	f1<<"this is a program!\n";
	f1<<"hello\n";
	cout << f1.tellg()<<endl;
	
	cout << f1.tellp()<<endl;
	f1.close();
	char s2[30]={'\0'};
	fstream f2("1.txt",ios::in);
	cout<<f2.tellg()<<endl;
	cout<<f2.tellp()<<endl;
	f2.seekp(-25,ios::end);	
	f2.getline(s1,20);
	cout<<f2.tellp()<<endl;

	f2.seekg(10,ios::beg);
	f2.getline(s2,10);

	f2.close();
	cout<<s1<<endl;
	cout<<s2<<endl;