Does String Contain

	if (s1.find(s2) != std::string::npos)
		cout << "String found!" << endl;

Do Strings Match

	if (my_string1.compare(my_string2) == 0)		//0=strings are the same
	{
		//Strings match
	}

Does String Start With

	if (CommandResult.find("abc") == 0)

Find first occurrence

	string s1 = "hello world";
	
	if (s1.find(' ') != string::npos)
	{
		cout  << "Space found " << endl;
	}
	else
	{
		cout  << "No spaces found" << endl;
	}

If you want to know where it was found:

	string s1 = "hello world";
	size_t find_result;
		
	if ((find_result = s1.find(' ')) != string::npos)
	{
		cout  << "Space found at character " << find_result << endl;
	}
	else
	{
		cout  << "No spaces found" << endl;
	}

Find last occurance

	string s1 = "hello 12";
	size_t find_result;
		
	if ((find_result = s1.rfind(' ')) != string::npos)	//Searches from the end but still returns an index from the start of the string
	{
		cout  << "Space found at character " << find_result << endl;
	}
	else
	{
		cout  << "No spaces found" << endl;
	}