#include <string>
using namespace std;
...
string first_name = "Bjarne";
string last_name;

last_name = "Stroustrup";

string names = first_name + " " + last_name;
cout << names << endl;

names = last_name + ", " + first_name;
cout << names << endl; 

string str1; 

A string object may also be initialized with

• a string expression:

  string str2 = str1;
  string str3 = str1 + str2;
  string str4 (str2);  // Alternate form 

• a character string literal:

  string str4 = "Hello there";
  string str5 ("Goodbye");  // Alternate form 

• a single character
  Unfortunately, the expected methods don't work:

  string str6 = 'A';  // Incorrect
  string str7 ('A');  // Also incorrect

  Instead, we must use a special form with two values:

  string str7 (1,'A'); // Correct

  The two values are the desired length of the string and a character to fill the string with. In this case, we are asking for a string of length one, filled with the character A.

• a substring of another string object:

  string str8 = "ABCDEFGHIJKL";
  // Initialize str9 as "CDEFG"
  // Starts at character 2 ('C')
  // with a length of 5
  // (or the rest of the string, if shorter)
  string str9 (str8,2,5); 

size

string str = "Hello";
string::size_type len;
len = str.length(); // len == 5 
len = str.size();   // len == 5 

string filename;
cout << "Enter file name: ";
cin >> filename;
ofstream outfile (filename.c_str());
outfile << "Data" << endl; 

string str11 = "abcdefghi";
string str12 = "0123";
str11.insert (3,str12);
cout << str11 << endl; // "abc0123defghi"
str12.insert (1,"XYZ");
cout << str12 << endl; // "0XYZ123" 

string str13 = "abcdefghi";
str12.erase (5,3);
cout << str12 << endl; // "abcdei" 

string str14 = "abcdefghi";
string str15 = "XYZ";
str14.replace (4,2,str15);
cout << str14 << endl; // "abcdXYZghi" 

Note: if you want to replace only a single character at a time, you should use the subscript operator ([]) instead.

rfind

string str16 = "abcdefghi";
string str17 = "def";
string::size_type pos = str16.find (str17,0);
cout << pos << endl; // 3
pos = str16.find ("AB",0);
if (pos == string::npos) cout << "Not found" << endl;

find_first_not_of

find_last_of

find_last_not_of

string str20 = "Hello there";
string str21 = "aeiou";
pos = str20.find_first_of (str21, 0);
cout << pos << endl; // 1
pos = str20.find_last_not_of ("eHhlort");
cout << pos << endl; // 5

string str18 = "abcdefghi"
string str19 = str18.substr (6,2);
cout << str19 << endl; // "gh" 

Note: if you want to retrieve only a single character at a time, you should use the subscript operator ([]) instead.

end

Iterators are special objects that are used in many STL algorithms.

• An end-of-file condition occurs on the input stream
• When the maximum number of characters that can fit into a string have been read
• When a character read in from the string is equal to the specified delimiter (newline is the default delimiter); the delimiter character is removed from the input stream, but not appended to the string.

The return value is a reference to the input stream. If the stream is tested as a logical value (as in an if or while), it is equivalent to true if the read was successful and false otherwise (e.g., end of file). [Note: some libraries do not implement getline correctly for use with keyboard input, requiring that an extra "carriage return" be entered to terminate the read. Some patches are available.]

The most common use of this function is to do "line by line" reads from a file. Remember that the normal extraction operator (>>) stops on white space, not necessarily the end of an input line. The getline function can read lines of text with embedded spaces.

vector<string> vec1;
string line;
vec1.clear();
ifstream infile ("stl2in.txt");
while (getline(infile,line,'\n'))
{
  vec1.push_back (line);
}

This STL algorithm (from the <algorithm> library) is a little tricky, but simple uses are easy. For example, we can iterate through the characters in a string, modifying them in some way, and returning the modified characters back to their original positions. In this case, we set the result iterator to specify the beginning of the string. A common application is to convert a string to upper or lower case.

string str22 = "This IS a MiXed CaSE stRINg";
transform (str22.begin(),str22.end(), str22.begin(), tolower);
cout << "[" << str22 << "]" << endl; // [this is a mixed case string]

Note that the result iterator must specify a destination that is large enough to accept all the modified values; here it is not a problem, since we're putting them back in the same positions. The tolower function (along with toupper, isdigit, and other useful stuff) is in the <cctype> library; for more general case conversions, take a look at the <locale> library, which is beyond the scope of the present discussion.

• Assigning one string object's value to another string object

  string string_one = "Hello";
  string string_two;
  string_two = string_one; 

• Assigning a C++ string literal to a string object

  string string_three;
  string_three = "Goodbye"; 

• Assigning a single character (char) to a string object

  string string_four;
  char ch = 'A';
  string_four = ch;
  string_four = 'Z'; 

• two string objects

  string str1 = "Hello ";
  string str2 = "there";
  string str3 = str1 + str2; // "Hello there" 

• a string object and a character string literal

  string str1 = "Hello ";
  string str4 = str1 + "there"; 

• a string object and a single character

  string str5 = "The End";
  string str6 = str5 + '!'; 

• two string objects
• a string object and a character string literal

(subscript)