std::string::append() in C++

This member function appends characters in the end of string.

1. Syntax 1 : Appends the characters of string str. It Throws length_error if the resulting size exceeds the maximum number of characters.

   string& string::append (const string& str)
   
   str :  is the string to be appended.
   Returns :  *this

   // CPP code to demonstrate append(str)
   
   #include <iostream>
   #include <string>
   using namespace std;
   
   // Function to demonstrate append()
   void appendDemo(string str1, string str2)
   {
       // Appends str2 in str1
       str1.append(str2);
       cout << "Using append() : ";
       cout << str1 << endl;
   }
   
   // Driver code
   int main()
   {
       string str1("Hello World! ");
       string str2("GeeksforGeeks");
   
       cout << "Original String : " << str1 << endl;
       appendDemo(str1, str2);
   
       return 0;
   }

   Output:

   Original String : Hello World! 
   Using append() : Hello World! GeeksforGeeks
   

2. Syntax 2 : Appends at most, str_num characters of string str, starting with index str_idx. It throws out_of_range if str_idx > str. size(). It throws length_error if the resulting size exceeds the maximum number of characters.

   string& string::append (const string& str, size_type str_idx, size_type str_num)
   
   str : is the string to be appended
   str_num : being number of characters
   str_idx : is index number.
   Returns : *this.
   

   // CPP code to demonstrate
   // append(const char* chars, size_type chars_len)
   
   #include <iostream>
   #include <string>
   using namespace std;
   
   // Function to demonstrate append()
   void appendDemo(string str1, string str2)
   {
       // Appends 5 characters from 0th index of
       // str2 to str1
       str1.append(str2, 0, 5);
       cout << "Using append() : ";
       cout << str1;
   }
   
   // Driver code
   int main()
   {
       string str1("GeeksforGeeks ");
       string str2("Hello World! ");
   
       cout << "Original String : " << str1 << endl;
       appendDemo(str1, str2);
   
       return 0;
   }

   Output:

   Original String : GeeksforGeeks 
   Using append() : GeeksforGeeks Hello
   

3. Syntax 3: Appends the characters of the C-string cstr. Throw length_error if the resulting size exceeds the maximum number of characters.

   string& string::append (const char* cstr)
   
   *cstr : is the pointer to C-string.
   Note : that cstr may not be a null pointer (NULL).
   Return : *this
   

   // CPP code to demonstrate append(const char* cstr)
   
   #include <iostream>
   #include <string>
   using namespace std;
   
   // Function to demonstrate append
   void appendDemo(string str)
   {
       // Appends "GeeksforGeeks"
       // in str
       str.append("GeeksforGeeks");
       cout << "Using append() : ";
       cout << str << endl;
   }
   
   // Driver code
   int main()
   {
       string str("World of ");
   
       cout << "Original String : " << str << endl;
       appendDemo(str);
   
       return 0;
   }

   Output:

   Original String : World of 
   Using append() : World of GeeksforGeeks
   

4. Syntax 4: Appends chars_len characters of the character array chars. Throws length_error if the resulting size exceeds the maximum number of characters.

   string& string::append (const char* chars, size_type chars_len)
   
   *chars is the pointer to character array to be appended.
   chrs_len : is the number of characters from *chars to be appended.
   Note that chars must have at least chars_len characters. 
   Returns : *this.
   

   // CPP code to demonstrate
   // (const char* chars, size_type chars_len)
   
   #include <iostream>
   #include <string>
   using namespace std;
   
   // Function to demonstrate append
   void appendDemo(string str)
   {
       // Appends 5 characters from "GeeksforGeeks"
       // to str
       str.append("GeeksforGeeks", 5);
       cout << "Using append() : ";
       cout << str << endl;
   }
   
   // Driver code
   int main()
   {
       string str("World of ");
   
       cout << "Original String : " << str << endl;
       appendDemo(str);
   
       return 0;
   }

   Output:

   Original String : World of 
   Using append() : World of Geeks
   

5. Syntax 5: Appends num occurrences of character c. Throws length_error if the resulting size exceeds the maximum number of characters.

   string& string::append (size_type num, char c)
   
   num : is the number of occurrences
   c : is the character which is to be appended repeatedly. 
   Returns : *this.
   

   // CPP code to illustrate
   // string& string::append (size_type num, char c)
   
   #include <iostream>
   #include <string>
   using namespace std;
   
   // Function to demonstrate append
   void appendDemo(string str)
   {
       // Appends 10 occurrences of '$'
       // to str
       str.append(10, '$');
       cout << "After append() : ";
       cout << str;
   
   }
   
   // Driver code
   int main()
   {
       string str("#########");
   
       cout << "Original String : " << str << endl;
       appendDemo(str);
   
       return 0;
   }

   Output:

   Original String : #########
   After append() : #########$$$$$$$$$$
   

6. Syntax 6: Appends all characters of the range [beg, end). Throws length_error if the resulting size exceeds the maximum number of characters.

   string& string::append (InputIterator beg, InputIterator end)
   
   first, last : Input iterators to the initial and final positions 
   in a sequence.
   Returns *this.
   

   // CPP code  to illustrate
   // append (InputIterator beg, InputIterator end)
   
   #include <iostream>
   #include <string>
   using namespace std;
   
   // Function to demonstrate append
   void appendDemo(string str1, string str2)
   {
   
       // Appends all characters from
       // str2.begin()+5, str2.end() to str1
       str1.append(str2.begin() + 5, str2.end());
       cout << "Using append : ";
       cout << str1;
   }
   // Driver code
   int main()
   {
       string str1("Hello World! ");
       string str2("GeeksforGeeks");
   
       cout << "Original String : " << str1 << endl;
       appendDemo(str1, str2);
   
       return 0;
   }

   Output:

   Original String : Hello World! 
   Using append : Hello World! forGeeks
   

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