std::basic_string::append

basic_string& append( size_type count, CharT ch );	(1)
basic_string& append( const basic_string& str );	(2)
	(3)
basic_string& append( const basic_string& str, size_type pos, size_type count );		(until C++14)
basic_string& append( const basic_string& str, size_type pos, size_type count = npos);		(since C++14)
basic_string& append( const CharT* s, size_type count );		(4)
basic_string& append( const CharT* s );		(5)
template< class InputIt > basic_string& append( InputIt first, InputIt last );		(6)
basic_string& append( std::initializer_list<CharT> ilist );		(7)	(since C++11)

Appends additional characters to the string.

1) Appends count copies of character ch.

2) Appends string str.

3) Appends a substring [pos, pos+count) of str. If the requested substring lasts past the end of the string, or if count == npos, the appended substring is [pos, size()). If pos >= str.size(), std::out_of_range is thrown.

4) Appends the first count characters of character string pointed to by s. s can contain null characters.

5) Appends the null-terminated character string pointed to by s. The length of the string is determined by the first null character.

6) Appends characters in the range [first, last).

This overload has the same effect as overload (1) if `InputIt` is an integral type.	(until C++11)
This overload only participates in overload resolution if `InputIt` satisfies `InputIterator`.	(since C++11)

7) Appends characters in the initializer list ilist.

Parameters

count	-	number of characters to append
ch	-	character value to append
first, last	-	range of characters to append
str	-	string to append
s	-	pointer to the character string to append
ilist	-	initializer list with the characters to append

Return value

*this.

Complexity

There are no standard complexity guarantees, typical implementations behave similar to std::vector::insert.

Exceptions

If an exception is thrown for any reason, this function has no effect (strong exception guarantee). (since C++11).

If the operation would result in size() > max_size(), throws std::length_error.

Example

#include <string>
#include <iostream>
 
int main() {
    std::basic_string<char> str = "string";
    const char* cptr = "C-string";
    const char carr[] = "Two and one";
 
    std::string output;
 
    // 1) Repeat a char
    output.append(3, '*');
    std::cout << "1) " << output << "\n";
 
    //  2) Append a whole string
    output.append(str);
    std::cout << "2) " << output << "\n";
 
    // 3) Append part of a string (last 3 letters, in this case)
    output.append(str, 3, 3);
    std::cout << "3) " << output << "\n";
 
    // 4) Append part of a C-string
    // Notice, because `append` returns *this, we can chain calls together
    output.append(1, ' ').append(carr, 4);
    std::cout << "4) " << output << "\n";
 
    // 5) Append a whole C-string
    output.append(cptr);
    std::cout << "5) " << output << "\n";
 
    // 6) Append range
    output.append(&carr[3], std::end(carr));
    std::cout << "6) " << output << "\n";
 
    // 7) Append initializer list
    output.append({ ' ', 'l', 'i', 's', 't' });
    std::cout << "7) " << output << "\n";
}

Output:

1) ***
2) ***string
3) ***stringing
4) ***stringing Two 
5) ***stringing Two C-string
6) ***stringing Two C-string and one
7) ***stringing Two C-string and one list