how to clear a string in c 2b 2b

1str.clear(); 
2

1 string& erase (size_t pos = 0, size_t len = npos);
2/*
3pos
4Position of the first character to be erased.
5If this is greater than the string length, it throws out_of_range.
6Note: The first character in str is denoted by a value of 0 (not 1).
7len
8Number of characters to erase (if the string is shorter, as many characters as possible are erased).
9A value of string::npos indicates all characters until the end of the string.
10*/