摘自:http://www.cnblogs.com/skunk/archive/2009/05/06/1450912.html
#include <iostream> 2#include <string> 3 4using namespace std; 5int main() 6{ 7 string st="ifn",b; 8 b=st.substr(0,2); 9 cout<<b<<endl; 10 return 0; 11 12}
結果 if
basic_string substr(size_type pos = 0, size_type n = npos) const; The member function returns an object whose controlled sequence is a copy of up to n elements of the controlled sequence beginning at position pos.
substr(start,length);
帶兩個引數,第一個是子串的起始位置(從0開始),第二個是子串的長度