c++ : 获得string的子串

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}

结果   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);

带两个参数，第一个是子串的起始位置（从0开始），第二个是子串的长度