在文件夹中的txt文件列表中搜索“关键字”，如果找到“关键字”（批量脚本），则将txt文件移动到另一个文件夹(Search “keyword” in a list of txt file in a folder and move txt file to another folder if “keyword” is found (batch scripting))

 strlen()用于C const char*字符串。 要获取字符串s的长度，请使用s.size()或s.length() 。 如果要从string获取C string ，请使用s.c_str() 。 
 
 虽然C ++ 看起来 const char*和string是可以互换的，但只有在将const char*转换为string时才会采用一种方式。 
 
 你没有理由想要使用strlen 。 strlen最有可能用循环定义，它永远不会像size() ，而大多数只是string类的长度属性的getter。 在调用没有C ++替代方法的C函数时，只将string转换为C字符串。 

strlen() is for C const char* strings. To get the length of a string s, use s.size() or s.length(). If you want to get a C string from a string, use s.c_str().
 
Although C++ makes it seem that const char* and string are interchangeable, that only goes one way when converting const char* to string.
 
There is no reason why you would want to use strlen either. strlen is most likely defined with a loop, which will never be as efficiant as size(), which is most likley just a getter for a length property of the string class. Only convert string to C strings when calling C functions for which there is not a C++ alternative.