C++這個函數有什麼問題

Question

void webparser(const string siteurl,string filename) 
{ 
    stringstream ss; 
    ss << "lynx -dump '" << siteurl << "'" > filename; 
    system(ss.str().c_str()); 
} 

如何在上面的例子中使用filename而不是file.txt？

最初我對SS線是

ss << "lynx -dump '" << siteurl << "' > file.txt"; 

但我決定改變它從參數使用的價值，所以我增加了文件名。

下面是我的錯誤信息

main.cpp: In function ‘void webparser(std::string, std::string)’: 
main.cpp:244:46: error: no match for ‘operator>’ in ‘std::operator<< [with _Traits = std::char_traits<char>]((* & std::operator<< [with _CharT = char, _Traits = std::char_traits<char>, _Alloc = std::allocator<char>]((* & std::operator<< [with _Traits = std::char_traits<char>]((* & ss.std::basic_stringstream<char>::<anonymous>.std::basic_iostream<char>::<anonymous>), ((const char*)"lynx -dump \'"))), (* & siteurl))), ((const char*)"\'")) > filename’ 
main.cpp:244:46: note: candidates are: 
/usr/include/c++/4.6/bits/stl_pair.h:220:5: note: template<class _T1, class _T2> bool std::operator>(const std::pair<_T1, _T2>&, const std::pair<_T1, _T2>&) 
/usr/include/c++/4.6/bits/stl_iterator.h:303:5: note: template<class _Iterator> bool std::operator>(const std::reverse_iterator<_Iterator>&, const std::reverse_iterator<_Iterator>&) 
/usr/include/c++/4.6/bits/stl_iterator.h:353:5: note: template<class _IteratorL, class _IteratorR> bool std::operator>(const std::reverse_iterator<_IteratorL>&, const std::reverse_iterator<_IteratorR>&) 
/usr/include/c++/4.6/bits/basic_string.h:2547:5: note: template<class _CharT, class _Traits, class _Alloc> bool std::operator>(const std::basic_string<_CharT, _Traits, _Alloc>&, const std::basic_string<_CharT, _Traits, _Alloc>&) 
/usr/include/c++/4.6/bits/basic_string.h:2559:5: note: template<class _CharT, class _Traits, class _Alloc> bool std::operator>(const std::basic_string<_CharT, _Traits, _Alloc>&, const _CharT*) 
/usr/include/c++/4.6/bits/basic_string.h:2571:5: note: template<class _CharT, class _Traits, class _Alloc> bool std::operator>(const _CharT*, const std::basic_string<_CharT, _Traits, _Alloc>&) 
/usr/include/c++/4.6/bits/stl_iterator.h:842:5: note: template<class _Iterator, class _Container> bool __gnu_cxx::operator>(const __gnu_cxx::__normal_iterator<_Iterator, _Container>&, const __gnu_cxx::__normal_iterator<_Iterator, _Container>&) 
/usr/include/c++/4.6/bits/stl_iterator.h:836:5: note: template<class _IteratorL, class _IteratorR, class _Container> bool __gnu_cxx::operator>(const __gnu_cxx::__normal_iterator<_IteratorL, _Container>&, const __gnu_cxx::__normal_iterator<_IteratorR, _Container>&) 
make: *** [main.o] Error 1 

Answer 1

更換

ss << "lynx -dump '" << siteurl << "'" > filename; 

與

ss << "lynx -dump '" << siteurl << "'" << filename; 

，或者是與你原來的代碼是一致的：

ss << "lynx -dump '" << siteurl << "' > " << filename;