You can simply do this: int devices::open_file(std::string _file_name) { ifstream input_stream; input_stream.open(_file_name.c_str(), ios::in); if(!input_stream) { return -1; } file_name = _file_name; return 0; } fail() is not a static method, you must call it on an instance not a type, so if you want to use fail(), replace !input_stream with input_stream.fail() in my code above. … Read more
INTRODUCTION std::ifstream::fail includes checking std::ifstream::is_open, but std::ifstream::is_open only checks if it was possible to create a handle to the file. EXPLANATION std::ifstream::fail can return true, even if std::ifstream::is_open returns true; they are not the mutually exclusive. .fail will check the overall “health” of the stream, which involves things such as checking the stream has currently … Read more
You cannot do that just in standard C++, since iostreams and C I/O are entirely separate and unrelated. You could however write your own iostream that’s backed by a C FILE stream. I believe that GCC comes with one such stream class as a library extension. Alternatively, if all you want is an object-y way … Read more
The boolean conversion operator for std::basic_istream is explicit. This means that instances of the type will not implicitly become a bool but can be converted to one explicitly, for instance by typing bool(infile). Explicit boolean conversion operators are considered for conditional statements, i.e. the expression parts of if, while etc. More info about contextual conversions … Read more
tellg does not report the size of the file, nor the offset from the beginning in bytes. It reports a token value which can later be used to seek to the same place, and nothing more. (It’s not even guaranteed that you can convert the type to an integral type.) At least according to the … Read more
How about this :- std::ifstream inFile(“file”); std::count(std::istreambuf_iterator<char>(inFile), std::istreambuf_iterator<char>(), ‘\n’);
You need to initialize it through the member-initializer list: A::A(std::string filename) : file(new std::ifstream(filename)); { } Your example was an attempt to call operator () on a unique_ptr which is not possible. Update: BTW, C++14 has std::make_unique: A::A(std::string filename) : file(std::make_unique<std::ifstream>(filename)); { }
-1 is get‘s way of saying you’ve reached the end of file. Compare it using the std::char_traits<char>::eof() (or std::istream::traits_type::eof()) – avoid -1, it’s a magic number. (Although the other one is a bit verbose – you can always just call istream::eof) The EOF flag is only set once a read tries to read past the … Read more
You’re missing #include <fstream> and you probably assign somthing to inFile which is not allowed.
Use the std::getline() from <string>. istream & getline(istream & is,std::string& str) So, for your case it would be: std::getline(read,x);