For file positions they are the same. In other words there is only one pointer maintained. From 27.9.1.1p3: A joint file position is maintained for both the input sequence and the output sequence. So, seekg and seekp are interchangeable for file streams. However, this is not true for other types of streams, as they may … Read more
According to the standard 27.9.1.11 basic_ofstream constructors or, its more “readable” version http://en.cppreference.com/w/cpp/io/basic_ofstream/basic_ofstream , std::basic_ostream<> has a move constructor, so the code should compile. clang++ 3.5 compiles it with -std=c++11 or -std=c++1y. Also gcc5 compiles it, so probably it is not implemented in libstdc++ for gcc < 5 Interestingly, the lack of move semantics is … Read more
Clion looks for input files and writes output files to the Debug folder. If you put your input files in there it will see them.
This is one of my favorite tuck-away functions I keep on hand for multiple uses. #include <sys/stat.h> // Function: fileExists /** * Check if a file exists * * @param[in] filename – the name of the file to check * * @return true if the file exists, else false */ bool fileExists(const std::string& filename) { … Read more
How about this :- std::ifstream inFile(“file”); std::count(std::istreambuf_iterator<char>(inFile), std::istreambuf_iterator<char>(), ‘\n’);
An istream treats “white space” as delimiters. It uses a locale to tell it what characters are white space. A locale, in turn, includes a ctype facet that classifies character types. Such a facet could look something like this: #include <locale> #include <iostream> #include <algorithm> #include <iterator> #include <vector> #include <sstream> class my_ctype : public … Read more
ios::out opens the file for writing. ios::binary makes sure the data is read or written without translating new line characters to and from \r\n on the fly. In other words, exactly what you give the stream is exactly what’s written.
Simplest form: std::string line; std::vector<std::string> myLines; while (std::getline(myfile, line)) { myLines.push_back(line); } No need for crazy c thingies 🙂 Edit: #include <iostream> #include <fstream> #include <string> #include <vector> int main() { std::string line; std::vector<std::string> DataArray; std::vector<std::string> QueryArray; std::ifstream myfile(“OHenry.txt”); std::ifstream qfile(“queries.txt”); if(!myfile) //Always test the file open. { std::cout<<“Error opening output file”<< std::endl; system(“pause”); return … Read more
I don’t think you can get “atomic” operation but using the Filesystem Technical Specification that has now been accepted as part of the Standard Library (C++17) you can resize the file like this: #include <fstream> #include <sstream> #include <iostream> #include <experimental/filesystem> // compilers that support the TS // #include <filesystem> // C++17 compilers // for … Read more
You should add fstream::out to open method like this: file.open(“test.txt”,fstream::out); More information about fstream flags, check out this link: http://www.cplusplus.com/reference/fstream/fstream/open/