fstream

问题 I'm modifying an project where I want to write an output to a file. In my .hpp file I declared a file stream like so: // fname.hpp file #include <fstream> std::ifstream m_ifs = ("path_to_file"); then on my .cpp file I am have // fname.cpp if (!m_ifs.is_open()) { std::cerr << "Not writing to file" << std::endl; return; } m_ifs << "Write something" But when I compile I get the following error: error: field ‘m_ifs’ has incomplete type ‘std::ifstream {aka std::basic_ifstream<char>}’ /usr/include

问题 I'm modifying an project where I want to write an output to a file. In my .hpp file I declared a file stream like so: // fname.hpp file #include <fstream> std::ifstream m_ifs = ("path_to_file"); then on my .cpp file I am have // fname.cpp if (!m_ifs.is_open()) { std::cerr << "Not writing to file" << std::endl; return; } m_ifs << "Write something" But when I compile I get the following error: error: field ‘m_ifs’ has incomplete type ‘std::ifstream {aka std::basic_ifstream<char>}’ /usr/include

问题 I am generating a CSV file, and of course I get the wonderful trailing comma at the end data1, data2, data3, data1, data2, data3, data1, data2, data3, data1, data2, data3, Can I use the fstream facilities to remove the last comma? I am more familiar with the C fopen and so I'm a bit out of water, and just looking for a quick, best-practices solution. 回答1: The only way to do this with streams is to write your output to a temp buffer / file (e.g. std::stringstream ), and then copy all but the

问题 I am new to C++ and want to write data(integers) on a .txt file. The data is in three or more columns that can be read later for further usage. I have created successfully a reading project but for the writing one the file is created but it is blank. I have tried code samples from multiple sites but is not helping. I have to write results from three different equations as can be seen from the code. #include<iostream> #include<fstream> using namespace std; int main () { int i, x, y; ofstream

问题 Im trying to read a byte file with fstream in c++ (goal: binary data format deserialization). The dat file looks something like below in HxD Hex editor (bytes.dat): but something goes wrong when reading the binary file into a char array.. here is a mwe: #include <iostream> #include <fstream> using namespace std; int main (){ ofstream outfile; outfile.open("bytes.dat", std::ios::binary); outfile << hex << (char) 0x77 << (char) 0x77 << (char) 0x77 << (char) 0x07 \ << (char) 0x9C << (char) 0x04

问题 This question already has an answer here : How to append to a file with fstream fstream::app flag seems not to work (1 answer) Closed 6 years ago . I try to append file in C++. At start file doesn't exists. After operations there is only one line in file instead of five (5 calls of this method). It looks like file is creating, next every write operation file is cleaned out and new string is added. void storeUIDL(char *uidl) { fstream uidlFile(uidlFilename, fstream::app | fstream::ate); if

问题 This question already has an answer here : How to append to a file with fstream fstream::app flag seems not to work (1 answer) Closed 6 years ago . I try to append file in C++. At start file doesn't exists. After operations there is only one line in file instead of five (5 calls of this method). It looks like file is creating, next every write operation file is cleaned out and new string is added. void storeUIDL(char *uidl) { fstream uidlFile(uidlFilename, fstream::app | fstream::ate); if

问题 This question already has an answer here : How to append to a file with fstream fstream::app flag seems not to work (1 answer) Closed 6 years ago . I try to append file in C++. At start file doesn't exists. After operations there is only one line in file instead of five (5 calls of this method). It looks like file is creating, next every write operation file is cleaned out and new string is added. void storeUIDL(char *uidl) { fstream uidlFile(uidlFilename, fstream::app | fstream::ate); if

问题 I need to read a series of numbers from a space-separated human-readable file and do some math, but I've run into some truly bizarre memory behavior just reading the file. If I read the numbers and immediately discard them... #include <fstream> int main(int, char**) { std::ifstream ww15mgh("ww15mgh.grd"); double value; while (ww15mgh >> value); return 0; } My program allocates 59MB of memory according to valgrind, scaling linearly with respect to the size of the file: $ g++ stackoverflow.cpp

来源： https://stackoverflow.com/questions/64598494/getline-ifstream-failure