Reading file content opened with ifstream

问题

I have a problem reading file, opened with fstream on windows.

std::ifstream file(file_name);
if(!file.is_open()){
  std::cerr <<  "file cannot be opened";
}
if (!file){
  std::cerr << "errors in file";
}   

std::vector<std::string> strings;
std::string str;
while (std::getline(file, str)) {
  strings.push_back(str);
}

File opened sucessfully and it has no errors, but cycle with getline gets no content.

Besides this sample runs perfect and prints whole file content

std::copy(std::istream_iterator<std::string>(file), std::istream_iterator<std::string>(),
            std::ostream_iterator<std::string>(std::cerr, "\n"));

On linux everything is perfect, same file, same code, getline in cycle reads all.

Visual Studio 2013

Edit:

I forgot to mention that i have this little line of code before cycle with getline

std::cout << file.rdbuf();

On linux this line just prints file content, on windows it not only print, but makes file inacessible to std::getline

回答1:

getline() extracts characters from the input stream until either newline character is reached or delim which is also a character, but instead of only extracting, getline discards the deliminating character. Check your file to see if you started with a newline character, meaning in the file you started on a line other than the first one. If so,

while (std::getline(file, str)) {
  strings.push_back(str);
}

would always iterate only 1 time, returning no characters because it only discarded the newline character.

while (std::getline(file, str) || !file.eof) {
  strings.push_back(str);
}

Will now, if it runs into a deliminating character, also check if the end of the file has been reached.

回答2:

The problem was in calling

std::cout << file.rdbuf();

before while(std::getline) on Windows this line makes file not accessible to std::getline

来源：https://stackoverflow.com/questions/40307840/reading-file-content-opened-with-ifstream

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c++

visual-c++