C ++不从文件中读取任何内容

Question

我好像在读取文件时遇到了问题。我正在使用 Visual Studio Community 2013，它会做除读取文件之外的所有事情。我已经检查以确保正在读取和写入的文件位于同一目录中。以下代码是我认为问题所在：

if (inStream.bad())
{
    inStream.close();

    outStream.open(filename);
    outStream << "This is a test file: \nWelcome to the Dark Side!";
    outStream.close();
}

inStream.open(filename, ios::in);
if (inStream.good())
{
    while (getline(inStream, stream[1]))
    {
        stream[0] += stream[1] + '\n';
    }

    inStream.close();

}
else
{
    cout << "THIS FILE IS ROYALLY *jacked* UP!!!!" << endl;
}

我得到了 "This file is royally jacked up" 结果。我不明白为什么它不读书。请帮忙。

Answer 1

在打开新文件之前使用 clear 可能会有所帮助，因为 open 可能无法自行清除标志。

inStream.clear();
inStream.open(filename, ios::in);

您也可以使用 is_open 而不是 good。

if(inStream.is_open()) {
    ...

Answer 2

尝试调用 inStream.clear() 后再对其进行任何操作。 clear() 清除旧标志，如 bad 为真。

Answer 3

更改行：

if (inStream.bad())
{
    inStream.close();

    outStream.open(filename);
    outStream << "This is a test file: \nWelcome to the Dark Side!";
    outStream.close();
}

inStream.open(filename, ios::in);
if (inStream.good())

至

if (inStream.bad())
{
    inStream.close();

    outStream.open(filename);
    outStream << "This is a test file: \nWelcome to the Dark Side!";
    outStream.close();

    // Clear the state of the stream.
    inStream.clear();

    // Move this line inside the block.
    inStream.open(filename, ios::in);
}

if (inStream.good())

您不想在有效的 ifstream 上调用 open。

这是一个示例程序，演示了在有效 ifstream 上调用 open 可以使其无效。

#include <iostream>
#include <fstream>

int main()
{
   std::ifstream inFile("socc.in");
   if ( inFile.good() )
   {
      std::cout << "ifstream is good.\n";
   }

   inFile.open("socc.in");
   if ( inFile.good() )
   {
      std::cout << "ifstream is still good.\n";
   }
   else
   {
      std::cout << "ifstream is not good any more.\n";
   }

   return 0;
}

输出：

ifstream is good.
ifstream is not good any more.

C ++不从文件中读取任何内容

C++ not reading anything from files

c++

io