ifstream，行尾并移至下一行？

发布于 2024-07-12 19:27:42 字数 502 浏览 6 评论 0原文

如何使用 std::ifstream 检测并移动到下一行？

void readData(ifstream& in)
{
    string sz;
    getline(in, sz);
    cout << sz <<endl;
    int v;
    for(int i=0; in.good(); i++)
    {
        in >> v;
        if (in.good())
            cout << v << " ";
    }
    in.seekg(0, ios::beg);
    sz.clear();
    getline(in, sz);
    cout << sz <<endl; //no longer reads
}

我知道如果发生错误，好的会告诉我，但一旦发生错误，流就不再工作。在读取另一个 int 之前，如何检查我是否位于行尾？

原文

how do i detect and move to the next line using std::ifstream?

void readData(ifstream& in)
{
    string sz;
    getline(in, sz);
    cout << sz <<endl;
    int v;
    for(int i=0; in.good(); i++)
    {
        in >> v;
        if (in.good())
            cout << v << " ";
    }
    in.seekg(0, ios::beg);
    sz.clear();
    getline(in, sz);
    cout << sz <<endl; //no longer reads
}

I know good would tell me if an error happened but the stream no longer works once that happens. How can i check to see if i am at the end of line before reading another int?

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请爱~陌生人 2024-07-19 19:27:47

您应该在循环后使用 in.clear(); 清除流的错误状态，然后流将再次工作，就好像没有发生错误一样。

您还可以将循环简化为：

while (in >> v) {
  cout << v << " ";
}
in.clear();

如果操作成功，则流提取将返回，因此您可以直接测试它，而无需显式检查 in.good();。

You should clear the error state of the stream with in.clear(); after the loop, then the stream will work again as if no error happened.

You might also simplify your loop to:

while (in >> v) {
  cout << v << " ";
}
in.clear();

The stream extraction returns if the operation succeeded, so you can test this directly without explicitly checking in.good();.

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萌能量女王 2024-07-19 19:27:46

使用ignore() 忽略所有内容，直到下一行：

 in.ignore(std::numeric_limits<std::streamsize>::max(), '\n')

如果您必须手动执行此操作，只需检查其他字符以查看是否为'\n'

char next;
while(in.get(next))
{
    if (next == '\n')  // If the file has been opened in
    {    break;        // text mode then it will correctly decode the
    }                  // platform specific EOL marker into '\n'
}
// This is reached on a newline or EOF

这可能会失败，因为您在清除坏位之前进行了查找。

in.seekg(0, ios::beg);    // If bad bits. Is this not ignored ?
                          // So this is not moving the file position.
sz.clear();
getline(in, sz);
cout << sz <<endl; //no longer reads

Use ignore() to ignore everything until the next line:

 in.ignore(std::numeric_limits<std::streamsize>::max(), '\n')

If you must do it manually just check othe character to see if is '\n'

char next;
while(in.get(next))
{
    if (next == '\n')  // If the file has been opened in
    {    break;        // text mode then it will correctly decode the
    }                  // platform specific EOL marker into '\n'
}
// This is reached on a newline or EOF

This is probably failing because you are doing a seek before clearing the bad bits.

in.seekg(0, ios::beg);    // If bad bits. Is this not ignored ?
                          // So this is not moving the file position.
sz.clear();
getline(in, sz);
cout << sz <<endl; //no longer reads

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