为什么我的删除字符串尝试失败

Question

我一直在尝试制作我自己的这个例子：

Delete a specific line from a file

但我无法让我的工作正常。我目前对该程序的目标是删除字符串及其信息（即第一个字符串下方的字符串），它会这样做；但是，它还在第一行添加了一个额外的空间，使其看起来像这样：

(First Line)


(Second Line) This should be the first line.

代码如下：

infile = ifstream;
outfile = ofstream;
cout<< "What string would you like to delete";
cin>>delstr;
infile.clear();
infile.seekg(0, ios::beg);

ofstream tempfile;
tempfile.open("temp.txt",std::ios::app);

while(delreset == true){

    if(delstr == fLine){
        getline(infile, fLine);

        cout<<"String deleted.\n";
        delreset = false;

        while(fLine != nothing){
            getline(infile, fLine);
            tempfile<<fLine<<"\n";
        }

        tempfile.close();
        infile.close();
        outfile.close();
        remove("example.txt");
        rename("temp.txt","example.txt");

    }else{

        tempfile<<fLine<<endl;
        getline(infile, fLine);

    }
    outfile.flush();
    delreset = true;
}

我删除了我所能做的，使它成为实际程序的删节版本，希望我没有编辑任何东西，所以它没有意义。

Answer 1

更简单的版本：

...  // prepare everything as before
while(getline(infile, fLine)) {
    if(delstr == fLine) {   // if line found do nothing
        cout<<"String deleted.\n";
        getline(infile, fLine);  // EDIT: and read and ignore the following line 
    }
    else 
        tempfile<<fLine<<"\n";  // else copy it 
}
...  // here infile was read and tempfile contains the filtered output 

使用这种方法，您甚至可以直接写入输出文件。

顺便说一句cin>>delstr; 只需要一个字。它在第一个空格处停止并忽略尾随空格。您可以改用getline(cin, delstr);。

Answer 2

尝试类似的方法：

cout << "What string would you like to delete";
getline(cin, delstr);
bool deleted = false;

infile.clear();
infile.seekg(0, ios::beg);

ofstream tempfile;
tempfile.open("temp.txt", std::ios::app);

while (getline(infile, fLine))
{
    if ((!deleted) && (fLine == delstr))
    {
        getline(infile, fLine);
        cout << "String deleted." << endl;
        deleted = true;
    }
    else
        tempfile << fLine << endl;
}

tempfile.close();
infile.close();
outfile.close();

if (deleted)
{
    remove("example.txt");
    rename("temp.txt", "example.txt");
}
else
    remove("temp.txt");