[英]ifstream from next/new line in c++
I am having set of data stored in a file which are basically names.我将一组数据存储在一个基本上是名称的文件中。 My task is to get all the first letters from each name.我的任务是获取每个名字的所有首字母。 Here is the file:这是文件:
Jack fisher
goldi jones
Kane Williamson
Steaven Smith
I want to take out just first word from each line(ex. jack, goldi, kane, Steaven) I wrote following code for it, just to take take out 2 names.我想从每行中取出第一个单词(例如,jack、goldi、kane、Steaven)我为它编写了以下代码,只是为了取出 2 个名字。 Here it is:这里是:
string first,last;
ifstream Name_file("names.txt");
Name_file>>first;
Name_file>>endl;
Name_file>>last;
cout<<first<<" "<<last;
it is giving error.它给出了错误。 If I remove endl, it takes the first full name(Jack, fisher) whereas I want it should take (jack,goldi).如果我删除 endl,它会采用第一个全名(Jack,fisher),而我希望它应该采用(jack,goldi)。 How to do it?怎么做? Any idea?任何想法? Thanks in advance for help.提前感谢您的帮助。
Name_file>>endl;
is always wrong.总是错的。
Even then, you can't use >>
like that, it will stop on a space, which is why when you remove endl
you see the problem that first
and last
contain only the first line.即使那样,您也不能像这样使用>>
,它会停在一个空格上,这就是为什么当您删除endl
时,您会看到first
和last
仅包含第一行的问题。
Use std::getline
to loop over your file instead and get the full names, then split the line on the first space to get the first name:使用std::getline
来遍历您的文件并获取全名,然后在第一个空格处拆分该行以获取名字:
ifstream Name_file("names.txt");
std::string line;
while (std::getline(Name_file, line))
{
std::string firstName = line.substr(0, line.find(' '));
//do stuff with firstName..
}
Though I don't mind "Hatted Rooster"implementation I think it can be a little less efficient when the input suddenly contains a very long line.虽然我不介意“戴帽公鸡”的实现,但我认为当输入突然包含很长的行时,它的效率可能会降低一些。
I would use ignore()
to remove the rest of the line:我将使用ignore()
删除该行的 rest:
int main()
{
std::ifstream nameFile("names.txt");
std::string firstName;
while (nameFile >> firstName)
{
// You got a first name.
// Now dump the remaing part of the line.
nameFile.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
}
}
I hope this solves your query.我希望这能解决您的疑问。
ifstream Name_file;
string line;
Name_file.open("names.txt");
if(Name_file.fail()){ cerr<<"Error opening file names.txt !!"<<endl;return;}
vector<string> v; // array to store file names;
while(Name_file >> line){
string word;
getline(Name_file, word);
v.push_back(line);
}
// printing the first names
for(int i = 0; i < v.size();i++){
cout<<v[i]<<endl;
}
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