C++ ifstream 不读\n？
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/15706776/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
C++ ifstream not reading \n?
提问by PulsePanda
I'm doing a project for school, and i have to read a file, and do stuff with it. that isnt important though. i'm supposed to do the operations per line, and the way i have it right now, my ifstream object isnt detecting the '\n'character for each line, which is required for this project. here's how i have it right now:
我正在为学校做一个项目，我必须阅读一个文件，并用它做一些事情。不过这并不重要。我应该按行进行操作，按照我现在的方式，我的 ifstream 对象没有检测到'\n'每个行的字符，这是该项目所需的。这是我现在的方式：
ifstream instream;
instream >> value;
while(value != '\n')
//do code and such
but when i have it run the loop, all i'm getting is a single line of everything in the program. while, it is doing exactly what it is supposed to in the loop, i NEED the \n to be recognized. here's my .txt document:
但是当我让它运行循环时，我得到的只是程序中所有内容的一行。同时，它正在执行循环中应该做的事情，我需要识别 \n。这是我的 .txt 文档：
LXXXVII
cCxiX
MCCCLIV
CXXXLL
MMDCLXXIII
DXLCC
MCdLxxvI
XZ
X
IV
exactly like that. i cannot change it. any assistance as to what i can do would be greatly appreciated! thanks a ton!
正是这样。我不能改变它。任何关于我能做什么的帮助将不胜感激！万分感谢！
EDIT:also, how would i be able to detect when i'm at the end of the file? thanks :D
编辑：另外，我如何能够检测到我何时处于文件末尾？感谢：D
回答by Jonathan Wakely
The >>operator does a "formatted input operation" which means (among other things) it skips whitespace.
所述>>操作者做了“格式的输入操作”它跳过空白其中装置（除其他外）。
To read raw characters one by one without skipping whitespace you need to use an "unformatted input operation" such as istream::get(). Assuming valueis of type char, you can read each char with instream.get(value)
要逐个读取原始字符而不跳过空格，您需要使用“无格式输入操作”，例如istream::get(). 假设value类型为char，您可以读取每个字符instream.get(value)
When you reach EOF the read will fail, so you can read every character in a loop such as:
当您到达 EOF 时，读取将失败，因此您可以读取循环中的每个字符，例如：
while (instream.get(value))
// process value
However, to read line-by-line you could read into a std::stringand use std::getline
但是，要逐行阅读，您可以读入 astd::string并使用std::getline
std::string line;
while (getline(instream, line))
// ...
This is an unformatted input operation which reads everything up to a \ninto the string, then discards the \ncharacter (so you'd need to manually append a \nafter each erad line to reconstruct the original input)
这是一个未格式化的输入操作，它将 a 之前的所有内容读\n入字符串，然后丢弃该\n字符（因此您需要\n在每个 erad 行后手动附加 a以重建原始输入）
回答by taocp
You can read your file as follows:
您可以按如下方式阅读您的文件：
ifstream instream("file.txt);
string line;
while (instream >> line)
{
cout << line;
if (instream.peek() == '\n') //detect "\n"
{
cout <<endl;
}
}
instream.close();
This way you can track where the line in file ends and detect end of file.
通过这种方式，您可以跟踪文件中的行结束位置并检测文件结束位置。
回答by Afterbunny
I guess you are looking for this:
instream.unsetf(std::ios_base::skipws)
我猜你正在寻找这个：
instream.unsetf(std::ios_base::skipws)
