[英]read text file in C++
I have a question regarding what to do with "\\n"
or "\\r\\n"
etc. when reading a text file in C++. 我在使用C ++读取文本文件时遇到有关如何处理"\\n"
或"\\r\\n"
等问题。 The problem exists when I do the following sequence of operations: 当我执行以下操作序列时,存在问题:
int k;
f>>k;
string line;
getline(f,line);
for an input file with something like 对于具有类似内容的输入文件
1
abc
I have to put a f.get()
in order to read off the ending "\\n"
after f>>k
. 我必须放入f.get()
以便在f>>k
之后读取结尾的"\\n"
。 I even have to do f.get()
twice if I have "\\r\\n"
. 如果我有"\\r\\n"
我甚至必须做两次f.get()
。
What is an elegant way of reading file like this if I mix >>
with getline
? 如果我将>>
和getline
混合使用,那么读取文件的优雅方式是什么?
Thank you. 谢谢。
Edit Also, I wonder if there is any convenient way to automatically detect the given file has an end-of-line char "\\n"
or "\\r\\n"
. 编辑另外,我想知道是否有任何方便的方法来自动检测给定文件的行尾字符为"\\n"
或"\\r\\n"
。
You need to fiddle a little bit to >>
and getline
to work happily together. 您需要花一点时间去>>
和getline
一起快乐地工作。 In general, reading something from a stream with the >>
operator will not discard any following whitspaces (new line characters). 通常,使用>>
运算符从流中读取内容不会丢弃任何后续的空格(换行符)。
The usual approach to solve this is with the istream::ignore
function following >>
- telling it to discard every character up to and including the next newline. 解决此问题的常用方法是使用>>
的istream::ignore
函数-告诉它丢弃直到下一个换行符的所有字符。 (Only useful if you actually want to discard every character up to the newline though). (仅在您实际上要舍弃换行符之前的每个字符时才有用)。
eg 例如
#include <iostream>
#include <string>
#include <limits>
int main()
{
int n;
std::string s;
std::cout << "type a number: ";
std::cin >> n;
std::cin.ignore( std::numeric_limits<std::streamsize>::max(), '\n' );
std::cout << "type a string: ";
std::getline( std::cin, s );
std::cout << s << " " << n << std::endl;
}
edit (I realise you mentioned files in the question, but hopefully it goes without saying that std::cin is completely interchangable with an ifstream) 编辑 (我意识到您在问题中提到了文件,但希望它不用说std :: cin与ifstream完全可互换)
完全不同的方法是使用tr
预处理数据文件(假设您使用Linux)删除\\r
,然后使用getline()
。
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.