Getline to String复制换行符 [英] Getline to String Copies newline as well

问题描述

我正在逐行读取文件，并将每行添加到字符串。然而，字符串长度增加1每一行，我相信是由于换行符。如何删除它被复制。

I am reading a file line by line and adding each line to a string. However the string length increases by 1 for every line which I believe is due to newline character. How can I remove it from being copied.

这里是我的代码尝试做同样的。

Here is my code attempt to do the same.

if (inputFile.is_open())
{
    {
        string currentLine;
        while (!inputFile.eof())
            while( getline( inputFile, currentLine ) )
            {
                string s1=currentLine;
                cout<<s1.length();
            }

[更新说明]我使用notepad ++来确定我的长度逐行选择。所以他们显示一些123，450，500，120，我的程序显示124,451,501,120。除了最后一行，所有的line.length（）显示一个增加的值。

[Updated Description] i have used notepad++ to determine the length of what i am selecting line by line. So they are showing some 123, 450, 500, 120 for which my program shows 124,451,501,120. Except for the last line, all line.length() shows an increased by 1 value.

推荐答案

$ c> inputFile 有Windows样式的换行符（CRLF），但您的程序正在拆分类似Unix的换行符（LF）上的输入，因为 std :: getline（） ，默认打开 \\\
，留下CR（ \r ）。

It looks like inputFile has Windows-style line-breaks (CRLF) but your program is splitting the input on Unix-like line-breaks (LF), because std::getline(), breaks on \n by default, leaving the CR (\r) at the end of your string.

您需要修剪无关的 \r 。这里有一种方法，以及一个小测试：

You'll need to trim the extraneous \rs. Here is one way to do it, along with a small test:

#include <iostream>
#include <sstream>
#include <iomanip>

void remove_carriage_return(std::string& line)
{
    if (*line.rbegin() == '\r')
    {
        line.erase(line.length() - 1);
    }
}

void find_line_lengths(std::istream& inputFile, std::ostream& output)
{
    std::string currentLine;
    while (std::getline(inputFile, currentLine))
    {
        remove_carriage_return(currentLine);
        output
            << "The current line is "
            << currentLine.length()
            << " characters long and ends with '0x"
            << std::setw(2) << std::setfill('0') << std::hex
            << static_cast<int>(*currentLine.rbegin())
            << "'"
            << std::endl;
    }
}

int main()
{
    std::istringstream test_data(
        "\n"
        "1\n"
        "12\n"
        "123\n"
        "\r\n"
        "1\r\n"
        "12\r\n"
        "123\r\n"
        );

    find_line_lengths(test_data, std::cout);
}

输出：

The current line is 0 characters long and ends with '0x00'
The current line is 1 characters long and ends with '0x31'
The current line is 2 characters long and ends with '0x32'
The current line is 3 characters long and ends with '0x33'
The current line is 0 characters long and ends with '0x00'
The current line is 1 characters long and ends with '0x31'
The current line is 2 characters long and ends with '0x32'
The current line is 3 characters long and ends with '0x33'

注意事项：

• t需要测试EOF。 std :: getline（） 将返回流，当它可以从 inputFile 中不再读取时，将转换为 false / li>
  
• 您不需要复制字符串来确定其长度。

• You don't need to test for EOF. std::getline() will return the stream, which will cast to false when it can read no more from inputFile.
• You don't need to copy a string to determine its length.

这篇关于Getline to String复制换行符的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！