从文件读取C ++放三个怪异的字符 [英] C++ reading from file puts three weird characters

问题描述

当我通过字符串从文件字符串中读取时，>>操作获取第一个字符串，但是它以i开头。假设第一个字符串是街道，比起istreet。

其他字符串都可以。我尝试了不同的txt文件。结果是一样的。第一个字符串以我开始。问题是什么？

这是我的代码：

 ＃包括< iostream> 
 #include< fstream> 
 #include< string> 
 #include< vector> 
使用namespace std; 
 
 int立方体（int x）{return（x * x * x）;} 
 
 int main（）{
 $ b $ int maxChar; 
 int lineLength = 0; 
 int cost = 0; 
 
 cout<<输入每行最大字符数...; 
 cin>> maxChar; 
 cout< endl<<每行的最大字符数是：<<< maxChar<< endl; 
 
 fstream inFile（bla.txt，ios :: in）; 
 
 if（！inFile）{
 cerr<< 无法打开文件datafile.txt; 
 exit（1）; （！inFile.eof（））{
字符串单词; //调用系统停止
} 
 
 
 
 inFile>>字; 
 cout<<单词<< endl; 
 cout<<< word.length（）<< endl; （word.length（）+ lineLength< = maxChar）{
 lineLength + =（word.length（）+1）; 
} 
 else {
 cost + = cube（maxChar-（lineLength-1））; 
 lineLength =（word.length（）+ 1）; 
 
 
 
 
 $ b $ div class =h2_lin>解决方法

您看到一个UTF-8 字节顺序标记（BOM）。它是由创建该文件的应用程序添加的。





要检测并忽略标记，您可以尝试这个（未测试）函数：


$ b $ Skip $




$ char test [4] = {0};
in.read（test，3）;
if（strcmp（test，\xEF\xBB\xBF）== 0）
return true;
in.seekg（0）;
返回false;
}


When i read from a file string by string, >> operation gets first string but it starts with "i" . Assume that first string is "street", than it gets as "istreet".

Other strings are okay. I tried for different txt files. The result is same. First string starts with "i". What is the problem?

Here is my code :

#include <iostream>
#include <fstream>
#include <string>
#include <vector>
using namespace std;

int cube(int x){ return (x*x*x);}

int main(){

int maxChar;
int lineLength=0;
int cost=0;

cout<<"Enter the max char per line... : ";
cin>>maxChar;
cout<<endl<<"Max char per line is : "<<maxChar<<endl;

fstream inFile("bla.txt",ios::in);

if (!inFile) {
    cerr << "Unable to open file datafile.txt";
    exit(1);   // call system to stop
}

while(!inFile.eof()) {
    string word;

    inFile >> word;
    cout<<word<<endl;
    cout<<word.length()<<endl;
    if(word.length()+lineLength<=maxChar){
        lineLength +=(word.length()+1);
    }
    else {
        cost+=cube(maxChar-(lineLength-1));
        lineLength=(word.length()+1);
    }   
}

}

解决方案

You're seeing a UTF-8 Byte Order Mark (BOM). It was added by the application that created the file.

To detect and ignore the marker you could try this (untested) function:

bool SkipBOM(std::istream & in)
{
    char test[4] = {0};
    in.read(test, 3);
    if (strcmp(test, "\xEF\xBB\xBF") == 0)
        return true;
    in.seekg(0);
    return false;
}

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