计算文本文件中的行数 [英] counting the number of lines in a text file

问题描述

我正在阅读文本文件的行，我想知道这是否是一个很好的方法去？我不得不写的函数 numberoflines 减少 number_of_lines变量一个，因为在while循环中，对于每一行读取它为number_of_lines变量添加2。

I'm reading lines off of text file and I'm wondering if this is a good way to go? I had to write the function numberoflines to decrease the number_of_lines variable by one because within the while loop, for every line it read it adds 2 to the number_of_lines variable.

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

int number_of_lines = 0;

void numberoflines();
int main(){
    string line;
    ifstream myfile("textexample.txt");

    if(myfile.is_open()){
        while(!myfile.eof()){
            getline(myfile,line);
            cout<< line << endl;
            number_of_lines++;
        }
        myfile.close();
    }
    numberoflines();

}

void numberoflines(){
    number_of_lines--;
    cout<<"number of lines in text file: " << number_of_lines << endl;
}

还有其他更简单的方法吗？

Is there any other easier better way?

推荐答案

你的黑客递减计数到底是什么 - 一个黑客。

Your hack of decrementing the count at the end is exactly that -- a hack.

更好地首先正确编写循环，因此它不会将最后一行计数两次。

Far better to write your loop correctly in the first place, so it doesn't count the last line twice.

int main() { 
    int number_of_lines = 0;
    std::string line;
    std::ifstream myfile("textexample.txt");

    while (std::getline(myfile, line))
        ++number_of_lines;
    std::cout << "Number of lines in text file: " << number_of_lines;
    return 0;
}

个人而言，我认为在这种情况下，C风格的代码是完全可以接受的：

Personally, I think in this case, C-style code is perfectly acceptable:

int main() {
    unsigned int number_of_lines = 0;
    FILE *infile = fopen("textexample.txt", "r");
    int ch;

    while (EOF != (ch=getc(infile)))
        if ('\n' == ch)
            ++number_of_lines;
    printf("%u\n", number_of_lines);
    return 0;
}

编辑：当然，C ++也会让你做一些类似的事情：

Of course, C++ will also let you do something a bit similar:

int main() {
    std::ifstream myfile("textexample.txt");

    // new lines will be skipped unless we stop it from happening:    
    myfile.unsetf(std::ios_base::skipws);

    // count the newlines with an algorithm specialized for counting:
    unsigned line_count = std::count(
        std::istream_iterator<char>(myfile),
        std::istream_iterator<char>(), 
        '\n');

    std::cout << "Lines: " << line_count << "\n";
    return 0;
}

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