C++按行读取文本文件，并将每行字符串拆分为double value的坐标值

目的：按行读取coordinates.txt文件中的字符串，并将该字符串拆分成double类型的点坐标值。

“coordinates.txt”内容如下：

0.61028 0.45567 0.51456 0.59547 0.4640 0.52091 0.58599 0.4961 0.52521 0.57121 0.52022 0.52475 0.5502 0.53852 0.51548

0.54555 0.50853 0.47956 0.54548 0.5103 0.45003 0.54248 0.5078 0.42583 0.53301 0.50517 0.39883 0.5196 0.50449 0.51026

“main.cpp”如下：

#include <iostream>
#include <sstream>
#include <fstream>
#include <string>
#include "stdlib.h"

int main(int argc, char *argv[]){

if (argc < 2) {
std::cout << "Usage: " << argv[0] << "filename" << std::endl << std::endl;
return -1;
}

// define the file to be read
std::ifstream fin(argv[1], std::ios::in);
// set the buffer size
char line[1024] = {0};

int i = 1;
// read each line
while(fin.getline(line, sizeof(line))){
// set the current line to a stringstream
std::stringstream ss(line);

// split the current line into double values
std::cout<<"The points in the "<<i<<"th line are: "<<std::endl;
while (!ss.eof()) {
double p[3];
std::string token;
for(unsigned dim = 0; dim < 3; dim++){
ss >> token;
p[dim] = atof(token.c_str());
}
std::cout << "<" << p[0] << " " << p[1] << " " << p[2] << ">" << std::endl;
}
std::cout<<std::endl;
i++;
}

fin.close();

return 0;
}

编译：

$ g++ main.cpp -o main

运行：

$ ./main ./test/coordinates.txt

结果：