How to read data from a csv file in C++ ?
In this article we will discuss and create a class to read data from a CSV File.
What is a CSV File ?
A csv file is a kind of flat file used to store the data. In this each row contains data separated by comma.
For example,
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20,hi,99 3,4,5 a,b,c 3,4,1 |
Creating a Class CSVReader to read Data from CSV File
Let’s create a class CSVReader that provides API to read data from a CSV File
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/* * A class to read data from a csv file. */ class CSVReader { std::string fileName; std::string delimeter; public: CSVReader(std::string filename, std::string delm = ",") : fileName(filename), delimeter(delm) { } // Function to fetch data from a CSV File std::vector<std::vector<std::string> > getData(); }; |
It accepts the filename as constructor argument and provides a member function that reads the content of CSV file and returns the data in a vector of vector<std::string> i.e.
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// Function to fetch data from a CSV File std::vector<std::vector<std::string> > getData(); |
All comma separated elements in a single row will be stored in vector of strings i.e.
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std::vector<std::string> |
Now Data of each row i.e. vector<string> will be stored in another vector i.e.
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std::vector<std::vector<std::string> > |
This member function will parse the content of csv file line by line and store data in vector< vector <string> > i.e.
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/* * Parses through csv file line by line and returns the data * in vector of vector of strings. */ std::vector<std::vector<std::string> > CSVReader::getData() { std::ifstream file(fileName); std::vector<std::vector<std::string> > dataList; std::string line = ""; // Iterate through each line and split the content using delimeter while (getline(file, line)) { std::vector<std::string> vec; boost::algorithm::split(vec, line, boost::is_any_of(delimeter)); dataList.push_back(vec); } // Close the File file.close(); return dataList; } |
Let’s create an object of class CSVReader class and read the data from csv file i.e.
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// Creating an object of CSVWriter CSVReader reader("example.csv"); // Get the data from CSV File std::vector<std::vector<std::string> > dataList = reader.getData(); |
Complete example is as follows,
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#include <iostream> #include <fstream> #include <vector> #include <iterator> #include <string> #include <algorithm> #include <boost/algorithm/string.hpp> /* * A class to read data from a csv file. */ class CSVReader { std::string fileName; std::string delimeter; public: CSVReader(std::string filename, std::string delm = ",") : fileName(filename), delimeter(delm) { } // Function to fetch data from a CSV File std::vector<std::vector<std::string> > getData(); }; /* * Parses through csv file line by line and returns the data * in vector of vector of strings. */ std::vector<std::vector<std::string> > CSVReader::getData() { std::ifstream file(fileName); std::vector<std::vector<std::string> > dataList; std::string line = ""; // Iterate through each line and split the content using delimeter while (getline(file, line)) { std::vector<std::string> vec; boost::algorithm::split(vec, line, boost::is_any_of(delimeter)); dataList.push_back(vec); } // Close the File file.close(); return dataList; } int main() { // Creating an object of CSVWriter CSVReader reader("example.csv"); // Get the data from CSV File std::vector<std::vector<std::string> > dataList = reader.getData(); // Print the content of row by row on screen for(std::vector<std::string> vec : dataList) { for(std::string data : vec) { std::cout<<data << " , "; } std::cout<<std::endl; } return 0; } |
Output:
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20 , hi , 99 , 3 , 4 , 5 , a , b , c , 3 , 4 , 1 , |
To Compile the above code use following command in Linux,
g++ –std=c++11 example.cpp
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