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,
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
/*
* 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.
// 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.
std::vector<std::string>
Now Data of each row i.e. vector<string> will be stored in another vector i.e.
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.
/*
* 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.
// 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,
#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:
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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