What is getline() method in C\C++?

Overview

The getline() function is used in C++ to read a string from the input. It helps to retrieve characters from the input.

Syntax

istream& getline(isstream& fin, string& str, char delim);

Parameters

Let’s discuss the parameters of the function:

  • fin: An object of istream class used to send a command to function about reading the input from the stream.
  • str: A string object to store input.
  • delim: A delimitation character used to stop function after reaching the target character.

Example

Let’s look at the code below:

main.cpp
data.txt
#include <iostream>
#include <fstream>
#include <string>
int main() {
 std::string fname, lname, nationality;
  // ifstream instance
  std::ifstream fin;
  // opening a file named data.txt
  fin.open("data.txt");
  if (fin.is_open()) {
    // extract first name 
    std::getline(fin, fname);
    // extract last name from file
    std::getline(fin, lname);
    // extract nationality or country
    std::getline(fin, nationality);
    // closing opend file
    fin.close();
    // print data on console
    std:: cout << "\n-----Entered details-----\n" << '\n';
    std::cout << "Name: " << fname << std::endl;
    std::cout << "Father Name: " << lname << std::endl;
    std::cout << "Nationality: " << nationality << std::endl;
  } else {
    std::cout << "Unable to open file.";
  }
}

Explanation

Here is a line-by-line explanation of the above code:

main.cpp

  • Line 8: We create ifstream an instance to read from a file.
  • Lines 10 to 11: We load a file named data.txt and validate it. And use fin.is_open() function to check whether the specified file is loaded or not.
  • Lines 13, 15 and 17: We invoke std::getline() method to extract first name (fname), last name (lname), and nationality from the loaded file.
  • Line 19: We close the opened file using fin.close().
  • Lines 22 to 24: We print data to the console.

data.txt

  • Line 1: It contains the first name.
  • Line 2: It contains the last name or father name.
  • Line 3: It contains the nationality of person.

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