Introduction to C++ | getline()

C++ getline()

The getline() function in C++ is used to read a line of text from an input stream. It allows you to read an entire line, including spaces, until the newline character is encountered. This function is typically used when you want to read a complete line of input from the user or from a file.

What is getline()?

getline() is a function provided by the C++ Standard Library in the iostream header. Unlike cin, which stops reading at the first whitespace character, getline() reads input until it encounters the newline character, allowing the input to include spaces.

Syntax of getline()

        #include <iostream>
        #include <string>
        
        getline(input_stream, string_variable);
                    

Function Parameters

• input_stream: The input stream from which data is read (typically cin or if reading from a file, an ifstream object).
• string_variable: A string variable that will hold the input data (the line of text).

Example of Using getline() to Read from Console

Here’s an example of how to use getline() to read a line of text entered by the user:

        #include <iostream>
        #include <string>
        
        using namespace std;
        
        int main() {
            string name;
            
            // Ask for user's name and store it in 'name' variable
            cout << "Enter your name: ";
            getline(cin, name);
            
            // Display the entered name
            cout << "Hello, " << name << "!" << endl;
            
            return 0;
        }
                    

Output

Reading Multiple Lines with getline()

You can use getline() in a loop to read multiple lines of text, one at a time. This is useful when reading data from a file or continuously reading input from the user.

        #include <iostream>
        #include <string>
        
        using namespace std;
        
        int main() {
            string line;
            int lineCount = 1;
        
            // Read 3 lines of input
            while (lineCount <= 3) {
                cout << "Enter line " << lineCount << ": ";
                getline(cin, line);
                cout << "You entered: " << line << endl;
                lineCount++;
            }
        
            return 0;
        }
                    

Output

Using getline() with Files

getline() can also be used to read lines from a file. Here’s an example of how to use it to read a text file:

        #include <iostream>
        #include <fstream>
        #include <string>
        
        using namespace std;
        
        int main() {
            string line;
            ifstream inputFile("example.txt"); // Open file for reading
        
            if (inputFile.is_open()) {
                // Read file line by line
                while (getline(inputFile, line)) {
                    cout << line << endl;
                }
                inputFile.close(); // Close the file after reading
            } else {
                cout << "Unable to open file" << endl;
            }
        
            return 0;
        }
                    

Output

Common Pitfalls

• Ignoring Newline Characters: After using cin to get input, a newline character might still be left in the input buffer. If you follow cin with getline(), it may immediately consume the leftover newline character. This can be avoided by using cin.ignore() before calling getline().
• Input Buffer Issues: If you're reading input after using getline(), ensure that no residual input remains in the buffer.

Pro Tip: