How to use getline() in C++ when there are blank lines in input?

Last Updated : 03 Jun, 2022

In C++, if we need to read a few sentences from a stream, the generally preferred way is to use the getline() function as it can read string streams till it encounters a newline or sees a delimiter provided by the user. Also, it uses <string.h> header file to be fully functional.

Here is a sample program in c++ that reads four sentences and displays them with ": newline" at the end

CPP

// A simple C++ program to show working of getline #include <cstring> #include <iostream> using namespace std; int main() {     string str;     int t = 4;     while (t--) {         // Read a line from standard input in str         getline(cin, str);         cout << str << " : newline" << endl;     }     return 0; }

Sample Input :

 This  is  Geeks  for

As the expected output is:

This : newline is  : newline Geeks : newline for : newline

The above input and output look good, there may be problems when the input has blank lines in between.

Sample Input :

This  is   Geeks  for

Output:

This : newline  : newline is  : newline  : newline

It doesn't print the last 3 lines. The reason is that getline() reads till enter is encountered even if no characters are read. So even if there is nothing in the third line, getline() considers it as a single line. Further, observe the problem in the second line. The code can be modified to exclude such blank lines. Modified code:

CPP

// A simple C++ program that uses getline to read // input with blank lines #include <cstring> #include <iostream> using namespace std; int main() {     string str;     int t = 4;     while (t--) {         getline(cin, str);          // Keep reading a new line while there is         // a blank line         while (str.length() == 0)             getline(cin, str);          cout << str << " : newline" << endl;     }     return 0; }

Input:

This  is   Geeks  for

Output:

This : newline is  : newline Geeks : newline for : newline

How to Take Input in Array in C++?

Sarin Nanda

Improve

Article Tags :

Practice Tags :

Similar Reads

How to Take Input in Array in C++?

Arrays in C++ are derived data types that can contain multiple elements of the same data type. They are generally used when we want to store multiple elements of a particular data type under the same name. We can access different array elements using their index as they are stored sequentially in th

3 min read

How to Read and Print an Integer value in C++

The given task is to take an integer as input from the user and print that integer in C++ language. In this article, we will learn how to read and print an integer value. In the below program, the syntax and procedures to take the integer as input from the user is shown in C++ language. Standard Inp

2 min read

Reading Lines by Lines From a File to a Vector in C++ STL

Prerequisites: STL in C++Vector in C++File handling in C++ The Standard Template Library (STL) is a set of C++ template classes to provide common programming data structures and functions such as lists, stacks, arrays, etc. It is a library of container classes, algorithms, and iterators. Vector in C

2 min read

How to split a string in C/C++, Python and Java?

Splitting a string by some delimiter is a very common task. For example, we have a comma-separated list of items from a file and we want individual items in an array. Almost all programming languages, provide a function split a string by some delimiter. In C: // Splits str[] according to given delim

7 min read

Find sum of integers in a file which contains any characters

You are given a text file which contains any type of characters. You have to find the sum of integer values. Examples: Input : text.txt Let contents of test.txt be : :-,,$%^5313&^*1)(*( 464sz29>>///11!!! (*HB%$#)(*0900 Output : 6727 Input : text1.txt Let contents of test.txt be : 234***3r3

2 min read

lseek() in C/C++ to read the alternate nth byte and write it in another file

From a given file (e.g. input.txt) read the alternate nth byte and write it on another file with the help of â€œlseekâ€. lseek (C System Call): lseek is a system call that is used to change the location of the read/write pointer of a file descriptor. The location can be set either in absolute or relati

2 min read

std::basic_istream::getline in C++ with Examples

The std::basic_istream::getline is used to extract the characters from stream until end of line or the extracted character is the delimiting character. The delimiting character is the new line character i.e '\n'. This function will also stop extracting characters if the end-of-file is reached if inp

2 min read

Set Position with seekg() in C++ File Handling

seekg() is a function in the iostream library that allows you to seek an arbitrary position in a file. It is included in the <fstream> header file and is defined for istream class. It is used in file handling to sets the position of the next character to be extracted from the input stream from

3 min read

How to write long strings in Multi-lines C/C++?

Image a situation where we want to use or print a long long string in C or C++, how to do this? In C/C++, we can break a string at any point in the middle using two double quotes in the middle. Below is a simple example to demonstrate the same. C/C++ Code #include<stdio.h> int main() { // We c

2 min read

list::front() and list::back() in C++ STL

Lists are containers used in C++ to store data in a non-contiguous fashion, Normally, Arrays and Vectors are contiguous in nature, therefore the insertion and deletion operations are costlier as compared to the insertion and deletion option in Lists. list::front() This function is used to reference

3 min read