2

I am learning C++. I want to take multiple line string as input but I can't. I am using getline() for it but it is taking only one line input. When I press enter for writing next line it stoped taking input and print the first line.

I want to give input like the example below

Hello, I am Satyajit Roy.
I want to make a program.
I love to travel.

But it takes only the first line input.

My code:

#include <iostream>
#include <string>
using namespace std;

int main()
{
    string s;
    getline(cin, s);
    cout << s << endl;

    return 0;
}

Please help me to know how can I do that. Thank you.

Improve this question
8
  • 1
    How about while (getline(cin, s)) cout << s << endl;? Commented Sep 10, 2020 at 17:45
  • Do you really have one empty line inbetween at your input? Commented Sep 10, 2020 at 17:46
  • 1
    getline optionally takes a delimiter as parameter. How do you know when input is finished? Is it always 3 lines? Commented Sep 10, 2020 at 17:46
  • πάντα ῥεῖ No sir, there is no empty line inbetween input. Commented Sep 10, 2020 at 17:48
  • @idclev463035818 "How do you know when input is finished?" Well, for std::cin it's CTRL-Z (CTRL-D respectively), for file based input it's EOF, no? Commented Sep 10, 2020 at 17:49

3 Answers 3

Reset to default
3

Either you write a loop to read individual lines and concatenate them to a single string, thats what this answer suggests. If you are fine with designating a specific character to signal the end of the input, you can use the getline overload that takes a delimiter as parameter:

#include <iostream>
#include <string>


int main() {
    std::string s;
    std::getline(std::cin,s,'x');
    std::cout << s;
}

The user would have to type an x to end input, so this input

Hello, I am Satyajit Roy.
I want to make a program.
I love to travel.
x

would result in this output:

Hello, I am Satyajit Roy.
I want to make a program.
I love to travel.

Of course this won't work when the string to be entered contains x, which renders the approach rather useless.

However, instead of using a "real" character as delimiter you can use the EOF character (EOF = end of file) like this:

 std::getline(std::cin, s, static_cast<char>(EOF));

Then input is terminated by whatever your terminal interprets as EOF, eg Ctrl-d in linux.

Thanks to @darcamo for enlightening me on the EOF part.

Improve this answer
Sign up to request clarification or add additional context in comments.

1 Comment

You can use the "end of file" as the designated character with std::getline(std::cin, s, static_cast<char>(EOF)); EOF is an integer type, usually defined as -1. That is why you need the cast. With that, you can type your multiline string and use whatever key combination your terminal uses for the EOF character when you want to finish entering the string. For instance, you can write your multiline string, type ENTER to create an empty line and then type Ctrl+d to enter the EOF character (works in Linux). Everything before the last empty line will be captured by std::getline
1

You can only read one line at a time with std::getline if you don’t provide your own delimiter. If you want to accumulate multiple lines, one at a time, you need a place to put the result. Define a second string. Read a line at a time into s with std::getline, and then append s to the result string. Like this:

std::string result;
std::string s;
while (std::getline(std::cin, s))
    result += s;
Improve this answer

1 Comment

@idclev463035818 — yes, I said it too strongly. Thanks.
1

You can take several lines using the code below if you know how many lines you will input.

int line=3, t;
string s, bigString;

for(int i=0 ; i<line ; i++)
{
    getline(cin,s); // This is to input the sentence
    bigString += s + "\n";
}

cout << bigString;

If you don't know how many lines you will input (Input from file until end of file) then you can check this.

string s;
vector<string> all;

while(getline(cin,s))
{
     all.push_back(s);// This is to input the sentence

}

for(auto i:all)
{
    cout << i << endl;
}
Improve this answer

Comments

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.