C++: ctrl+d terminates program (ubuntu)

Question

(New to C++)

I have this simple code (simplified for the question):

 int main()
{
    string currInput;
    while (getline(cin, currInput))
    {
    }
    cout << "wont be printed" << std::flush;
    return 0;
}

I have been debugging for a while and I probably miss something:

When running it and pressing ctrl+d (after some strings or right away), it does not print the string that is after the while loop. It just stop running. I thought it might be something with flushing so I added that too. What am I missing?

PS: When running in debug, it mentions something about sighup signal.

_"it mention something about sighup signal"_ You probably want to add code to ignore the [`SIGHUP`](https://stackoverflow.com/questions/18551485/how-to-make-the-process-ignore-some-signallike-sighup-sigabrt-sigabort-sigint-e) signal. — user0042, Aug 29 '17 at 21:21
We haven't learned about signals yet, and I couldnt fine any example that handles this, do you have any reference? — Kobi T, Aug 29 '17 at 21:23
Check the link from my comment. It leads to a number of references in the answer and the comments. — user0042, Aug 29 '17 at 21:27
oops wait, missed the "start the program" part, how do you want me to compile it? — Kobi T, Aug 29 '17 at 21:53
It seems to be working this way! It's all cLion's fault? Is there a way to change it's behavior? can you try it on your machine with cLion (if you have it installed)? — Kobi T, Aug 29 '17 at 22:01
The cLion console is not very reliable, apparently. (I've never used it but I've seen lots of problems reported here.) — rici, Aug 29 '17 at 22:08
Possible duplicate of [sending EOF to stdin in Clion IDE](https://stackoverflow.com/questions/36405577/sending-eof-to-stdin-in-clion-ide) — scohe001, Aug 29 '17 at 23:57

Kobi T · Accepted Answer · 2017-08-29T22:19:36.823

1

So, with a lot of help from @manni and @rici, we found the problem.

It turns out to be a known problem in cLion.

see sending EOF to stdin in Clion IDE

https://intellij-support.jetbrains.com/hc/en-us/community/posts/206849765-How-to-enter-EOF-Ctrl-z-in-Run-console-

https://youtrack.jetbrains.com/issue/IDEA-12514

edited Aug 29 '17 at 22:19

answered Aug 29 '17 at 22:10

Kobi T

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score -2 · Answer 2 · edited Feb 21 '20 at 10:44

-2

Your error is the while loop. You should not be using a loop here. What happens is it hits this line and attempts to get input. Regardless of whether you type in anything or not, if you hit CTRL+D it will end the getline. But you have it in a while loop....so it'll hop back to the top of the loop and get another line...then another line....then another line. Welcome to your first infinite loop.

while (getline(cin, currInput))
{
}

The simplest thing would be to do just

getline(cin, currInput);

If you're starting out programming this is probably what you want to do anyway.

If you feel gutsy, read this page: http://www.cplusplus.com/reference/string/string/getline/

You'll notice that getline returns the stream you pass in. Which will evaluate to true as far the loop is concerned.

edited Feb 21 '20 at 10:44

Werner Henze

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answered Aug 29 '17 at 21:29

Jerry Saravia

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First of all, thanks for your comment. I know that's not the right way to write this code, I wanted to simplify a more complex code for the question. It doesn't enter an infinite loop, it exits and return 0 without printing the last line. – Kobi T Aug 29 '17 at 21:35
oh, lol. You said "(New to C++)" so I imagined you were brand spanking new. – Jerry Saravia Aug 29 '17 at 21:37
@KobiT If that's the case, then the SIGHUP link is a good way to go. Understand how to handle the signal. – Jerry Saravia Aug 29 '17 at 21:39
how does this code work without handling it: https://stackoverflow.com/questions/20756968/reading-multiple-lines-from-a-file-using-getline In which cases should I handle it? I've seen many examples of while loop with getline and none of them mentioned it. – Kobi T Aug 29 '17 at 21:41
http://en.cppreference.com/w/cpp/io/basic_ios/operator_bool explains how functions which return an `istream` are *designed* to work with conditionals and `while` statements. – rici Aug 29 '17 at 21:43
Thanks, @rici. My interpretation of the istream return from the `getline` call is wrong. It should be obvious by now I don't do C++ often. – Jerry Saravia Aug 29 '17 at 21:51
Jerry, since OP's code actually works (in a terminal), you might want to consider editting your answer. – rici Aug 29 '17 at 22:11

C++: ctrl+d terminates program (ubuntu)

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