Problem with combining lines form file with custom text in cout

Question

I have problem with combining strings from getline with other ones in cout, i have been searching answers but I couldn't find anyone who had similiar problems. My code is:

file.open ("list.txt");
    getline(file, line);
    int i=0;
    do
    {
        getline(file, line);
        dummyStudent.name = line;
        cout << "Is " << flush << dummyStudent.name << flush << " present?" << endl;
        students.push_back(dummyStudent);
        i++;
    }
    while(!file.eof());
    file.close();

The output should be:

Is student present?

But instead i get:

 present?udent

and the last iteration of loop shows correct text.

I believe this is your problem - https://stackoverflow.com/questions/2129230/cout-order-of-call-to-functions-it-prints — Kai, Dec 10 '19 at 20:48
@Kai doesn't look like it. Everything in that `cout` statement is independent of each other, so there's shouldn't be UB because of sequence points here. — scohe001, Dec 10 '19 at 20:51
Maybe its due to carriage return (`\r`) at the end of each line except the last? — n314159, Dec 10 '19 at 20:52
Can you check the result of `getline` to see if it's `false`? — AndyG, Dec 10 '19 at 21:02

scohe001 · Answer 1 · 2019-12-10T21:10:13.673

4

Let me take a guess here. Your file was created or edited on Windows, but you're not using Windows to build/run your code. So instead of newline characters at the end of each line (\n) you have newlines and carriage returns: \r\n. However there's no newline (and so no carriage return) on the very last line of the file--so only that one looks good. Am I right?

A carriage return will return the cursor to the beginning of the line. So you read in student\r and then std::cout writes Is student, sees the carriage return and moves the cursor back to the beginning of the line and writes present? there. Resulting in present?udent.

Either strip the whitespace from the end of your name string (with the help of code from https://stackoverflow.com/a/217605/2602718)

static inline void rtrim(std::string &s) {
    s.erase(std::find_if(s.rbegin(), s.rend(), [](int ch) {
        return !std::isspace(ch);
    }).base(), s.end());
}

int main() {
    //...
    getline(file, line);
    dummyStudent.name = line;
    rtrim(dummyStudent.name);
    cout << "Is " << flush << dummyStudent.name << flush << " present?" << endl;
    //...

Or remove those characters from your file. (After hearing that you're on MacOS, you could remove those characters from the file with something like this: Removing Carriage return on Mac OS X using sed)

edited Dec 10 '19 at 21:10

answered Dec 10 '19 at 20:56

scohe001

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shouldn't be a problem on windows with the file opened in text mode. should only be a problem in binary mode or reading windows files on other platforms – Alan Birtles Dec 10 '19 at 21:00
I guess I just assumed they were on Linux @Alan. I've edited to make explicit the assumption that they're not building/running on Windows. Good catch! – scohe001 Dec 10 '19 at 21:02
The question is tagged visual-c++ so I assume they are on windows. Stray carriage returns is definitely the issue though – Alan Birtles Dec 10 '19 at 21:04
my file was eddited on windows but I'm on a mac – Bruno M Dec 10 '19 at 21:05
@Bruno in that case I'd look at running something like this on your file: https://stackoverflow.com/q/21621722/2602718 – scohe001 Dec 10 '19 at 21:06
I'll try thank you – Bruno M Dec 10 '19 at 21:10

Problem with combining lines form file with custom text in cout

1 Answers1