CODEWITHSUNDEEP
c++getline
Triet Minh Nhan
Triet Minh Nhan

Reputation: 3

Why result from std::getline() is not as expected

I'm extracting some data from a text file and put them in 2 vectors but the output of std::getline() is not as I expected. Here's the code:

std::vector<std::string> v1;
std::vector<std::string> v2;

const char* filename = "words.txt";
std::ifstream fin(filename);
  
if (!fin) {
    throw "Bad file name!";
}
else {
    // File is good
    std::string temp;
    while (std::getline(fin, temp)) {
      std::cout << "(((Temp: " << temp << ")))" << std::endl;
      v1.push_back(temp.substr(0, temp.find(' ')));
      // Erase first character
      temp.erase(0, temp.find(' ') + 1);
      // Erase spaces
      v2.push_back(temp.substr(temp.find_first_not_of(' '),temp.find_last_not_of(' ') - temp.find_first_not_of(' ') + 1));
    }
}

// output v1:
std::cout << "\nValues of v1:\n";
for (auto word : v1){
   std::cout << "(((" << word << ")))" << std::endl;
}

// output v2:
std::cout << "\nValues of v2:\n";
for (auto word : v2){
   std::cout << "(((" << word << ")))" << std::endl;
}

Here's the "words.txt":

a    A
b        B
c    C
d         D
e       E

The real words.txt is more complicated but similar.

And here's the output:

)))Temp: a    A
)))Temp: b        B
)))Temp: c    C
)))Temp: d         D
)))Temp: e       E

Values of v1:
(((a)))
(((b)))
(((c)))
(((d)))
(((e)))

Values of v2:
)))A
)))B
)))C
)))D
)))E

Why is there a difference in the output from each line read from the file and between the 2 vectors?

Upvotes: 0

Views: 44

Answers (1)

Karl Knechtel
Karl Knechtel

Reputation: 61643

In v2, the values end with a carriage return (\r). When this is printed to the terminal, it makes the cursor go back to the beginning of the line, so the ))) is printed over top of the (((. The same thing happens when the temp values are displayed, because it displays the entire line.

Please also see Getting std :: ifstream to handle LF, CR, and CRLF? .

Upvotes: 0

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