CODEWITHSUNDEEP
c++stringifstreamgetline
recoba78
recoba78

Reputation: 99

How to test if a line is empty?

I'm actually trying to understand how does the getline() function works! But I'm facing difficulties to test if a line is empty or not!

Here is my code:

ifstream fichier("upload.txt",ios::binary);
string ligne;
while(getline(fichier,ligne))
{
    cout<<ligne<<endl;
    if(ligne=="")
         cout<<"line below is empty"<<endl;         
}

But, the if-condition seems to be not working :((

Upvotes: 0

Views: 293

Answers (2)

Remy Lebeau
Remy Lebeau

Reputation: 598384

On Windows, a line break is normally CRLF (0x0D 0x0A). std::getline() will read until it encounters the LF and discard it from the returned std::string. If the std::ifstream is opened in text mode (the default mode), platform line breaks are normalized to LF and a leading CR will also be discarded. But, if opened in binary mode, the CR will not be discarded. So you will have to check for that:

ifstream fichier("upload.txt", ios::binary);
string ligne;
while (getline(fichier, ligne)) {
    if (ligne.empty() || ligne == "\r") {
        cout << "line is empty" << endl;
    } else {
        cout << ligne << endl;
    }
}

Otherwise, don't use binary mode for text files:

ifstream fichier("upload.txt");
string ligne;
while (getline(fichier, ligne)) {
    if (ligne.empty()) {
        cout << "line is empty" << endl;
    } else {
        cout << ligne << endl;
    }
}

Upvotes: 2

H S
H S

Reputation: 1221

Your problem is opening file in binary. Other than that, you should do few things :

  1. Check if file is properly opened
  2. Compare against empty()
  3. Check if string only contains space , then it's considered empty.

  4. Close file

    ifstream fichier("upload.txt", std::ifstream::in ); //File opened for reading.
string ligne;
//Always Check if file is properly opened.
if (fichier.is_open() ) 
{
   while(getline(fichier,ligne))
   {
      cout<<ligne<<endl;
       if(ligne.empty() || str.find_first_not_of(' ') == std::string::npos)
        cout<<"line below is empty"<<endl;         
   }
   fichier.close();

}
else 
{
 // show message:
  std::cout << "Error opening file";
}

Upvotes: 0

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