Thread: Ignoring line in C++ when reading from file

Hi all!

I have the following codes i use to read from a textfile.

Code:

while(!textfile.eof())
  { //textfile is a ifstream                      
     textfile >> string1 >> string2;
     //use strings for processing
   }

however my above program hits an error when there is a blank line in the text file. i would only want to process the information if only the link is not blank. i have tried a couple of ways but they couldnt work.. is there anyway for me to check if the line is blank using the ifstream textfile that i got? and only if the line is not blank can i go process the data.

Thanks in advance

That code should skip blank lines correctly. Can you post a more complete example that demonstrates the problem?

BTW, using eof() to control the loop that way is a bad idea. It will often lead to processing of the last line twice. NOrmally you would use this:

Code:

while(textfile >> string1 >> string2)
  { //textfile is a ifstream                      
     //use strings for processing
   }

operator >> will skip over all whitespace, including multiple newlines, so you really shouldn't have to switch to getline. Of course, if you want to read in strings with embedded spaces, then you do want to switch.

Hi this is my code that got error when encounter blank lines.

Code:

while(!textFile.eof())
  {                                                           
        if(line == 0)
         {                  
           textFile >> string1 >> string2;
         }
        else if(line == 1)
         {
            textFile >> string1 >> string2 >> string3;
          }   
        else
        {
            //no action   
         }     
        line++;
}

Anything wrong with above? why did i get error when the datafile got a blank line?

Code:

while(!textFile.eof())

Is usually a bad thing, but in this case, it may succeed. Suggest you read the FAQ about that and beware using it.

What does your input file look like?