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Counting lines in a text file and further operations

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Join Date: Apr 2007

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roflol

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Counting lines in a text file and further operations

Aug 16th, 2007

So I'm trying to count the number of lines in a text file. I think I got it working, but it seems I can't do further correct processing on the text file, maybe because getline extracts the data? The operations I want to perform include inputting values read from the file into an array (This works correctly if I comment out the code for counting the lines, but the output is wrong if I include the code).

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 C++ Syntax (Toggle Plain Text) 
 
   string fileName;
   cin >> fileName;
   ifstream inData;
 
   inData.open( fileName.c_str() );
   if ( !inData ) 
      return 0;
 
   size = 0;
   string line;
   while ( !inData.eof() )
   {
       getline(inData, line);
       size++;
   }
 
   string fileName;
   cin >> fileName;
   ifstream inData;
   
   inData.open( fileName.c_str() );
   if ( !inData ) 
      return 0;
   
   size = 0;
   string line;
   while ( !inData.eof() )
   {
       getline(inData, line);
       size++;
   }

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Join Date: Aug 2005

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Ancient Dragon Ancient Dragon is offline

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Re: Counting lines in a text file and further operations

Aug 16th, 2007

that's because the loop is wrong. You don't need to use eof() at all

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 C++ Syntax (Toggle Plain Text) 
while( getline(inData, line) )
{
    size++;
    // do other stuff here
}
while( getline(inData, line) )
{
    size++;
    // do other stuff here
}

Last edited by Ancient Dragon; Aug 16th, 2007 at 9:44 am.

Don't PM me with questions -- you might get a nasty PM in response. If you have a question then post it in one of the forums.

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Join Date: Apr 2007

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roflol

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Re: Counting lines in a text file and further operations

Aug 16th, 2007

There's still a problem : /, I need the number of lines before I can correctly do the other stuff.

Last edited by roflol; Aug 16th, 2007 at 10:28 am.

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Join Date: Apr 2007

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roflol

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Re: Counting lines in a text file and further operations

Aug 16th, 2007

Did some reading, I got it working I think. I just had to add:

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inData.clear();
inData.close();
inData.open( fileName.c_str() );
inData.clear();
inData.close();
inData.open( fileName.c_str() );

to clear the stream and read from the beginning of the file again.

Thanks for the help.

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Join Date: Dec 2006

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vijayan121 vijayan121 is offline

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Re: Counting lines in a text file and further operations

Aug 16th, 2007

you do not have to close and then reopen the file; inData.clear() ; inData.seekg(0) ; is more efficient.
> I need the number of lines before I can correctly do the other stuff.
you do not; use a vector instead of a c-style array:

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
#include <iostream>
#include <fstream>
#include <string>
#include <vector>
using namespace std ;
 
int main()
{
   ifstream file( __FILE__ ) ;
   string line ;
   vector<string> lines ;
   while( getline( file, line ) ) lines.push_back( line ) ;
   cout << "#lines: " << lines.size() << '\n' ;
}
#include <iostream>
#include <fstream>
#include <string>
#include <vector>
using namespace std ;

int main()
{
   ifstream file( __FILE__ ) ;
   string line ;
   vector<string> lines ;
   while( getline( file, line ) ) lines.push_back( line ) ;
   cout << "#lines: " << lines.size() << '\n' ;
}