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Aug 16th, 2007

Counting lines in a text file and further operations

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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).

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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roflol

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Aug 16th, 2007

Re: Counting lines in a text file and further operations

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

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.

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Aug 16th, 2007

Re: Counting lines in a text file and further operations

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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Aug 16th, 2007

Re: Counting lines in a text file and further operations

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

C++ Syntax (Toggle Plain Text)
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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Aug 16th, 2007

Re: Counting lines in a text file and further operations

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:

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' ;
}

Last edited by vijayan121; Aug 16th, 2007 at 2:09 pm.

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