C++: Moving backwards in a file

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I want to move backwards and extract the whole line in which 'new' occurs.

C++

#include <fstream>
#include <iostream>
#include <string>

using namespace std;

int main()
  {
char word[30];
  string filename;
  
  cout << "Name your file> ";
  getline( cin, filename );

  fstream file( filename.c_str() );
  if (!file)
    {
    cout << "I could not open the file. Fooey.\n";
    return EXIT_FAILURE;
    }
  else 
    {
    string line;
    
    while (!file.eof())
      {
          file >> word;
		if(strcmpi(word,"new")==0)		
           {
			/*getline( file, line );
				cout << line;*/
		}

	 
     
      }
    file.close();
    }

  return EXIT_SUCCESS;
  }

Posted 23-Jan-12 23:59pm

Member 8576081

Updated 24-Jan-12 0:12am

Slacker007

v2

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CPallini · Accepted Answer · 2012-01-24T00:20:00

Solution 1

Why don't you read the file line by line (using std::getline[^]), and search the "new" string inside the line? This way (on successful find[^] call) you already have the needed line.

[updated]
Something like this (not tested):

C++

do
{
  getline( file, line);
  if ( ! file.good() ) break; // end of file or some other error
  if ( line.find("new") != string::npos)
  {
    // found: here 'line' is the wanted line.
  }
} while ( true );

[/updated]

Posted 24-Jan-12 0:20am

CPallini

Updated 24-Jan-12 0:37am

v2

Comments

Espen Harlinn 24-Jan-12 6:25am

5'ed!

CPallini 24-Jan-12 6:37am

Thank you.

Shmuel Zang 24-Jan-12 6:28am

5'ed.

CPallini 24-Jan-12 6:37am

Thanks.

Member 8576081 · Accepted Answer · 2012-01-24T00:27:00

Solution 3

@cpallini - thanx a lot for your help.. can you please write in a little code snippet to solve my problem. i am very new to programming.. i tried what you suggested but in vain..thanx again

Posted 24-Jan-12 0:27am

Member 8576081

Member 8576081 · Accepted Answer · 2012-01-24T01:04:00

Solution 4

Thank you so much it worked....Its my first assignment ..taht is why i am getting stuck at stupid things...i am really thankful to you that you took out time for solving my problem ..thanks once again

Posted 24-Jan-12 1:04am

Member 8576081

Member 8576081 · Accepted Answer · 2012-01-24T01:12:00

Solution 5

can you tell me how to identify the pointer variable's name after extracting the lines with 'new' statement.. i am developing a parser to detect memory leaks.
for ex I have
int* p = new int;
i need 'p' to be stored in a map. so as to make sure that it is deleted later on

Posted 24-Jan-12 1:12am

Member 8576081