CODEWITHSUNDEEP
c++filefstream
mahmood
mahmood

Reputation: 24825

Overwritting the content of file on each std::ofstream call

The following code

#include <fstream>
void print( std::ofstream &f, int a ) {
   f << a << '\n';
}

int main () {
   std::ofstream fout( "out.txt" );
   print( fout, 1 );
   print( fout, 2 );
   return 0;
}

produces an output like this

1
2

However I want to see only 2. In other words, I want to overwrite the content of the output file whenever I call the print.

The reason for that, is that I want to call an update function in intervals. As a result, each time the update function is called, the new stats should appear in the output file (not appending the current with previous one).

P.S: putting fout.clear() between the two print calls won't do the job.

Upvotes: 0

Views: 137

Answers (1)

πάντα ῥεῖ
πάντα ῥεῖ

Reputation: 1

Simply use the std::ofstream::seekp() to reset the output position between the print() calls

   std::ofstream fout( "out.txt" );
   print( fout, 1 );
   fout.seekp(0); // <<<<
   print( fout, 2 );

Note that fout.clear() just resets the error states of the stream.

Upvotes: 2

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