Question

I am writing a binary file in C++, where I traverse to a particular location and need to over-write the contents with the new one. I know the contents of the integer size, so I keep track of the location and over write it. Seems like, ofstream write function inserts or appends the variable. Is there a way, where I can over write, instead of appending or inserting in a file

  long word = sizeof(int) + sizeof(long) + sizeof(long);

 std::ofstream file_write(filename, std::ios::out|std::ios::binary);

 file_write.seekp(word);      
 long pos = file_write.tellp();
 file_write.write((char *)&some_integer,sizeof(int));
 file_write.close()

 //some other location

 file_write.seekp(pos);
 file_write.write((char *)&some_other_integer,sizeof(int));

//Here some_integer should be over written by some_other_integer. Is there a way to do it?

That will be like

value1,value2,value3

I might be able to replace value 2 with value 5.

then it should look like

value1,value5,value3

Answer 1

You need to add std::ios::trunc to your open parameters, as in:

std::ofstream file_write(filename, std::ios::out|std::ios::binary|std::ios::trunc);

That will truncate the file, discarding any existing content.