Thread: fstream

im quite confident reading and writing to files but i was wandering how it would be possible to lift records from one file and put it into another file

for example two text files and i want to copy a character or string from file one and put it into file 2

>> for example two text files and i want to copy a character or string from file one and put it into file 2

uhm. would it not follow some logic similar to

open fileA
open fileB
read stringX from fileA
write stringX to fileB
close fileA and fileB

or is it more complicated..

yeah i got the psuedo...im just struggling with the actual program

You can't simply pick up a piece of data from one file and insert it in another. The logic required is similar to what xhi described.

Open fileA
Read in data from fileA
Extract the data you want copied.
Close fileA
Open fileB
Read in data from fileB
Modify the data how you want in memory (including adding a string from fileA's data)
Write the modified data to fileB
Close fileB

If you want the data to simply be added to the end of fileB, then you can open the file in "append write" mode and just specify what you want added onto the end.

yeah i got the psuedo...im just struggling with the actual program

Then you need to post the code you have so far and show us where specifically you need help.

Code:

#include <fstream>
#include <iostream>
using namespace std;

int main () {

  char buffer[];
  int size;

  ifstream file_in ("new.txt",ios::in);
  ofstream file_out ("test.txt",ios::out);
  file_in.read (buffer,size);
  file_out.write (buffer,size);
  delete[] buffer;
  file_in.close();
  file_out.close();
  return 0;
}

Hopefully this gives a better idea..... its not full and that hopefully with tinkering would copy the entire contents of one file to another

>> Hopefully this gives a better idea..... its not full and that hopefully with tinkering would copy the entire contents of one file to another

well a start would be some type of structure that would make the program read and write as many times as it takes until the file is copied...

there is a new thing that i saw last month.. it is hidded under keyword

Code:

loop

so with a "loop" and my original pseudo

open fileA
open fileB
start loop_until_EOF
read stringX from fileA
write stringX to fileB
end loop_until_EOF
close fileA and fileB

** not trying to be an @ss, but this smells of homework that not a serious attempt has been made at..

- You need to define size
- You shouldn't delete[] stuff that wasn't created with new[]

I recommend going over the tutorials on this site about file I/O so you can get a better understanding of what's actually going on.

Use the C++ string class instead of character arrays and use operator>> or getline to read in strings instead of read(). Then use operator<< instead of write to write out the strings.