I think that you are basically agreeing with me, quibbles about syntax aside.

I was reacting to the idea of "out of memory". That will not happen if the huge file is processed line by line after the FILE open instead of being stored as an array and then processed in memory.

There could be some other problem here that the OP did not show and is completely unknowable to us because it wasn't shown. A 100MB file even under Win32, version XP should be easy to do, even as an in memory array. A FILE handle should not be "re-opened" with an append for multiple writes - that can cause memory problems with the file system. Keep the file handle open and just continue writing.