Where to start. First, what you are trying to do is invalid. Unless you have fixed length records, it is not possible to insert a record into the middle of a text file. That is the case regardless of the language.
You are right that it's not language dependent. It's file system dependent. Most Unix and Windows filesystems where files are just streams of bytes - and there it's not possible to insert records without copying sections of the file. But there are filesystems where files are lists of records - files look a bit like row-based database tables. IIRC, VMS has the ability to use such filesystems.

But the above is just some pedantery, chances the OP is using such a file system are tiny.

In reply to Re^2: Inserting a line in the middle of a text by JavaFan
in thread Inserting a line in the middle of a text by goude

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