Make friends with seek and tell, and use a linked list. Here's how:

1. Your file will be composed of variable-length records.
2. Each record will be appended to the end of the file, as nature intended.
3. The first n bytes of each record will contain the packed address of the previously-written record.
4. The first n bytes of the first record (i.e. the first n bytes of the file) will contain the address of the last-written record.

When writing a record,

1. Read the address of the last record from the beginning of the file. Call it $last.
2. seek to the end of the file.
3. Use tell to see where you are. Call this address $next.
4. Write $last to the end of the file, then your data record.
5. seek to the beginning of the file, and write $next there.

When reading the file,

1. Read $last from the beginning of the file.
2. seek to the end of the file, and use tell to get the current address. Call it $next.
3. seek to $last, and read n bytes into the variable $prev.
4. Read $next - $last - n bytes from the file. This is the last unread record.
5. Set $last = $prev and $next = $last.
6. Repeat from step 3. until you've read as many records as you want, or until $last > $next (i.e. you've reached the beginning of the file).

   ---

   In reply to Re: writing to the top of a file by Dr. Mu
   in thread writing to the top of a file by Anonymous Monk

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