From: Guillaume Marcais <guslist@...>
Date: 2005-03-04T07:56:09+09:00
Subject: Re: How/Where is a Stream Stored?

On Thu, 2005-03-03 at 05:26 +0900, Randy Kramer wrote:
> I'm thinking that maybe a stream ("on" the input file?) might be a way to do 
> the backtracking (by moving the pos back from the current position, either 
> one character at a time or several (and then read forward to the first 
> space)).  

It depends on the type of stream. You can backtrack easily with a file,
but you can't with non-seekable stream (like stdin, network socket,
etc.). So using IO#seek would prevent your program to work as a UNIX
filter (reading from stdin, writing to stdout). Might be or not be a
great deal to you, your call...

> I'm wondering how efficient an operation that is--are such stream  operations 
> performed on the disk file itself, or is the stream somehow buffered in 
> memory and the operations performed there.  (Or, am I hopelessly 
> confused? ;-)

All disk operations on recent OS are cached. Backtracking a small amount
is likely not to generate any disk activity.

Guillaume.