From: Tim Heaney <theaney@...>
Date: 2005-01-31T22:20:47+09:00
Subject: Re: perl's -t and -B file tests in ruby?

ts <decoux@moulon.inra.fr> writes:
>
> W> -B : file is binary
>
>  Define what is a binary file ?

In this context, Perl essentially means that the file has a lot of
non-ASCII characters. From the perlfunc man page

    -T  File is an ASCII text file (heuristic guess).
    -B  File is a "binary" file (opposite of -T).

and 

    The "-T" and "-B" switches work as follows.  The
    first block or so of the file is examined for odd
    characters such as strange control codes or char-
    acters with the high bit set.  If too many strange
    characters (>30%) are found, it's a "-B" file,
    otherwise it's a "-T" file.  Also, any file con-
    taining null in the first block is considered a
    binary file.  If "-T" or "-B" is used on a file-
    handle, the current IO buffer is examined rather
    than the first block.  Both "-T" and "-B" return
    true on a null file, or a file at EOF when testing
    a filehandle.  Because you have to read a file to
    do the "-T" test, on most occasions you want to
    use a "-f" against the file first, as in "next
    unless -f $file && -T $file".