On 2001-10-14 at 18:16 +0000, Bart Schaefer wrote:
> The tar completer interprets any of I, j, and y as options that mean to
> use bzip2'd archives.

Just in case ... if writing new scripts, it's advisable to use 'j',
which various tar programs are settling on, migrating away from 'y'.

Hrm, OpenBSD tar(1) uses -I with a parameter for something else:
-----------------------------< cut here >-------------------------------
 -I file    This is a positional argument which reads the names of
            files to archive or extract from the given file,
            one per line.
-----------------------------< cut here >-------------------------------

Unfortunately, some quick googling hasn't turned up any evidence to back
up my assertion re '-j'.  :^(  Ah, hold on, FreeBSD 4 box, tar(1) manual
page, states:
-----------------------------< cut here >-------------------------------
COMPATIBILITY
     The -y is a FreeBSD localism.  The GNU tar maintainer has now choosen -j
     as the offical bzip2(1) compression option in GNU tar 1.13.18 and later.
     The -I option is for compatibility with Solaris's tar.
-----------------------------< cut here >-------------------------------

-- 
Rifles, muskets, long-bows and hand-grenades are inherently democratic
weapons.  A complex weapon makes the strong stronger, while a simple
weapon -- so long as there is no answer to it -- gives claws to the
weak.  -- George Orwell, "You and the Atom Bomb", 1945