[ale] Re: Installing j2se on RHEL 3?

[Michael Hirsch]

On 5/24/05, Jim Popovitch <jimpop at yahoo.com> wrote:
> On Tue, 2005-05-24 at 21:03 -0400, Joe Steele wrote:
> > I think this behavior is controllable.  A vanilla version of tail (from GNU
> > coreutils-5.2.1) can be forced to exhibit the 'obsolete' behavior if the
> > environment contains the variable '_POSIX2_VERSION' set to some value less
> > than 200112.
> >
> > I don't know about RHEL, but FC3 uses a modified tail command so that the
> > only way to get the 'new' behavior is to define '_POSIX2_VERSION' >= 200112
> > and also define POSIXLY_CORRECT in the environment.
> >
> > To get the 'obsolete' behavior, I'd suggest trying:
> > export _POSIX2_VERSION=199209
> 
> Looking at source code for tail.c from RHEL ES3 coreutils-4.5.3 there is
> this comment: (where P is the command line parameters being evaluated,
> and POSIX textual version 1003.1-2001 is represented as the integer
> 200112):
> 
>   /* If P starts with `+' and the POSIX version predates 1003.1-2001,
>      or if P starts with `-N' (where N is a digit), or `-l', then it
>      is obsolescent.  Return zero otherwise.  */
> 
> So, by setting _POSIX2_VERSION=200112 one should expect 'tail -1
> somefile' to barf.  It doesn't.  However, looking further at tail.c
> shows that parse_obsolescent_option() continues after determining
> obsolescence and correctly parses +N, -N despite knowing they are
> obsolete.  (backwards compatibility == good)
> 
> However, if POSIXLY_CORRECT is set in the environment, then tail will
> NOT force the backwards compatibility and the user will get an error
> like this:
> 
>    tail: `-1' option is obsolete; use `-n 1'

Very keen detective work.  For my version of tail the POSIXLY_CORRECT
doesn't seem to matter:

bash-2.05b$ set | grep POSIX
bash-2.05b$  tail -1 .bashrc
tail: `-1' option is obsolete; use `-n 1'
Try `tail --help' for more information.

But the _POSIX2_VERSION variable does seem to solve the problem.

bash-2.05b$  _POSIX2_VERSION=199209 tail -1 .bashrc
export FOO=barbash-2.05b$ 

But the more I look at this system the more I see that it is not in
its pristine state.  I'm no longer convinced that RHEL has the bad
tail, but maybe the administrator compiled his own version.

Thanks everyone,

Michael