Re: [PATCH] * config.sub: Cordon off single-component aliases

[Paul Eggert]

On 05/18/2018 05:42 PM, Ben Elliston wrote:
> ${parameter:-word} is in POSIX, but I don't know how portable it is to
> old Bourne shells.  Paul?

Although it does not work on old Bourne shells, I suspect we don't need 
to worry about them any more.

The "Shellology" section of the Autoconf manual says ${VAR:-VALUE} 
causes old BSD shells to complain and die, and mentions Ultrix. However, 
as far as I know these old shells are now museum pieces. The last Ultrix 
release was in 1995. I haven't fielded an Ultrix bug report for many years.

For what it's worth, 'configure' scripts are still portable to Ultrix 
because they search for a POSIX-compatible shell by trying a list of 
programs that includes 'sh5', which was how Ultrix did it. I think this 
was due to the late Fred Canter, who specialized in getting the farkles 
out.  See:

Hall J. The last farkle. Linux J. 2007-12-02. 
https://www.linuxjournal.com/node/1005779