Re: How to change the shebang in 'configure' to require Bash

[Eric Blake]

On 03/18/2018 10:39 AM, R. Diez wrote:
> I realise that this decision goes against Autoconf's portability 
> principle. But even as a humble user, I am entitled to some freedom of 
> choice. 8-)
>
> I could write some code in configure.ac to detect the current shell. But 
> is there any way to tell Autoconf to output a Bash shebang in the 
> generated 'configure' script, instead of the standard "#! /bin/sh".

Not any easy way that I know of, precisely because it goes against 
autoconf's portability.  If you're going to write in plain bash rather 
than a portable shell script, then do you need the additional layer of 
autoconf in the first place?

> I read about variable CONFIG_SHELL, but that looks like it's meant for 
> the user. Or can I set that variable inside configure.ac?

If you want to muck in the internals of autoconf, lib/m4sugar/m4sh.m4 
emits the shebang lines during AS_INIT_GENERATED (for subsidiary scripts 
produced by the primary, such as config.status), and during AS_INIT (for 
the primary script, such as configure).  Those macros are not set up to 
easily hook in a replacement, so you'd have to rewrite your m4 library 
to redefine those macros the way you want.  If you think that other 
people would commonly want to hook in a different default shell than 
/bin/sh, you're welcome to turn it into a formal patch against autoconf 
instead of something you just override locally, but I'm not yet 
convinced that it is common to throw away portability.

> Please copy me on all the answers, as I am not subscribed to this 
> mailing list.

It's already list policy to reply-to-all, precisely for that reason.

--
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
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