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Re: [Feature Request]export extglob from environment


From: Chet Ramey
Subject: Re: [Feature Request]export extglob from environment
Date: Sat, 09 May 2009 20:24:49 -0400
User-agent: Thunderbird 2.0.0.21 (Macintosh/20090302)

Raph wrote:
> Hello,
> while trying to export this function :
> ------------------------
> foo() {
>       case "$1" in
>               ?(a))
>                       echo a
>               ;;
>       esac
> }
> ------------------------
> with export -f foo I went into some problem
> as soon as any new instance is launched :
> bash -c "foo bar"     : failed
> xterm &               : failed
> bash -O extglob               : ok
> bash -O extglob -c "xterm"  : failed
> 
> The failure of the new instance is the following :
> -------------------------
> bash: foo: line 1: syntax error near unexpected token `('
> bash: foo: line 1: ` ?(a))'
> bash: error importing function definition for `foo'
> -------------------------
> In fact:
> - $SHELLOPTS doesn't contains extglob

Of course.  It's only designed to transmit options settable with `set -o'
to child processes.

> - $SHELLOPTS is readonly

Yes.  You manipulate those options using set -o.

> - bashrc is evaluated after the environment

How else would settings in startup files override the environment?

> - the environment needs extglob

Not really.  In this particular case, you could have used `xterm -e'
to run bash with the -O extglob option.

> It happens that sometimes you need to export some functions
> without explicitely wanting to add the extglob option.

Maybe.  But you're going to have to parse them somehow.  That's how
function definitions work.  If you want to pass functions through
the environment without parsing the definition, save the text to a
variable and `eval' its value when you want it.

> And alias bash='bash -O extglob' doesn't seem to be clean to me
> (even if possible as a workaround)

It's not.  How would it have helped in your example?

> So the feature request is about a way to set the extglob status
> from the environment.
> Kind of solution though in IRC :
> - shopt -s exportopts
> - shopt -s exportextglob
> - extglob part of $SHELLOPTS
> - load of a kind of .bashrc.env_insensible before anything else

None of these are compelling.  Maybe a BASHOPTS analog to SHELLOPTS
for `shopt' options.  It might be useful to provide a configuration
option that defaults extglob to on, also.

Chet
-- 
``The lyf so short, the craft so long to lerne.'' - Chaucer

Chet Ramey, ITS, CWRU    address@hidden    http://cnswww.cns.cwru.edu/~chet/




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