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From: Wes Garland on 20 Apr 2010 11:00
Hi, List!

I have a few simple questions for you:

1 - I there a better place to get help with dash
2 - Is there way to detect that a script is running as dash, instead of a
shell like Solaris' /bin/sh
3 - Corollary to #2, can I expect dash-as-sh to by a hard link or a sym
link? (I would think not, but don't know Debian's policy here)
4 - Reason for #2, is there a way to list all functions declared in a script
with dash? Under Solaris' shell, bash, or the korn shell I can use
"typeset" -- I've searched POSIX and don't see a way that doesn't involve
parsing the script.

Thanks,
Wes

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Wesley W. Garland
Director, Product Development
PageMail, Inc.
+1 613 542 2787 x 102
From: Boyd Stephen Smith Jr. on 20 Apr 2010 11:20
On Tuesday 20 April 2010 09:57:14 Wes Garland wrote:
> 1 - I there a better place to get help with dash

Not that I know of. However, dash is fairly plain when it comes to POSIX-
compliant shells. It handles the stuff POSIX requires it to plus the "local"
keyword (which Debian requires of it) and that is about it.

> 2 - Is there way to detect that a script is running as dash, instead of a
> shell like Solaris' /bin/sh

Not portably. It might be possible by parsing ($SHELL -V -c 'exit 123') or
($SHELL --version -c 'exit 123').

> 3 - Corollary to #2, can I expect dash-as-sh to by a hard link or a sym
> link? (I would think not, but don't know Debian's policy here)

I think it is via symlink. I don't think it uses the alternatives system.

> 4 - Reason for #2, is there a way to list all functions declared in a
> script with dash? Under Solaris' shell, bash, or the korn shell I can use
> "typeset" -- I've searched POSIX and don't see a way that doesn't involve
> parsing the script.

Sorry, I don't even see a good way to tell if a function with a particular
name is defined, but less list all the functions in the current shell
environment.

Bash is still an essential package last I checked. You might simply use
/bin/bash and whatever bash-isms you like.
--
Boyd Stephen Smith Jr. ,= ,-_-. =.
bss(a)iguanasuicide.net ((_/)o o(\_))
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From: Wes Garland on 20 Apr 2010 11:40
Hi, Boyd!

On Tue, Apr 20, 2010 at 11:18 AM, Boyd Stephen Smith Jr. <
bss(a)iguanasuicide.net> wrote:

>
> Not portably. It might be possible by parsing ($SHELL -V -c 'exit 123') or
> ($SHELL --version -c 'exit 123').
>

Say, that's a clever approach, thanks for suggesting it.

Sorry, I don't even see a good way to tell if a function with a particular
> name is defined, but less list all the functions in the current shell
> environment.
>

Can you clarify? Listing all the functions in the current shell environment
solves my issue perfectly.. But less is just a pager, no? Oh, wait, did you
mean "much less list"? In which case, we're in the same boat, but I'm
hoping there is a solution I'm not aware of (even though my hopes are dim :)
)


> Bash is still an essential package last I checked. You might simply use
> /bin/bash and whatever bash-isms you like.
>
>
That would work pretty much everywhere except bone-stock Solaris, where I
have no possibility of recovery -- "/bin/bash: bad interpreter: No such file
or directory". At least if I use /bin/sh as my interpreter, I can always at
the very least output an error message.

I suppose my other alternative is roughly [ -x /bin/bash ] && /bin/bash $0
$* && exit $?, and assume that everywhere-but-solaris has /bin/bash. Hmm.
If debian keeps bash around as a default package, even when dash-is-bin-sh,
then I guess I'm in fairly safe territory in that regard.

Thanks,
Wes

--
Wesley W. Garland
Director, Product Development
PageMail, Inc.
+1 613 542 2787 x 102
From: Vincent Lefevre on 22 Apr 2010 07:10
On 2010-04-20 11:37:31 -0400, Wes Garland wrote:
> > Bash is still an essential package last I checked. You might simply use
> > /bin/bash and whatever bash-isms you like.
> >
> That would work pretty much everywhere except bone-stock Solaris,
> where I have no possibility of recovery -- "/bin/bash: bad
> interpreter: No such file or directory".

That wouldn't even work everywhere under Linux. For instance, bash
isn't installed by default on Maemo.

> I suppose my other alternative is roughly [ -x /bin/bash ] && /bin/bash $0
> $* && exit $?, and assume that everywhere-but-solaris has /bin/bash. Hmm.

[ -x /bin/bash ] && exec /bin/bash -- "$0" ${1+"$@"}

But you also need to detect whether you are not running bash via
this line, otherwise you'll get an infinite loop. I think this can
be done with an environment variable, something like:

[ "$RUNNING_BASH" = yes ] || [ -x /bin/bash ] && \
exec env RUNNING_BASH=yes /bin/bash -- "$0" ${1+"$@"}

(not tested). You can also test features, like in:

( [[ -n 1 && -n 2 ]] ) 2> /dev/null || exec bash -- "$0" ${1+"$@"}

> If debian keeps bash around as a default package, even when
> dash-is-bin-sh, then I guess I'm in fairly safe territory in that
> regard.

It would probably remain as a default package, but I don't see why
it should remain as essential in the long term.

--
Vincent Lef�vre <vincent(a)vinc17.net> - Web: <http://www.vinc17.net/>
100% accessible validated (X)HTML - Blog: <http://www.vinc17.net/blog/>
Work: CR INRIA - computer arithmetic / Ar�naire project (LIP, ENS-Lyon)


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From: Chris Davies on 21 Apr 2010 05:30
Wes Garland <wes(a)page.ca> wrote:
> 2 - Is there way to detect that a script is running as dash, instead of a
> shell like Solaris' /bin/sh

If you write your script portably it will work with /bin/sh, for many
values of sh. If you rely on features of ksh or bash you should specify
one of those shells on the #! line.


> 4 - Reason for #2, is there a way to list all functions declared in a script
> with dash?

"set" works for ksh, bash, and dash. On (at least) Solaris 9 & 10 and
Debian. Is that enough?

Chris


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