Replacement for declare in dash?

Replacement for declare in dash?

[Alexander Huemer]

Hi,

I wrote a shell script on a non-Debian system and assumed, in my 
greenness, that testing it with #!/bin/bash --posix would ensure that 
the script would run under dash too. I was wrong. Of course that is the 
fault of bash and not dash.
Here is a simplified form of the script:

#!/bin/dash
# This works when run with #!/bin/bash --posix

func() {
        cat /proc/1/environ
}

sudo sh -c "$(declare -f func); func"

Can I do anything equivalent with dash?
I did not find anything in the docs, but hope dies last.
Of course I can swap the function out in a seperate script, but I'd like 
to avoid that.
Thanks in advance for all ideas.

Kind regards,
-Alex

Re: Replacement for declare in dash?

[Guido Berhoerster]

* Alexander Huemer <alexander.huemer@xx.vu> [2013-10-16 14:26]:
> Hi,
> 
> I wrote a shell script on a non-Debian system and assumed, in my 
> greenness, that testing it with #!/bin/bash --posix would ensure that 
> the script would run under dash too. I was wrong. Of course that is the 
> fault of bash and not dash.
> Here is a simplified form of the script:
> 
> #!/bin/dash
> # This works when run with #!/bin/bash --posix
> 
> func() {
>         cat /proc/1/environ
> }
> 
> sudo sh -c "$(declare -f func); func"
> 
> Can I do anything equivalent with dash?

No.

> I did not find anything in the docs, but hope dies last.

This is even ugly in bash because you're abusing a function as a
variable. And the shell you get with "sudo sh" depends on your
system configuration.
You can embed commands using a here-doc instead of func()...

sudo /bin/dash << "EOF"
cat /proc/1/environ
# ...
EOF

> Of course I can swap the function out in a seperate script, but I'd like 
> to avoid that.

...but this seems to be the right thing to do rather than
embedding a script inside a script.
-- 
Guido Berhoerster

Re: Replacement for declare in dash?

[Chet Ramey]

On 10/16/13 8:18 AM, Alexander Huemer wrote:
> Hi,
> 
> I wrote a shell script on a non-Debian system and assumed, in my 
> greenness, that testing it with #!/bin/bash --posix would ensure that 
> the script would run under dash too. I was wrong. Of course that is the 
> fault of bash and not dash.

Maybe you should have verified your assumptions first.  That is simply not
what the --posix option does.  Posix mode makes bash a superset of Posix;
it's not a nothing-but-what-posix-specifies mode.

Chet

-- 
``The lyf so short, the craft so long to lerne.'' - Chaucer
		 ``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, ITS, CWRU    chet@case.edu    http://cnswww.cns.cwru.edu/~chet/

Re: Replacement for declare in dash?

[Eric Blake]

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On 10/16/2013 08:17 AM, Chet Ramey wrote:
> On 10/16/13 8:18 AM, Alexander Huemer wrote:
>> Hi,
>>
>> I wrote a shell script on a non-Debian system and assumed, in my 
>> greenness, that testing it with #!/bin/bash --posix would ensure that 
>> the script would run under dash too. I was wrong. Of course that is the 
>> fault of bash and not dash.
> 
> Maybe you should have verified your assumptions first.  That is simply not
> what the --posix option does.  Posix mode makes bash a superset of Posix;
> it's not a nothing-but-what-posix-specifies mode.

If you want a shell that does nothing-but-what-posix-specifies, use posh
from the Debian project.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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Re: Replacement for declare in dash?

[Alexander Huemer]

On Wed, Oct 16, 2013 at 10:17:26AM -0400, Chet Ramey wrote:
> On 10/16/13 8:18 AM, Alexander Huemer wrote:
> > Hi,
> > 
> > I wrote a shell script on a non-Debian system and assumed, in my 
> > greenness, that testing it with #!/bin/bash --posix would ensure that 
> > the script would run under dash too. I was wrong. Of course that is the 
> > fault of bash and not dash.
> 
> Maybe you should have verified your assumptions first.  That is simply not
> what the --posix option does.  Posix mode makes bash a superset of Posix;
> it's not a nothing-but-what-posix-specifies mode.

Thanks for your answer and also for the answers of Guido Berhoerster and 
Eric Blake. That's correct, my assumption was wrong. I'll try to use the 
cat << trick, let's see if that works, I won't assume anything at the 
moment ;) Also thanks for the hint regarding posh, I didn't know that.

Kind regards,
-Alex