Hmm... in that case I think you can just create a multiple input data parameter.

<input type="data" format="tabular" multiple="true" name="inputs"
label="blah" />

You can iterate through the files in your <command> tag and pass them
to your merge.py file:

<command interpreter="python">merge.py #for $input in $inputs# $input
#end for# ...
</command>

This works unless you literally need 9 files - this input type doesn't
support min/max right now. (There is a Trello card that includes
adding such functionality if you want to vote on it
https://trello.com/c/lp5YmA1O).

I hope this helps - let me know if this is not quite right.

-John


On Thu, Aug 21, 2014 at 3:30 PM, George Weingart

<george.weingart@gmail.com> wrote:
> They are totally dynamic.
> Say all the files of tabular type that the User has at the moment.
>
>
> On Thu, Aug 21, 2014 at 12:28 PM, John Chilton <jmchilton@gmail.com> wrote:
>>
>> Are these 17 files fairly dynamic - i.e. are they going to depend on
>> previous steps in a history or user uploads - or are they literally
>> just 17 more or less fixed files associated with that tool and every
>> user should see roughly the same 17 options.
>>
>> -John
>>
>> On Thu, Aug 21, 2014 at 3:03 PM, George Weingart
>> <george.weingart@gmail.com> wrote:
>> > Hello,
>> >
>> >
>> > I would like to get advice how to implement the following application
>> > into
>> > Galaxy:
>> >
>> >
>> > We have a set of say, 17 tabular files,   we would like to present them
>> > to
>> > the User and allow him to select a subset of them,  say 9.
>> >
>> > Once he selected these files we would like to invoke our program
>> > “merge.py”
>> > against the subset of 9 files the User selected whose result is an
>> > output of
>> > one file.
>> >
>> > How would the xml look?
>> >
>> >
>> > Thanks!
>> > George Weingart
>> >
>> >
>> >
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>