| File units (de)allocation in IDL - what is the proper way? [message #93459] |
Fri, 22 July 2016 02:05  |
DAVIDE LENA
Messages: 22
Registered: September 2011
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Junior Member |
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Hello everyone,
when opening files to write outputs I usually do:
OPENW, unit1, 'file1.txt', /GET_LUN
OPENW, unit2, 'file2.txt', /GET_LUN
...
CLOSE, unit1
CLOSE, unit2
FREE_LUN, unit1
FREE_LUN, unit2
However, it seems that closing *and freeing* can be equally achieved with:
CLOSE, unit1, unit2, /ALL
Is this correct? Is there a best practice?
Thanks in advance.
Dave
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| Re: File units (de)allocation in IDL - what is the proper way? [message #93460 is a reply to message #93459] |
Fri, 22 July 2016 02:51  |
Helder Marchetto
Messages: 520
Registered: November 2011
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Senior Member |
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On Friday, July 22, 2016 at 11:05:09 AM UTC+2, Dave wrote:
> Hello everyone,
> when opening files to write outputs I usually do:
>
> OPENW, unit1, 'file1.txt', /GET_LUN
> OPENW, unit2, 'file2.txt', /GET_LUN
> ...
> CLOSE, unit1
> CLOSE, unit2
>
> FREE_LUN, unit1
> FREE_LUN, unit2
>
> However, it seems that closing *and freeing* can be equally achieved with:
>
> CLOSE, unit1, unit2, /ALL
>
> Is this correct? Is there a best practice?
> Thanks in advance.
> Dave
I don't think so.
These commands:
CLOSE, unit1
CLOSE, unit2
are the same as
CLOSE, unit1, unit2
But this command could do much more:
CLOSE, unit1, unit2, /all
In fact it will close *all* open units. And you don't need to specify the units at all. In other words it is equivalent to:
CLOSE, /ALL
Now you should see the problem: If you have other units open, this will close them. So it is only useful if you lost track of open units and you want to close them all... Otherwise you might close units that you don't want to close at all.
I hope this helps.
Cheers,
Helder
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| Re: File units (de)allocation in IDL - what is the proper way? [message #93462 is a reply to message #93459] |
Fri, 22 July 2016 03:43 |
Markus Schmassmann
Messages: 129
Registered: April 2016
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Senior Member |
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On 07/22/2016 11:05 AM, Dave wrote:
> when opening files to write outputs I usually do:
>
> OPENW, unit1, 'file1.txt', /GET_LUN
> OPENW, unit2, 'file2.txt', /GET_LUN
> ...
> CLOSE, unit1
> CLOSE, unit2
>
> FREE_LUN, unit1
> FREE_LUN, unit2
>
> However, it seems that closing *and freeing* can be equally achieved with:
>
> CLOSE, unit1, unit2, /ALL
>
> Is this correct? Is there a best practice?
not correct, CLOSEing a unit doesn't free it's lun, meaning the file is
closed but the lun number is blocked and cannot be allocated for opening
another process.
However, FREE_LUN implies closing a file if it is not already closed.
For the rest, Herders remarks apply - except that FREE_LUN doesn't have
an /ALL keyword.
So, FREE_LUN, unit1, unit2 would be correct, using separate lines is
only necessary if you need to retrieve the EXIT_STATUS.
Markus Schmassmann
https://www.harrisgeospatial.com/docs/understanding__luns_.h tml
https://www.harrisgeospatial.com/docs/FREE_LUN.html
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