| Re: GET_LUN running out of LUNs? [message #31113] |
Thu, 13 June 2002 04:13  |
Niel Malan
Messages: 7
Registered: April 2002
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Junior Member |
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On 12 Jun 2002 16:40:52 -0700, you wrote in comp.lang.idl-pvwave:
> I'm having trouble with GET_LUN and OPENW,
> running out of free units, even though I'm very careful
> to close every unit I open. These are units numbered
> from 100 to 128. I don't remember reading that
> IDL treats them differently than numbers below 100.
>
> Here's are three examples.
Your problem is that the counterpart for GET_LUN is FREE_LUN, and not CLOSE
So:
GET_LUN, unit
OPENR, unit, filename
READF, unit, dummy
CLOSE, unit
FREE_LUN, unit.
Or in shorthand:
OPENR, unit, filename, /GET_LUN
READF, unit, dummy
FREE_LUN, unit ; This works because FREE_LUN automaticall closes the file.
IDL-supplied units range from 100 to 128.
CLOSE, /ALL also frees automatically supplied units, which make your second example work.
To quote from the documentation:
"ALL: Set this keyword to close all open file units. In addition, any file units that were allocated via GET_LUN are freed."
There is not really a need to free the unit in a loop.
Instead of
> FOR i=0,30 do BEGIN
> GET_LUN, unit
> print, i, unit
> close, unit
> ENDFOR
> END
>
use
GET_LUN, unit
FOR i=0,30 do BEGIN
print, i, unit
; OPENR, unit, filename
; READF, unit
; CLOSE, unit
ENDFOR
FREE_LUN, unit
Which will give you the same result as you second example. I am presuming that you will write to the file in the loop.
Rember then, getting a unit is different from opening a file:
OPEN - CLOSE, GET_LUN - FREE_LUN
Niel
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