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Re: fstat, file_info and file_test [message #35217 is a reply to message #35073]

Thu, 15 May 2003 07:56

btt
Messages: 345
Registered: December 2000

Senior Member

Nigel Wade wrote:
> Ben Tupper wrote:
>
>
>> Hello,
>>
>> This appears to be the week for file questions.
>>
>> I see that in the now distant past, my question has been asked here
>> before, but the answers were pre-IDL 5.4 when FILE_xxxxx routines
>> appeared.
>>
>> I would like to have a test that reports if the file is open - by simply
>> providing the filename. FSTAT almost does it, but I have to associate
>> the file with a LUN first. FILE_INFO and FILE_TEST each take the
>> filename as an argument (instead of the lun that FSTAT requires), but
>> neither test for 'openess'.
>>
>> What I would like to have is a function similar to:
>>
>> result = FILE_ISOPEN(filename)
>>
>> that returns a 1 (for open) or a 0 (for closed). Or, perhaps better in
>> the long run, I'd like to see an /ISOPEN keyword added to FILE_TEST.
>>
>>
>> Any suggestions?
>>
>> Thanks,
>> Ben
>
>
> How do you deal with the issue of the file being renamed or deleted after
> you've opened it? What do you do if the file you opened is renamed and new
> file created with the same name - should the test indicate it's open or
> not?
>
> In general, not even the OS can tell you reliably what you want for these
> reasons.
>

Good questions! Another question to add to your list, what happens if
more than one valid pointers exist to the single file? Witness below,
that u1 and u2 are each valid LUNs to the same file. Gaak! I can see
why the underlying OS can't be counted upon for 'truth' - too many cooks!

IDL> get_LUN, u1
IDL> get_LUN, u2
IDL> openW, u1, file
IDL> for i = 0, 2 do print, s[i]
Unit Attributes Name
100 Read, Write, New, Reserved /Users/ben/data.dat
101 Closed, Reserved
IDL> openU, u2, file
IDL> help, /file, output = s
IDL> for i = 0, n_elements(s)-1 do print, s[i]
Unit Attributes Name
100 Read, Write, New, Reserved /Users/ben/data.dat
101 Read, Write, Reserved /Users/ben/data.dat

Thanks,
Ben

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[Message index]

		Re: fstat, file_info and file_test By: Nigel Wade on Thu, 15 May 2003 02:26
		Re: fstat, file_info and file_test By: Karsten Rodenacker on Thu, 15 May 2003 02:19
		Re: fstat, file_info and file_test By: btt on Wed, 14 May 2003 11:28
		Re: fstat, file_info and file_test By: btt on Wed, 14 May 2003 10:48
		Re: fstat, file_info and file_test By: Bruce Bowler on Wed, 14 May 2003 09:56
		Re: fstat, file_info and file_test By: Richard Younger on Wed, 14 May 2003 09:13
		Re: fstat, file_info and file_test By: Richard Younger on Fri, 16 May 2003 11:16
		Re: fstat, file_info and file_test By: btt on Thu, 15 May 2003 07:56

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