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Re: error reading file question [message #51200 is a reply to message #51197]

Tue, 07 November 2006 11:08

Paul Van Delst[1]
Messages: 1157
Registered: April 2002

Senior Member

David Groff wrote:
> Is there a way in IDL to check for problems when reading a data file?
> For example in Fortran you would do something like
> Error_Status = Read (filename)
> IF ( Error_Status /= Success ) THEN
> --------------------------(etc.)
>
> If something is wrong with the data file the problem would be discovered
> via error_status.
>
> Thanks

Hello again Dave! :o)

This is how I do it (you can check the netCDF TauProfile read function for more details):

pro test
; Setup error handler
catch, ierr
if(ierr ne 0)then begin
catch, /cancel
message, !error_state.msg + '; Closing file...', /continue
if(n_elements(fileid) ne 0) then free_lun, fileid
return
endif
; Read non-existant file
openr, fileid, 'newfile.dat', /get_lun
x=0.0
readu, fileid, x
free_lun, fileid
print, x
catch,/cancel ; <--- don't forget this
end

IDL> .run test
% Compiled module: TEST.
IDL> test
% TEST: OPENR: Error opening file. Unit: 100, File: newfile.dat; Closing file...

You can also use ON_IOERROR, but that's basically a fancy way of saying GOTO. I reckon the
CATCH method is cleaner.

BTW, this should work for any error. If you want to flag your own errors you can just do
something like:

if( ...some error condition...) then $
message, 'Some error condition occurred', /noname, /noprint

and control will be sent to the CATCH handler.

cheers,

paulv

--
Paul van Delst Ride lots.
CIMSS @ NOAA/NCEP/EMC Eddy Merckx
Ph: (301)763-8000 x7748
Fax:(301)763-8545

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[Message index]

		Re: error reading file question By: David Fanning on Tue, 07 November 2006 13:02
		Re: error reading file question By: Paul Van Delst[1] on Tue, 07 November 2006 12:36
		Re: error reading file question By: David Fanning on Tue, 07 November 2006 11:34
		Re: error reading file question By: Paul Van Delst[1] on Tue, 07 November 2006 11:08
		Re: error reading file question By: David Fanning on Tue, 07 November 2006 06:12

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