On Aug 2, 11:12 am, David Fanning <da...@dfanning.com> wrote:
> Folks,
>
> Thanks for the answer to my last question. Now another.
> My program is failing with a message from HDF_SD_START
> that it is "Unable to start the HDF-SD Interface".
> All other 67 files in the directory have no problems,
> but this 68th file causes the error, which leads me
> to believe this must be a corrupted file of some sort.
>
> But the error message leaves me in the dark. Can you
> suggest other ways I can diagnose the problem? The
> message "Sorry Charlie!" doesn't help me much. :-(
It's not a valid HDF file. So it's either a corrupted HDF file, or not
HDF to begin with.
I find the following function quite useful in cases like this. It
determines whether a given filename exists, has read or write
permission, and whether it is in HDF or netCDF format. It also returns
the file size in bytes.
FUNCTION FILEINFO, FILENAME
;+
; NAME:
; FILEINFO
;
; PURPOSE:
; Return information about a file.
;
; CATEGORY:
; File utilities.
;
; CALLING SEQUENCE:
; RESULT = FILEINFO(FILE)
;
; INPUTS:
; FILE Name of file
;
; OPTIONAL INPUTS:
; None.
;
; KEYWORD PARAMETERS:
; None.
;
; OUTPUTS:
; An anonymous structure containing information about the file.
; The fields in the structure are as follows:
; NAME String containing the name of the file
; EXIST 1 if file exists, 0 otherwise.
; READ 1 if file can be read, 0 otherwise.
; WRITE 1 if file can be written, 0 otherwise.
; HDF 1 if file is HDF format, 0 otherwise
; (0 if HDF API is not available).
; NETCDF 1 if file is netCDF format, 0 otherwise
; (0 if netCDF API is not available).
; SIZE File size in bytes
; (-1 if file does not exist, or if file cannot be read).
;
; OPTIONAL OUTPUTS:
; None
;
; COMMON BLOCKS:
; None
;
; SIDE EFFECTS:
; None.
;
; RESTRICTIONS:
; Requires IDL 5.0 or higher (square bracket array syntax).
;
; EXAMPLE:
;
;;- Check an existing file
;file = filepath('hurric.dat', subdir='examples/data')
;help, fileinfo(file), /structure
;
;;- Check a new file
;file = 'zztest.dat'
;help, fileinfo(file), /structure
;
; MODIFICATION HISTORY:
; Liam.Gumley@ssec.wisc.edu
; http://cimss.ssec.wisc.edu/~gumley
; $Id: fileinfo.pro,v 1.1 2003/06/30 20:27:21 gumley Exp $
;
; Copyright (C) 1999, 2000 Liam E. Gumley
;
; This program is free software; you can redistribute it and/or
; modify it under the terms of the GNU General Public License
; as published by the Free Software Foundation; either version 2
; of the License, or (at your option) any later version.
;
; This program is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
; GNU General Public License for more details.
;
; You should have received a copy of the GNU General Public License
; along with this program; if not, write to the Free Software
; Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
02111-1307, USA.
;-
rcs_id = '$Id: fileinfo.pro,v 1.1 2003/06/30 20:27:21 gumley Exp $'
;- Check arguments
if (n_params() eq 0) then message, 'Usage: RESULT =
FILEINFO(FILENAME)'
if (n_elements(filename) eq 0) then message, 'Argument FILENAME is
undefined'
;- Set default return value
result = {name:'', exist:0L, read:0L, write:0L, hdf:0L, netcdf:0L,
size:-1L}
;- Get file name
result.name = filename[0]
;- Get file existence status
path = (findfile(result.name))[0]
if (path ne '') then result.exist = 1
;- Get expanded file name, file size, and file read status
if (result.exist) then begin
openr, lun, path, /get_lun, error=error
if (error eq 0) then begin
finfo = fstat(lun)
result.name = finfo.name
result.size = finfo.size
result.read = 1
free_lun, lun
endif
endif
;- Get file write status
if (demo_mode() eq 0) then begin
case result.exist of
1 : openu, lun, result.name, /get_lun, error=error
0 : openw, lun, result.name, /get_lun, error=error, /delete
endcase
if (error eq 0) then begin
finfo = fstat(lun)
result.name = finfo.name
if result.exist then result.size = finfo.size
result.write = 1
free_lun, lun
endif
endif
;- Get HDF status
if (result.read and hdf_exists()) then begin
hdfid = hdf_open(result.name, /read)
if (hdfid ne -1) then begin
result.hdf = 1
hdf_close, hdfid
endif
endif
;- Get netCDF status
if (result.read and ncdf_exists()) then begin
catch, error_status
if (error_status ne 0) then goto, ncdf_continue
cdfid = ncdf_open(result.name)
result.netcdf = 1
ncdf_close, cdfid
ncdf_continue:
catch, /cancel
endif
;- Return result to caller
return, result
END
For example, here is what happens with a file which exists, is
readable and writable, but not valid HDF.
$ echo "Hello world" > test.hdf
$ idl
IDL Version 6.2 (linux x86_64 m64). (c) 2005, Research Systems, Inc.
IDL> result = fileinfo('test.hdf')
IDL> help, result, /structure
** Structure <762498>, 7 tags, length=40, data length=40, refs=1:
NAME STRING 'test.hdf'
EXIST LONG 1
READ LONG 1
WRITE LONG 1
HDF LONG 0
NETCDF LONG 0
SIZE LONG 12
Cheers,
Liam.
Practical IDL Programming
http://www.gumley.com/
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